Adolescents more vulnerable to cannabis addiction but not other mental health risks

July 1, 2022

Science Daily/University College London

Adolescents are over three times more vulnerable to developing a cannabis addiction than adults, but may not be at increased risk of other mental health problems related to the drug, finds a new study led by UCL and King's College London researchers.

The study, published today in the Journal of Psychopharmacology, found that adolescents who used cannabis were no more likely to have higher levels of subclinical depression or anxiety than adults who use cannabis, nor were they more vulnerable than adult users to the associations with psychotic-like symptoms.

These findings build on a separate study by the same team, published recently in Psychopharmacology that found adolescents were not more vulnerable to associations between chronic cannabis use and cognitive impairment.

Lead author Dr Will Lawn (UCL Clinical Psychopharmacology Unit and Institute of Psychiatry, Psychology and Neuroscience at King's College London) said: "There is a lot of concern about how the developing teenage brain might be more vulnerable to the long-term effects of cannabis, but we did not find evidence to support this general claim.

"Cannabis addiction is a real issue that teenagers should be aware of, as they appear to be much more vulnerable to it than adults.

"On the other hand, the impact that cannabis use has during adolescence on cognitive performance or on depression and anxiety may be weaker than hypothesised.

"But we also replicated previous work that if someone becomes addicted to cannabis, that may increase the severity of subclinical mental health symptoms. Given adolescents are also at a greater risk of experiencing difficulties with mental health than adults, they should be proactively discouraged from regular cannabis use."

The findings in both papers come from the CannTeen study, funded by the Medical Research Council, which is comparing the effects of regular cannabis use among adolescents and adults, while also comparing to age-matched controls (non-users of cannabis), a completely novel design.

The study involved 274 participants, including 76 adolescents (aged 16 and 17) who used cannabis one to seven days per week, alongside similar numbers of adult (aged 26-29) users, and teenage and adult control (comparison) participants, who all answered questions about their cannabis use over the last 12 weeks and responded to questionnaires commonly used to assess symptoms of mental ill health. The cannabis users in the study, on average, used it four times per week. The adolescent and adult users were also carefully matched on gender, ethnicity, and type and strength of cannabis.

The researchers found that adolescent cannabis users were three and a half times as likely to develop severe 'cannabis use disorder' (addiction) than adult users, a finding which is in line with previous evidence using different study designs. Cannabis use disorder is defined by symptoms such as, among others: cravings; cannabis use contributing to failures in school or work; heightened tolerance; withdrawal; interpersonal problems caused by or exacerbated by cannabis use; or intending to cut back without success. The researchers found that 50% of the teenage cannabis users studied have six or more cannabis use disorder symptoms, qualifying as severe cannabis use disorder.

Among people of any age, previous studies have found that roughly 9-22% of people who try the drug develop cannabis use disorder, and that risk is higher for people who tried it at a younger age. The increased risk of cannabis addiction during adolescence has now been robustly replicated.

The researchers say that adolescents might be more vulnerable to cannabis addiction because of factors such as increased disruption to relationships with parents and teachers, a hyper-plastic (malleable) brain and developing endocannabinoid system (the part of the nervous system that THC in cannabis acts upon), and an evolving sense of identity and shifting social life.

Adolescent users were more likely than adult users or adolescent non-users to develop psychotic-like symptoms, but the analysis revealed that this is because all adolescents, and all cannabis users, are more likely to newly develop psychotic-like symptoms, rather than cannabis affecting the teenagers differently to adults. In other words, there was no adolescent vulnerability, as the increased risk of psychotic-like symptoms was an additive effect (of the two already known risk factors for psychotic-like symptoms, cannabis use and adolescent age), rather than an interaction between age and cannabis use. The researchers say this fits in with prior evidence that cannabis use may increase the likelihood of developing a psychotic disorder such as schizophrenia, but they warn their study did not investigate the risk of clinical psychosis or schizophrenia.

The researchers found that neither teenage nor adult cannabis users were more likely to develop depressive or anxiety symptoms than non-users. Only the adolescents that have severe cannabis use disorder had worse mental health symptoms, but the researchers caution that the small sample size for this group limits their confidence in this finding.

The separate study published in Psychopharmacology found that cannabis users were no more likely to have impaired working memory or impulsivity. Cannabis users were more likely to have poor verbal memory (remembering things said to you); this effect was the same in adults and teenagers, so again there was no adolescent vulnerability. However, the researchers caution that cannabis use could impact school performance during a key developmental stage of life.

The researchers caution that these findings were cross-sectional (only looking at one time point), and that longitudinal analyses of how their participants changed over time are ongoing.

Senior author Professor Val Curran (UCL Clinical Psychopharmacology Unit, UCL Psychology & Language Sciences) said: "Our findings suggest that schools should be teaching pupils more about the risk of addiction to cannabis, which has been neglected in drugs education. Becoming addicted to cannabis is a serious problem in itself, but it can also increase the likelihood of other mental health problems. Teenagers should therefore be informed of their greater risk of addiction."

https://www.sciencedaily.com/releases/2022/07/220701102757.htm

Major uptick reported in cannabis vaping for all adolescents

Largest increases found among high-school seniors, tripling in 2 years from 5 to 14 percent

May 19, 2022

Science Daily/Columbia University's Mailman School of Public Health

Cannabis vaping is increasing as the most popular method of cannabis delivery among all adolescents in the U.S., as is the frequency of cannabis vaping, according to research at Columbia University Mailman School of Public Health. The study found that the frequency of vaping cannabis among adolescents from all demographic groups is reported at six or more times per month, and rising faster than occasional use. Those who vape and smoke nicotine are more than 40 times more likely to also vape and smoke cannabis.

Until now time trends in vaping use had largely been unexamined including trends in use frequency, emerging disparities, and co-occurring use of other substances, which are all critical for surveillance and public health programmatic efforts. The findings are published in the journal Addiction.

"Heavy and frequent use of cannabis is increasing among U.S. adolescents, and vaped systems for products for both cannabis and nicotine are growing in number so understanding the prevalence and patterns of frequent cannabis vaping is important public health information for prevention," said Katherine Keyes, PhD, professor of epidemiology at Columbia Mailman School. "Given rising concerns about cannabis vaping in terms of safety, and potential for transition to cannabis use disorder especially at frequent levels of use, these results indicate a necessity for public health intervention and increased regulation."

The findings are based on the U.S.-based representative annual survey, Monitoring the Future, a population of 51,052 school-attending adolescents. Schools were randomly selected and invited to participate for two years.

Past 30-day frequent cannabis use with vaping increased (2.1 percent to 5.4 percent), while occasional use with vaping rose from 1.2 to 3.5 percent from 2017 to 2019. Past 30-day frequent (3.8 to 2.1 percent) and occasional (6.9 to 4.4 percent) cannabis use without vaping declined. Certain groups, such as Hispanic/Latino or lower socioeconomic status adolescents, experienced particularly notable increases in frequent cannabis use with vaping (e.g., prevalence among Hispanic/Latino adolescents in 2017: 2.2 percent, 2019: 6.7 percent)

According to Keyes, tobacco use and e-cigarettes, as well as binge drinking, are strongly linked to frequent cannabis use -- both vaping and non-vaping. The evidence indicates that young adults who use nicotine, especially through vaporizers, are more likely to subsequently use vaped cannabis.

In fact, adolescents who reported smoking and vaping nicotine on more than 10 occasions of binge drinking, were 42 times and 10 times more likely to report past 30-day cannabis use with vaping, respectively, compared to no use.

"Given that it is easier for adolescents to conceal vaping than cannabis smoking, this mode of cannabis use may facilitate more frequent use," comments Keyes.

Prevalence increased across grades, with the largest burden among high school seniors for whom past-30-day prevalence almost tripled from 5 percent (2017) to 14 percent (2019). The one-year increase in this grade from 2018 to 2019 (7.5 percent to 14 percent) is the second largest one-year increase in any type of substance use prevalence ever tracked by Monitoring the Future.

"This persisting prevalence of daily cannabis use, which in 2020 use was higher than any year since 1981, is of further alarm for several reasons, observes Keyes. "Heavy levels of cannabis use are associated with adverse cognitive and social outcomes for youth, as well as long-term trajectories of drug use that may have adverse health and other consequences."

Also concerning is that high levels of tetrahydrocannabinol (THC) can be delivered through vaping devices, which may lead to dangerous consequences for youth users with lower tolerance.

"In addition, of note, is the evidence that the increases we are seeing in vaping as compared with smoking are concentrated among non-Hispanic white and higher socioeconomic status adolescents, the latter possibly reflecting the higher price point for vaping devices compared with other administration methods, "noted Keyes.

"As cannabis legalization continues across U.S. states, and as products, delivery systems, potency and marketing proliferate within a for-profit industry, increased attention to youth trends, including investment in sustained and evidence-based prevention and intervention, is increasingly urgent."

https://www.sciencedaily.com/releases/2022/05/220519115311.htm

Four-year college students drink more, use marijuana less than community college peers

May 18, 2022

Science Daily/Washington State University

Students at four-year colleges and universities drink nearly twice as much alcohol as their peers in two-year colleges, according to a survey of college students in the Seattle area. On the other hand, students in community colleges and other two-year institutions use marijuana nearly twice as often as four-year students.

The results are detailed in a study led by a Washington State University researcher published in the Journal of American College Health.

"I expected differences in both alcohol and marijuana use among two- and four-year college students, but was surprised by the magnitude of the differences given that the subjects are the same ages," said Jennifer Duckworth, an assistant professor in WSU's Department of Human Development and lead author of the paper.

More research is needed to understand why these differences in alcohol and cannabis use exist, but perceptions of peer use may be one factor. Specifically, four-year students thought their peers drank more than two-year students believed their peers drank, whereas two-year students thought that their peers used cannabis more than four-year students thought their peers did.

In the study, the authors found that, among college students near Seattle, four-year students averaged over seven drinks per week, while two-year students averaged around 3.5 drinks each week, based on a self-reported questionnaire.

For marijuana use, two-year students averaged using it on over eight days in the previous month, while four-year students averaged nearly 4.5 days of use.

Both groups reported experiencing consequences of their substance use, Duckworth said.

The study included 517 students who reported drinking in the past year and who were between the ages of 18-23 at two- and four-year schools in Washington state. The young adults in the study filled out confidential online monthly surveys and received a stipend for participation. That combination of confidentiality, financial incentive, and ease of use led to a very high retention rate, Duckworth said.

She hopes to take the results of this study and conduct additional research on two-year students.

"Two-year students are a much harder group to study because they tend to have more variability in terms of age, work status, and they are more likely to be from underrepresented racial and/or ethnic minority groups," Duckworth said. "We know a lot more about four-year students, at least partly because most of the people doing the research are on four-year campuses."

Many four-year schools have research-based intervention programs to decrease the use of alcohol. She hopes to expand those to two-year campuses as well.

One such tool is a normative feedback intervention, which focuses on correcting misconceptions -- in this case misconceptions students have about peer substance use. Studies have shown that four-year students think their peers are using substances much more than they really are.

"If you think your peers are drinking more than they really are, that leads you to drink more," said Duckworth, who hopes to create and implement something similar for two-year students and marijuana use.

"Two-year students are using marijuana more than four-year students, but they also think their peers are using it more than they probably are," she said. "I say probably because we need more research to assess peer use. It's an important next step is studying this often understudied population."

https://www.sciencedaily.com/releases/2022/05/220518130707.htm

Treatment for substance use reduces depression for many adolescents and young adults with both problems

When adolescents with substance use problems and depression are treated for substance use, about a third also have early improvements in depression

March 29, 2022

Science Daily/Elsevier

A study in the Journal of the American Academy of Child and Adolescent Psychiatry (JAACAP), published by Elsevier, reports that, among youth with substance use and depression, a significant proportion show early improvements in depression during their treatment for substance use. Youth who are using cannabis less frequently prior to treatment and those without conduct disorder are more likely to experience early depression improvement.

"The combination of alcohol or cannabis use and depression is a significant problem in adolescents and young adults. In addition to the negative outcomes associated with substance use, like automobile accidents and academic problems, those with both conditions tend to have longer episodes of depression, more substance-related problems, and, most importantly, an increased risk for suicidal behavior," said lead author John Curry, PhD, Professor Emeritus in the Department of Psychiatry & Behavioral Sciences at Duke University, Durham, NC. "Yet there is no standard approach to treating them, and they are often treated in two separate systems of care."

Earlier studies have shown that some of these young people will show significant improvement in depression during treatment for substance use alone, suggesting that if that improvement is sustained, they may not need additional depression treatment. Based on this evidence, the researchers tested an adaptive approach in which everyone received substance use treatment. Yet, if they were still depressed after a month, they would receive additional depression treatment either with the same therapist or in the community.

"This approach allowed us to examine two different approaches to depression treatment for youth with substance use," said Dr. Curry. "We also wanted to discover what proportion of the youth would have an early depression response during substance use treatment and what factors predicted it."

Across two sites, a sample of 95 youths between the ages of 14 and 21 with alcohol or cannabis use and depressive symptoms received up to 12 sessions of cognitive behavior therapy (CBT) for substance use over 14 weeks. Before treatment, they completed measures of psychiatric diagnoses, alcohol or cannabis use, and severity of depression. Early depression response was defined as a 50% reduction in symptoms by week 4 of treatment. Those without early depression response were randomized to add either CBT for depression with the same therapist or depression treatment in the community.

Thirty-five participants (37%) demonstrated early depression response. Predictors of early depression response were lower frequency of cannabis use at baseline and lack of a conduct disorder diagnosis. No other variables -- including demographic characteristics, severity of depression, or other psychiatric diagnoses -- were predictors. Frequency of drinking, heavy drinking, and cannabis use declined over the full course of treatment for all participants. Among those without early depression response, depression improved significantly with either additional CBT or community treatment, with no difference between treatments.

"This treatment study emphasizes the importance of recognizing the heterogeneity of youth with substance use and co-occurring disorders such as depression, including the different trajectories of their responses to treatment," said lead author Yifrah Kaminer, MD, MBA, Professor Emeritus of Psychiatry at the University of Connecticut, Storrs, CT. "An important finding is that the level of cannabis use affects the trajectory of change in depression during treatment. Additional examination of potential biological markers or other predictors of treatment response is of paramount importance for developing cost-effective interventions."

Additional analyses will examine the course of depression and substance use after treatment, and whether the young people whose depression responded to substance use treatment continue to remain less depressed. Given the relatively small sample, it will be important to replicate the study's findings in other samples. Future research is needed to investigate the factors that underlie the relationship between substance use and depression over time.

https://www.sciencedaily.com/releases/2022/03/220329114730.htm

Early cannabis use linked to heart disease

April 12, 2021

Science Daily/University of Guelph

Smoking cannabis when you're young may increase your risk of developing heart disease later, according to a recent University of Guelph study.

In the first study to look at specific risk indicators for cardiovascular disease (CVD) in young, healthy cannabis users, researchers found subtle but potentially important changes in heart and artery function.

Cigarette smoking is known to affect cardiovascular health, causing changes to blood vessels and the heart. Less is known about the impact of smoking cannabis on long-term CVD risk, even as use of the substance grows in Canada and abroad. Cannabis is the most commonly used recreational substance worldwide after alcohol.

"Cannabis is really widely used as a recreational substance all around the world and is becoming increasingly so," said Christian Cheung, a PhD student in the Human Performance and Health Research Lab, part of the Department of Human Health and Nutritional Sciences (HHNS). "Scientists haven't done that research with cannabis."

Cheung is the lead author of the study, published recently in the Journal of Applied Physiology. His co-authors were Dr. Jamie Burr and Dr. Philip Millar, both professors in HHNS and PhD student Alexandra Coates.

The team studied 35 subjects aged 19 to 30, half of whom were cannabis users. For all subjects, they used ultrasound imaging to look at the heart and arteries. They measured arterial stiffness and arterial function, or the ability of arteries to appropriately expand with greater blood flow. All three measures are indicators of cardiovascular function and potential disease risk.

Arterial stiffness was greater in cannabis users than in non-users. The team measured how fast a pressure wave travelled down the artery; stiffer arteries transmit a wave more quickly.

In cannabis users, cardiac function -- inferred from how the heart moves as seen in echocardiographic images -- was lower than in non-users.

Cheung said the team was surprised to see no difference in artery dilation in response to changing blood flow.

All three measures normally change in cigarette smokers, with stiffer arteries and lower vascular and heart function.

"We don't yet know why in cannabis users there's no difference in vascular function," he said.

Cheung said differences may reflect variations in how tobacco and cannabis are consumed, as well as amounts and frequency and the user's age.

"We looked at young cannabis users. In the cigarette literature, heavy, long-term smokers show reduced vascular function but that's not necessarily the case for younger smokers."

The U of G researchers plan further studies to learn about potential impacts of these changes and disease risk in people who use cannabis.

"This is exciting new data, suggesting that even before more overt signs and symptoms of cardiovascular disease are present, there may be more subtle indications in altered physiological function," said Burr.

"It also paves the way to our next studies, aimed at understanding the direct effects of cannabis consumption, and how this may interact with common stressors of everyday life, like exercise."

Cheung emphasized that few studies have been done on the impacts of cannabis use on cardiovascular health.

"This is an exciting field of research given the ubiquity of cannabis use and the knowledge gap that exists, it's a field ripe with opportunity."

https://www.sciencedaily.com/releases/2021/04/210412114842.htm

Nearly third of US young people prescribed psychoactive drugs admit misusing them

Stimulants and tranquillisers more frequently misused than opioids

February 2, 2021

Science Daily/BMJ

Nearly a third of US teens and young adults prescribed a psychoactive drug misuse that drug, with the likelihood of misuse rising with age, suggests an analysis of national survey responses published in the online journal Family Medicine & Community Health.

Stimulants and tranquillisers were more likely to be misused than opioids, the findings indicate.

Drug overdose is a leading cause of unintentional death in the US, most cases of which involve opioid painkillers, but not all.

Data on the misuse of other prescription psychoactive drugs are few and far between. And every year more than 1 in 3 teens and young adults in the US is prescribed one of these drugs.

To plug this knowledge gap, the researchers drew on the responses of 110,556 US 12-25 year olds who took part in the 2015-2018 National Survey of Drug Use and Health Sampling.

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Overall, around a third (35%) said they had taken a prescribed psychoactive drug in the past year, and a similar proportion (31%) said they had misused that drug.

While opioids were the most commonly prescribed drug, misuse of stimulants and tranquillisers was higher, with nearly 45% of users admitting to this.

One in 10 respondents said they took at least two prescribed psychoactive drugs, with nearly 6 in 10 (58%) confessing to misusing one of these. And 87% admitted to misusing another substance, such as alcohol, cigarettes, cigars, marijuana, cocaine, heroin, inhalants, or hallucinogens.

Use and misuse of a prescribed psychoactive drug increased with age. While one in four teens (12-17 year olds) reported taking any psychoactive prescribed drug over the past year, and around 6% reported taking at least two such drugs, this increased to 41% and 13.5%, respectively, among 18-25 year olds.

Among the teen users of psychoactive prescription drugs, opioids were the most frequently used (19%) followed by stimulants (7%), tranquillisers (4%) and sedatives (2%).

Around 1 in 5 users of prescribed psychoactive drugs said they misused them, with tranquillisers most often misused (40%), followed by stimulants (24%), opioids (nearly 18%), and sedatives (14%).

Among 18-25-year-olds prescribed psychoactive drugs in the past year, 35% reported misuse of at least one drug. And among those prescribed at least two of these drugs, 61% reported misuse and just under 94% reported concurrent use of another substance.

Analyses of the responses from the 18-25-year-olds revealed that, compared with those who had never touched other substances, misuse of psychoactive prescription drugs increased in tandem with more recent use of these substances and number used.

Among 18-25 year-olds, opioids were again the most commonly prescribed psychoactive drug (30%), followed by stimulants (14%), tranquillisers (11.5%) and sedatives (3.5%).

The estimated proportion of misuse in this age group was highest for tranquillisers (45%) followed by stimulants (51%), opioids (23%) and sedatives (19%).

This is an observational study, and therefore can't establish cause, added to which the researchers acknowledge that the study was based on self report; the time frames over which some variables were measured weren't consistent; and misuse was very broadly defined.

Nevertheless, they conclude that the overlap in the profiles of those who use for medical reasons and those who misuse is a strong indicator of how likely they are to abuse psychoactive drugs.

"It is important to monitor the diversity of medication misuse behaviours among youth and young adults, given their potential for abuse liability," they write.

"Modifiable risk factors for prescription substance misuse, such as tobacco and other non-prescription substance use, underscore the need for comprehensive approaches towards health promotion among youth and young adults," they add.

They note that 11.5% of the 18-25 year olds reported serious psychological distress, which was consistently associated with misuse of every psychoactive prescription drug assessed.

"Mental health and medical providers would benefit from using a team approach and having open communication with other healthcare providers to ensure evidence-based guidelines are used when assessing for, and treating, mental health and substance use difficulties," they conclude.

https://www.sciencedaily.com/releases/2021/02/210202192756.htm

Frequent cannabis use by young people linked to decline in IQ

January 28, 2021

Science Daily/RCSI

A study has found that adolescents who frequently use cannabis may experience a decline in Intelligence Quotient (IQ) over time. The findings of the research provide further insight into the harmful neurological and cognitive effects of frequent cannabis use on young people.

The paper, led by researchers at RCSI University of Medicine and Health Sciences, is published in Psychological Medicine.

The results revealed that there were declines of approximately 2 IQ points over time in those who use cannabis frequently compared to those who didn't use cannabis. Further analysis suggested that this decline in IQ points was primarily related to reduction in verbal IQ.

The research involved systematic review and statistical analysis on seven longitudinal studies involving 808 young people who used cannabis at least weekly for a minimum of 6 months and 5308 young people who did not use cannabis. In order to be included in the analysis each study had to have a baseline IQ score prior to starting cannabis use and another IQ score at follow-up. The young people were followed up until age 18 on average although one study followed the young people until age 38.

"Previous research tells us that young people who use cannabis frequently have worse outcomes in life than their peers and are at increased risk for serious mental illnesses like schizophrenia. Loss of IQ points early in life could have significant effects on performance in school and college and later employment prospects," commented senior author on the paper Professor Mary Cannon, Professor of Psychiatric Epidemiology and Youth Mental Health, RCSI.

"Cannabis use during youth is of great concern as the developing brain may be particularly susceptible to harm during this period. The findings of this study help us to further understand this important public health issue," said Dr Emmet Power, Clinical Research Fellow at RCSI and first author on the study.

https://www.sciencedaily.com/releases/2021/01/210128134755.htm

Cognitive behavioral therapy reduces insomnia symptoms among young drinkers

Pilot study shows sleep therapy also reduces alcohol-related issues among those who binge drink

October 20, 2020

Science Daily/University of Missouri-Columbia

More than half of young adults at risk for alcohol-related harm report symptoms of insomnia. Cognitive behavioral therapy (CBT) is one of the first-line treatments for insomnia, but it's never been tested on young adults who are actively drinking. Researchers from the University of Missouri School of Medicine conducted a pilot study to evaluate CBT's effect on young adult binge drinkers with insomnia to determine if this treatment can improve their sleep and potentially affect alcohol use outcomes.

"The potential for insomnia treatment to influence alcohol-related consequences has significant implications for the prevention and treatment of alcohol use among young adults," said Mary Beth Miller, PhD, assistant professor of clinical psychiatry at the MU School of Medicine. "Given the stigma associated with mental health issues and addiction, it's crucial to identify other forms of treatment that either influence alcohol outcomes or open the door to alcohol-related treatment."

Miller tested CBT in a pilot study of 56 people between 18 and 30 years old who reported at least one binge-drinking episode in the past month. Binge drinking was defined as four or more drinks in one occasion. Participants were randomly assigned to either five weekly sessions of CBT -- a behavioral therapy program that focuses on changing patterns of thinking and behavior -- or a single session on sleep hygiene, which focuses on creating optimal sleeping conditions and establishing a bedtime routine. The CBT session topics included sleep hygiene, sleep restriction, relaxation techniques, behavioral experiments, insomnia prevention discussions and sleep diary use. All participants wore wrist devices to objectively measure sleep and completed subjective daily sleep and drinking surveys.

Results showed CBT participants reported a 56% reduction in insomnia severity, compared to a 32% reduction in symptoms for those who completed only the sleep hygiene session. The CBT participants also showed moderate improvement in objectively assessed sleep efficiency after treatment compared to the sleep hygiene participants. Both groups reduced their drinks per week and alcohol-related consequences after treatment. However, CBT participants reported greater improvements in insomnia, which in turn were associated with reductions in alcohol-related problems.

"The results of this study indicate that insomnia treatment may improve alcohol-related problems, and therefore, may be an ideal first step toward treatment among binge-drinking young adults with insomnia," Miller said.

Miller believes the data collected in this study warrants a larger sample size study looking at alcohol-related problems as a primary outcome. She plans to determine if insomnia treatment improves executive function and the ability to regulate emotions, which in turn might decrease risk for alcohol-related problems.

https://www.sciencedaily.com/releases/2020/10/201020131347.htm

Cannabis ads and store location influence youth marijuana use

October 8, 2020

Science Daily/Washington State University

States may want to consider the proximity of cannabis retailers and cannabis advertising to neighborhoods to prevent underage use of the drug, according to new researc

Advertising and location of cannabis retailers influence adolescents' intentions to use marijuana, according to a new study in the Journal of Health Communication by Washington State University researchers.

Stacey J.T. Hust, associate dean in the Murrow College of Communication, and Jessica Fitts Willoughby, associate professor of communication, conducted a survey of 13- to 17-year-olds in Washington State to find out how marijuana advertising and the location of marijuana retailers influence adolescents' intentions to use the drug. The researchers also asked participants about their outcome beliefs -- whether or not they thought using marijuana would be good for them personally and or socially.

Their research shows regular exposure to marijuana advertising on storefronts, billboards, retailer websites and other locations increased the likelihood of adolescents using marijuana.

"While there are restrictions against using advertising designed specifically to target youth, it does still appear to be having some influence," Willoughby said. "Our research suggests a need to equip adolescents with the knowledge and skills to critically evaluate marijuana advertisements."

Location of retail stores also played a role but the results of the survey were mixed.

While the actual density of marijuana retailers in an area was not associated with adolescents' intentions to use, study participants who said they lived within five miles of a marijuana shop were more likely to report intentions to use the drug than those who perceived they lived farther away.

"This was especially the case when they also reported having positive beliefs about marijuana use," Hust said. "The study participants who felt positively about marijuana and perceived living close to retailers were the most likely to report intentions to use marijuana."

The results of the research team's study could have significant policy implications as states that have legalized recreational marijuana use grapple with ways to adhere to the drug's legal status while trying to prevent adolescent marijuana use.

For instance, most states with legalized marijuana restrict placing retailers and advertisements next to schools, but other locations, where adolescents live and spend a lot of their time, remain largely unregulated.

"Our findings are particularly relevant given that most states that have legalized recreational marijuana have not restricted their proximity to neighborhoods or living areas, which may be particularly challenging in large metropolitan areas," Hust said. "States may want to consider using census data to identify the proportion of teens living in particular areas as they identify the location for marijuana retailers."

The researchers are currently in the process of conducting a new experiment where they are testing different types of advertisements to see how young people interpret and respond to them.

"One of the things this research and other studies suggest is that these advertisements are pretty prolific in certain areas and we want to see what type of appeals are used in the advertisements and how those appeals affect viewers," Hust said. "Our long-term goal is really to develop a better understanding of how adolescents can make heathy and informed decisions in an environment in which marijuana is legal."

https://www.sciencedaily.com/releases/2020/10/201008142132.htm

Sweet coolers a gateway to increased alcohol consumption

July 22, 2020

Science Daily/University of Guelph

It might be no surprise that sugar in sweetened coolers helps to mask the taste of alcohol and make it more appealing to novice consumers, including young people.

Based on the first study to look at the role of high-fructose corn syrup -- the main ingredient in most coolers -- a University of Guelph professor suggests that these sweetened beverages can actually promote harmful alcohol consumption.

The results should prompt caution particularly among university-age drinkers and their parents about the potential of coolers to encourage consumption of other alcoholic beverages, said psychology professor Francesco Leri.

"The more sweetened drinks that an adolescent drinks, the more likely they are to drink alcohol that is not sweetened," said Leri, who conducted the study with master's student Samantha Ayoub and psychology professor Linda Parker

As with earlier studies of how sweetened alcoholic beverages affect adolescent drinking behaviour, he said, this study suggests that these beverages act as "a gateway -- a way to get introduced and then like alcohol itself."

Other researchers have found that sweeteners such as sucrose and glucose encourage rats to drink more alcohol.

Published recently in the journal Alcohol, the U of G study is the first to look at the effects of high-fructose corn syrup (HFCS), which makes up about one-quarter of the volume of many sweetened alcoholic beverages.

Using rats able to self-administer liquids, the researchers tested consumption of different proportions of alcohol mixed with 25-per-cent HFCS. Adding the corn syrup increased rats' intake and the palatability of the beverage. Palatability was measured by observing behaviours such as rats licking their snouts. Rats given alcohol normally show facial signs of disgust.

"Most rats don't voluntarily drink alcohol by itself. The moment we added HFCS, there was a huge increase in consumption," said Leri.

Beverages containing 10 per cent alcohol and 25 per cent corn syrup encouraged some rats to drink an amount equivalent to an average adult human consuming 4.5 beers in 30 minutes. Although the researchers didn't measure blood alcohol levels, consuming that much alcohol would cause blood alcohol levels in people to spike to "binge drinking" amounts.

Mixing alcohol with saccharin (a non-caloric sweetener) also prompted more consumption but less than with HFCS.

In earlier studies, Leri looked at the effects of HFCS on the brain. This time, he wanted to see how sweeteners might affect consumption of other addictive drugs such as alcohol.

He said someone drinking sweetened coolers can grow accustomed to the taste of alcohol, even if they initially dislike the latter on its own.

"Most people that don't like the taste of alcohol in a drink will drink sweetened coolers. We think they get an introduction to alcohol via sweeteners."

Leri said beverage manufacturers might be persuaded to use more natural sweeteners such as regular cane sugar or to refrain from marketing their products to younger consumers.

He encourages parents to discuss coolers with young people.

"Because it's sweet and tastes like pop doesn't make it any safer than a straight can of beer or glass of wine. Alcohol is alcohol no matter what. Because alcohol is sweet, there's a danger of over-drinking. It's important to monitor the amount taken, especially when it's mixed with other substances. It's just another drug of addiction, that's all it is."

https://www.sciencedaily.com/releases/2020/07/200722142746.htm

Marijuana use while pregnant boosts risk of children's sleep problems

Negative effects seen as much as a decade later

July 2, 2020

Science Daily/University of Colorado at Boulder

As many as 7% of moms-to-be use marijuana while pregnant, and that number is rising fast as more use it to quell morning sickness. But new research suggests such use could have a lasting impact on the fetal brain, influencing children's sleep for as much as a decade.

Use marijuana while pregnant, and your child is more likely to suffer sleep problems as much as a decade later, according to a new University of Colorado Boulder study of nearly 12,000 youth.

Published in Sleep Health: The Journal of The National Sleep Foundation, the paper is the latest to link prenatal cannabis use to developmental problems in children and the first to suggest it may impact sleep cycles long-term.

It comes at a time when -- while the number of pregnant women drinking alcohol and smoking cigarettes has declined in the United States -- It has risen to 7% of all pregnant women as legalization spreads and more dispensaries recommend it for morning sickness.

"As a society, it took us a while to understand that smoking and drinking alcohol are not advisable during pregnancy, but it is now seen as common sense," said senior author John Hewitt, director of the Institute for Behavioral Genetics at CU Boulder. "Studies like this suggest that it is prudent to extend that common sense advice to cannabis, even if use is now legal."

A landmark study

For the study, Hewitt and lead author Evan Winiger analyzed baseline data from the landmark Adolescent Brain and Cognitive Development (ABCD) study, which is following 11,875 youth from age 9 or 10 into early adulthood.

As part of an exhaustive questionnaire upon intake, participants' mothers were asked if they had ever used marijuana while pregnant and how frequently. (The study did not assess whether they used edibles or smoked pot). The mothers were also asked to fill out a survey regarding their child's sleep patterns, assessing 26 different items ranging from how easily they fell asleep and how long they slept to whether they snored or woke up frequently in the night and how sleepy they were during the day.

About 700 moms reported using marijuana while pregnant. Of those, 184 used it daily and 262 used twice or more daily.

After controlling for a host of other factors, including the mother's education, parent marital status and family income and race, a clear pattern emerged.

"Mothers who said they had used cannabis while pregnant were significantly more likely to report their children having clinical sleep problems," said Winiger, a graduate student in the Department of Psychology and Neuroscience.

Those who used marijuana frequently were more likely to report somnolence symptoms (symptoms of excess sleepiness) in their children, such as trouble waking in the morning and being excessively tired during the day.

The authors note that, while their sample size is large, the study has some limitations.

"We are asking mothers to remember if they smoked marijuana 10 years ago and to admit to a behavior that is frowned upon," said Winiger, suggesting actual rates of prenatal use may have been higher.

While the study doesn't prove that using cannabis while pregnant causes sleep problems, it builds on a small but growing body of evidence pointing to a link.

For instance, one small study found that children who had been exposed to marijuana in-utero woke up more in the night and had lower sleep quality at age 3. Another found that prenatal cannabis use impacted sleep in infancy.

And, in other previous work, Hewitt, Winiger and colleagues found that teenagers who frequently smoked marijuana were more likely to develop insomnia in adulthood.

The fetal brain on THC

Researchers aren't sure exactly how cannabis exposure during vulnerable developmental times might shape future sleep. But studies in animals suggest that THC and other so-called cannabinoids, the active ingredients in pot, attach to CB1 receptors in the developing brain, influencing regions that regulate sleep. The ABCD study, which is taking frequent brain scans of participants as they age, should provide more answers, they said.

Meantime, mothers-to-be should be wary of dispensaries billing weed as an antidote for morning sickness. According to CU research, about 70% of Colorado dispensaries recommend it for that use. But mounting evidence points to potential harms, including low birth weight and later cognitive problems. With marijuana on the market today including far higher THC levels than it did a decade ago, it's impacts on the fetal brain are likely more profound than they once were.

"This study is one more example of why pregnant women are advised to avoid substance use, including cannabis," said Hewitt. "For their children, it could have long-term consequences."

https://www.sciencedaily.com/releases/2020/07/200702153700.htm

Medicinal cannabis may reduce behavioral problems in kids with intellectual disabilities

June 24, 2020

Science Daily/Murdoch Childrens Research Institute

Cannabidiol, a type of medicinal cannabis, may reduce severe behavioural problems in children and adolescents with an intellectual disability a new study has found.

The pilot study, led by the Murdoch Children's Research Institute (MCRI) and published in the British Journal of Clinical Pharmacology, recorded a clinically significant change in participants' irritability, aggression, self-injury, and yelling. The intervention was also found to be safe and well-tolerated by most study participants.

The randomised controlled trial involved eight participants, aged 8-16, years who took either cannabidiol or a placebo over eight weeks. Participants were recruited from paediatric clinics from both hospital and private paediatric practices.

Although the pilot study was not large enough to make definitive statements, the early findings strongly support a larger follow-up trial. Only a large scale randomised controlled trial can produce the definitive results necessary to drive changes in prescribing and clinical care guidelines. The researchers are planning a large study to definitively test the findings.

The researchers are also seeking funding for further research into the effectiveness of medicinal cannabis in children with developmental disorders such as autism and Tourette syndrome.

Associate Professor Daryl Efron, a clinician-scientist at MCRI who led the study, said this was the first investigation of cannabidiol to manage severe behavioural problems in children and adolescents with an intellectual disability. Most of the participants also had autism.

The study found the medication was generally well-tolerated and there were no serious side effects reported. All parents reported they would recommend the study to families with children with similar problems.

Associate Professor Efron said severe behavioural problems such as irritability, aggression and self-injury in children and adolescents with an intellectual disability were a major contributor to functional impairments, missed learning opportunities and reduced quality of life.

He said conventional psychotropic medications, including anti-psychotics and anti-depressants, were prescribed by Australian paediatricians for almost half of young people with an intellectual disability, despite limited evidence of their effectiveness. Given how extremely difficult behavioural problems were to treat in these patients, new, safer interventions were needed to treat this highly vulnerable patient group, he said.

"Current medications carry a high risk of side-effects, with vulnerable people with intellectual disability being less able to report side-effects," he said. "Common side-effects of antipsychotics, such as weight gain and metabolic syndrome, have huge health effects for a patient group already at increased risk of chronic illness."

Cannabidiol is already being used increasingly to manage a range of medical and psychiatric conditions in adults and epilepsy in children.

Associate Professor Efron said there was intense interest from parents and physicians in medicinal cannabis as a treatment for severe behavioural problems in youth with an intellectual disability.

"Parents of children with an intellectual disability and severe behavioural problems are increasingly asking paediatricians whether they can access medicinal cannabis for their child and some parents have reported giving unregulated cannabis products to their children," he said.

"We are also finding many physicians feel unprepared to have these conversations with their patients." Researchers from The Royal Children's Hospital, the University of Melbourne and Monash University also contributed to the study.

https://www.sciencedaily.com/releases/2020/06/200624100039.htm

Minimum legal age for cannabis use should be 19

May 13, 2020

Science Daily/BMC (BioMed Central)

The optimal minimum legal age for non-medical cannabis use is 19 years of age, according to a study published in BMC Public Health.

A team of researchers at the Memorial University of Newfoundland, Canada, investigated how Canadians who started using cannabis at several young ages differed across important outcomes (educational attainment, cigarette smoking, self-reported general and mental health) in later-life.

Dr Hai Nguyen, lead author of the study said: "Prior to legalisation, the medical community recommended a minimum legal age of 21 or 25 for non-medical cannabis use in Canada. This recommendation was based on scientific evidence around the potential adverse impacts of cannabis on cognitive development. However, policymakers feared a high minimum legal age may lead to large underground markets, with those under the legal age continuing to use cannabis illegally. Ultimately, a lower legal age of 18 or 19 was decided across provinces, however there remains ongoing debate and calls to raise the legal age to 21."

To determine whether the age at which people begin to use cannabis may have an impact on later-life outcomes, the authors analysed data from nationally-representative Canadian Tobacco Use Monitoring Surveys (CTUMS) and Canadian Tobacco, Alcohol and Drugs Surveys (CTADS) conducted between 2004 and 2015, which annually interview up to 20,000 individuals aged 15 years and older.

The authors found different optimal minimum legal ages depending on the outcome of interest. For smoking, respondents who first used cannabis aged 19-20 were less likely to smoke cigarettes later in life than those who first used cannabis aged 18, but no significant difference was found in those who started using cannabis at an older age, indicating an optimum legal age of 19.

The number of respondents reporting a high level of completed education was 16% higher among those who first used cannabis between the ages of 21 and 24, relative to those who first used it before age 18, suggesting an optimal minimum legal age of 21.

General health was significantly better among those who started using cannabis aged 18, relative to those who started before age 18, but no significant difference was found among those who started at an older age, suggesting a minimum legal age of 18. However, mental health outcomes were found to be higher among those who first used cannabis aged 19-20 than before age 18, suggesting a minimum legal age of 19.

Dr Nguyen said: "The lower level of completed education reported in those who first used cannabis at an earlier age may reflect poor neurological development or a higher 'drop-out' rate from further education. It is also possible that those who initiate cannabis use early may use it as a gateway for further illicit drug use, resulting in poorer health in later life, which may explain the poor general or mental health scores recorded in the study."

Dr Nguyen said: "Taking into account all measured outcomes, our results indicate that, contrary to the Canadian federal government's recommendation of 18 and the medical community's support for 21 or 25, 19 is the optimal minimum legal age for non-medical cannabis use. Keeping the legal age below 21 may strike a balance between potential increases in underground markets and illegal use, and avoiding the adverse outcomes associated with starting to use cannabis at an earlier age."

The authors caution that as the study used self-reported data, respondents may not have accurately recalled the age at which they first used cannabis. Data was also collected prior to legalization of non-medical cannabis in Canada and the authors were unable to predict the impact of cannabis use after legalization. They suggest that further research is needed to establish potential causal effects between the age at which cannabis is first used and the outcomes measured in the study, and could also focus on additional outcomes such as driving behaviours and street drug use.

https://www.sciencedaily.com/releases/2020/05/200513200400.htm

Early exposure to cannabis boosts young brains' sensitivity to cocaine

April 20, 2020

Science Daily/The Zuckerman Institute at Columbia University

Cannabis use makes young brains more sensitive to the first exposure to cocaine, according to a new study on rodents led by scientists at Columbia University and the University of Cagliari in Italy. By monitoring the brains of both adolescent and adult rats after giving them synthetic psychoactive cannabinoids followed by cocaine, the research team identified key molecular and epigenetic changes that occurred in the brains of adolescents -- but not adults. This discovery reveals a new interplay between the two drugs that had never previously been directly observed in biological detail.

These findings, reported this week in the Proceedings of the National Academy of Sciences, provide new understanding of how the abuse of cannabis during teenage years may enhance the first experience with cocaine and lead to continued use among vulnerable individuals.

"We know from human epidemiological studies that individuals who abuse cocaine have a history of early cannabis use, and that a person's initial response to a drug can have a large impact on whether they continue to use it. But many questions remain on how early cannabis exposure affects the brain," said epidemiologist Denise Kandel, PhD, who is a professor of Sociomedical Sciences in Psychiatry at Columbia's Vagelos College of Physicians and Surgeons and co-senior author of today's paper.

"Our study in rats is the first to map the detailed molecular and epigenetic mechanisms by which cocaine interacts with brains already exposed to cannabinoids, providing much-needed clarity to the biological mechanisms that may increase the risk for drug abuse and addiction," added co-author and Nobel laureate Eric Kandel, MD, codirector of Columbia's Mortimer B. Zuckerman Mind Brain Behavior Institute and Senior Investigator of the Howard Hughes Medical Institute.

Previous research had revealed key differences in how cannabis and cocaine affect brain chemistry. "Studies on the addictive properties of cocaine have traditionally focused on the mesolimbic dopaminergic pathway, a brain system that underlies our motivation to pursue pleasurable experiences," said Philippe Melas, PhD, who was an associate research scientist in Eric Kandel's lab at Columbia's Zuckerman Institute and is the paper's co-senior author. "While cannabis enhances mesolimbic dopaminergic activity similarly to cocaine, it also affects an entirely different neurochemical system that is widespread in the brain called the endocannabinoid system. This system is essential for brain development -- a process that is still ongoing in adolescence."

Besides the dopaminergic system, both cannabis and cocaine appear to share some additional features. Recent studies have suggested that the development of cocaine craving is dependent on the brain's glutamatergic system. This system uses glutamate, a brain molecule that acts as a synaptic transmitter in the brain, enhancing the transmission of signals between the brain's neurons. According to previous research, as well as findings presented in today's new study, using cannabis during adolescence may also affect this glutamatergic signaling process.

To delve deeper into a potential link between the two drugs, Dr. Melas and the husband-and-wife team of Drs. Eric and Denise Kandel partnered with Paola Fadda, PhD, Maria Scherma, PhD, and Walter Fratta, PhD, researchers in the Department of Biomedical Sciences, at the University of Cagliari in Italy. The group examined the behavioral, molecular and epigenetic changes that occur when both adolescent and adult rats are first exposed to WIN, a synthetic cannabinoid with psychoactive properties similar to those of THC found in cannabis, and then are subsequently exposed to cocaine.

"We found that adolescent rats that had been pre-exposed to WIN had an enhanced reaction to their initial exposure to cocaine. Notably, we observed this effect in adolescent but not in adult rats," said Dr. Melas, who is now a junior researcher in the Department of Clinical Neuroscience at the Karolinska Institutet in Sweden.

Upon further examination, the team found that, when preceded by a history of psychoactive cannabinoid use in adolescence, exposure to cocaine sets off a battery of unique molecular reactions in the rat brain. These reactions included not only changes in the aforementioned glutamate receptors but also key epigenetic modifications. Epigenetic modifications are distinct, in that they affect the way genes are switched on or off but do not affect the sequence of the genes themselves.

The Columbia team had previously found similar epigenetic mechanisms in adult animals in response to nicotine and alcohol in the brain's reward center, known as the nucleus accumbens. In the present study, however, the epigenetic effects of cannabinoids were found to be specific to adolescents and to target the brain's prefrontal cortex. The prefrontal cortex, which plays a role in various executive functions, including long-term planning and self-control, is one of the last regions of the brain to reach maturity, a fact that has long been linked to adolescents' propensity for risky behavior.

Moreover, aberrant prefrontal cortex activity is often observed in patients suffering from addiction. Efforts to enhance the function of the prefrontal cortex are currently being evaluated in the treatment of addiction through the use of brain stimulation and other methodologies.

"Our findings suggest that exposure to psychoactive cannabinoids during adolescence primes the animals' prefrontal cortex, so that it responds differently to cocaine compared to animals who had been given cocaine without having previously experienced cannabis," said Dr. Melas.

These results in rats offer important clues to the biological mechanisms that may underlie the way that different classes of drugs can reinforce each other in humans. The results also support the notion that cannabis abuse during adolescence can enhance a person's initial positive experience with a different drug, such as cocaine, which in turn can have an effect on whether that person chooses to continue, or expand, their initial use of cocaine.

"This study suggests that teenagers who use cannabis may have a favorable initial reaction to cocaine, which will increase their likelihood of engaging in its repeated use so that they eventually become addicted, especially if they carry additional environmental or genetic vulnerabilities," said Dr. Denise Kandel.

Most research involving rodents and addiction has traditionally focused on adult animals. It has also largely been limited to studying one substance of abuse at a time, without taking into consideration a history of drug exposure in adolescence.

"These and other experiments are key to understanding the molecular changes to the brain that occur during drug use," said Dr. Eric Kandel, who is also University Professor and Kavli Professor of Brain Science at Columbia. "This knowledge will be crucial for developing effective treatments that curb addiction by targeting the disease's underlying mechanisms."

https://www.sciencedaily.com/releases/2020/04/200420165718.htm

Alzheimer's drug reverses brain damage from adolescent alcohol exposure in rats

Results offer clues to how adolescent binge drinking changes learning, memory in young adults

August 20, 2019

Science Daily/Duke University Medical Center

A drug used to slow cognitive decline in adults with Alzheimer's disease appears to reverse brain inflammation and neuron damage in rats exposed to alcohol during adolescence.

In a study described in the journal Scientific Reports, Duke Health researchers sought to understand how intermittent binge drinking changes the hippocampus -- a region long known to be critical for learning and memory, and also linked to anxiety -- and whether the drug, donepezil, could reverse those changes. Rats were used as a model for teens and young adults who binge drink a few times a week.

"Research has begun to show that human adolescents who drink early and consistently across the adolescent years have some deficits in brain function that can affect learning and memory, as well as anxiety and social behaviors," said senior author Scott Swartzwelder, Ph.D., professor of psychiatry at Duke.

"The changes can be subtle, but who wants even subtle deficits in their brain function or how they think and feel?" Swartzwelder said. "Studies in animal models show that adolescent alcohol exposure can change the ways nerve cells communicate with each other, and the level of plasticity in brain circuits -- compromising the ability of the brain to change and adapt. These changes can be seen in adulthood -- long after the alcohol exposure has ended"

Because they can't ethically have young people drink alcohol to study its effects, researchers use the developing brains of rats to understand the effects of "intermittent alcohol exposure," resulting in blood-alcohol levels that are consistent with those achieved by human adolescent drinkers.

The scientists observed that in addition to brain inflammation, adolescent alcohol exposure inhibited the birth of new neurons in the hippocampus, Swartzwelder said, and may even accelerate neuronal death -- making it is easier to lose existing cells and more difficult to produce new ones.

Once the rats reached adulthood, they were given donepezil, a cognition-enhancing drug that is marketed under the brand name Aricept. After four days of treatment, the researchers studied the animals' brains, looking closely at the hippocampus. The rats that received donepezil in adulthood after adolescent alcohol exposure showed less inflammation and better ability to produce new neurons compared to rats that did not receive the donepezil treatment.

"We don't know if the reversal of these alcohol effects by donepezil is permanent, but it at least transiently reverses them," Swartzwelder said.

Swartzwelder said the study helps clarify the subtle health risk of heavy drinking among young adults, which has been difficult to ascertain.

"It's obvious that not everyone who drinks during adolescence grows up and completely fails at life," Swartzwelder said. "You might not notice the deficits in obvious ways every day, but you run the risk of losing your edge. Sometimes a small impairment of brain function can have a broad ripple effect in someone's life."

Importantly, the research demonstrates the potential to repair some types of damage caused by adolescent alcohol exposure, he said. But beyond that, it could also lead to a more specific understanding of the cellular mechanisms that make the developing brain particularly vulnerable to substances such as alcohol.

The research was part of the Neurobiology of Adolescent Drinking in Adulthood (NADIA) Consortium and was supported by the National Institute on Alcohol Abuse and Alcoholism and the National Institutes of Health

https://www.sciencedaily.com/releases/2019/08/190820081840.htm

College students use more marijuana in states where it's legal, but they binge drink less

January 13, 2020

Science Daily/Oregon State University

Marijuana use among college students has been trending upward for years, but in states that have legalized recreational marijuana, use has jumped even higher.

An Oregon State University study published today in Addiction shows that in states where marijuana was legalized by 2018, both occasional and frequent use among college students has continued to rise beyond the first year of legalization, suggesting an ongoing trend rather than a brief period of experimentation.

Overall, students in states with legal marijuana were 18% more likely to have used marijuana in the past 30 days than students in states that had not legalized the drug. They were also 17% more likely to have engaged in frequent use, defined as using marijuana on at least 20 of the past 30 days.

The differences between states with and without legalization escalated over time: Six years after legalization in early-adopting states, students were 46% more likely to have used marijuana than their peers in non-legalized states.

Between 2012 and 2018, overall usage rates increased from 14% to 17% in non-legalized states, but shot up from 21% to 34% in the earliest states to legalize the drug. Similar trends appeared in states that legalized marijuana more recently.

Conducted by Harold Bae from OSU's College of Public Health and Human Sciences and David Kerr from OSU's College of Liberal Arts, this is the first study of college students to look broadly at multiple states that have legalized recreational marijuana and to go beyond the first year following legalization.

It includes data from seven states and 135 colleges where marijuana was legalized by 2018 and from 41 states and 454 colleges where recreational use was not legal.

That scope allowed Bae and Kerr to examine trends in the earliest adopting states as well as more recent adopters -- though, the data for the study is stripped of state- and college-identifying information, so does not speak specifically to any one state or institution.

The data comes from the National College Health Assessment survey from 2008 to 2018, which asks about a wide range of health behaviors including drug and alcohol use and is administered anonymously to encourage students to respond more honestly. More than 850,000 students participated.

Looking at specific demographics, researchers found that the effect was stronger among older students ages 21-26 than minors ages 18-20; older students were 23% more likely to report having used marijuana than their peers in non-legalized states. The effect was also stronger among female students and among students living in off-campus housing, possibly because universities adhere to federal drug laws that still classify marijuana as an illegal substance.

"It's easy to look at the findings and think, 'Yeah, of course rates would increase,'" Kerr said. "But we need to quantify the effects these policy changes are having."

Furthermore, he said, researchers are not finding increases in adolescents' marijuana use following legalization. "So it is surprising and important that these young adults are sensitive to this law. And it's not explained by legal age, because minors changed too."

A recent companion study published in Addictive Behaviors in November by OSU doctoral candidate Zoe Alley along with Kerr and Bae examined the relationship between recreational marijuana legalization and college students' use of other substances.

Using the same dataset, they found that after legalization, students ages 21 and older showed a greater drop in binge drinking than their peers in states where marijuana was not legal. Binge drinking was defined as having five or more drinks in a single sitting within the previous two weeks.

Researchers have not yet tested any hypotheses as to why binge drinking fell, but they have some ideas.

An outside study previously found that illegal marijuana use decreases sharply when people hit 21 -- where there is a sharp increase in alcohol use.

"When you're under 21, all substances are equally illegal," Alley said. "In most states, once you reach 21, a barrier that was in the way of using alcohol is gone, while it's intact for marijuana use. But when marijuana is legal, this dynamic is changed."

Binge drinking has been on the decline among college students in recent years, but dropped more in states that legalized marijuana than in states that did not.

"So in these two studies we saw changes after legalization that really differed by substance," Kerr said. "For marijuana we saw state-specific increases that went beyond the nationwide increases, whereas binge drinking was the opposite: a greater decrease in the context of nationwide decreases."

The magnitude of effect was much larger with marijuana than with any of the other substances, Bae added. "So the changes following recreational marijuana legalization were quite specific to cannabis use."

Future research is needed to see how those trends hold up over time, as additional states legalize marijuana and existing states continue to tweak their current policies, the researchers said.

https://www.sciencedaily.com/releases/2020/01/200113131637.htm