Cannabis damages young brains more than originally thought

December 20, 2009

Science Daily/McGill University Health Centre

Canadian teenagers are among the largest consumers of cannabis worldwide. The damaging effects of this illicit drug on young brains are worse than originally thought, according to new research by Dr. Gabriella Gobbi, a psychiatric researcher from the Research Institute of the McGill University Health Centre. The new study, published in Neurobiology of Disease, suggests that daily consumption of cannabis in teens can cause depression and anxiety, and have an irreversible long-term effect on the brain.

"We wanted to know what happens in the brains of teenagers when they use cannabis and whether they are more susceptible to its neurological effects than adults," explained Dr. Gobbi, who is also a professor at McGill University. Her study points to an apparent action of cannabis on two important compounds in the brain -- serotonin and norepinephrine -- which are involved in the regulation of neurological functions such as mood control and anxiety.

"Teenagers who are exposed to cannabis have decreased serotonin transmission, which leads to mood disorders, as well as increased norepinephrine transmission, which leads to greater long-term susceptibility to stress," Dr. Gobbi stated.

Previous epidemiological studies have shown how cannabis consumption can affect behaviour in some teenagers. "Our study is one of the first to focus on the neurobiological mechanisms at the root of this influence of cannabis on depression and anxiety in adolescents," confirmed Dr. Gobbi. It is also the first study to demonstrate that cannabis consumption causes more serious damage during adolescence than adulthood.

Dr. Gabriella Gobbi is a researcher at the neuroscience axis of the Research Institute of the McGill University Health Centre and also a psychiatrist and associate professor at the Department of Psychiatry, McGill University.

This study was funded by a grant from The Canadian Psychiatric Research Foundation (CPRF)

https://www.sciencedaily.com/releases/2009/12/091217115834.htm

Heavy Marijuana Use May Damage Developing Brain in Teens, Young Adults

February 3, 2009

Science Daily/Children's Hospital of Philadelphia

Adolescents and young adults who are heavy users of marijuana are more likely than non-users to have disrupted brain development, according to a new study. Pediatric researchers found abnormalities in areas of the brain that interconnect brain regions involved in memory, attention, decision-making, language and executive functioning skills. The findings are of particular concern because adolescence is a crucial period for brain development and maturation.

The researchers caution that the study is preliminary and does not demonstrate that marijuana use causes the brain abnormalities. However, "Studies of normal brain development reveal critical areas of the brain that develop during late adolescence, and our study shows that heavy cannabis use is associated with damage in those brain regions," said study leader Manzar Ashtari, Ph.D., director of the Diffusion Image Analysis and Brain Morphometry Laboratory in the Radiology Department of The Children's Hospital of Philadelphia.

The study appeared early last month in the Journal of Psychiatric Research. The current research builds on previous work by Ashtari and colleagues, who used the same imaging technology to analyze normal brain development in adolescent subjects.

In the current study, working with child psychiatrist Sanjiv Kumra, M.D., now at the University of Minnesota, Ashtari and colleagues performed imaging studies on 14 young men from a residential drug treatment center in New York State, as well as 14 age-matched healthy controls. All the study subjects were males, with an average age of 19. The researchers performed the imaging studies at Long Island Jewish Medical Center.

The 14 subjects from the drug treatment center all had a history of heavy cannabis use during adolescence. On average, they had smoked marijuana from age 13 till age 18 or 19, and reported smoking nearly 6 marijuana joints daily in the final year before they stopped using the drug.

The study team performed a type of magnetic resonance imaging scan called diffusion tensor imaging (DTI) that measures water movement through brain tissues. "The abnormal patterns of water diffusion that we found among the young men with histories of marijuana use suggest damage or an arrest in development of the myelin sheath that surrounds brain cells," said Ashtari. Myelin provides a coating around brain cells similar to insulation covering an electrical wire. If myelin does not function properly, signaling within the brain may be slower.

Myelin gives its color to the white matter of the brain, and covers the nerve fibers that connect different brain regions. "Our results suggest that early-onset substance use may alter the development of white matter circuits, especially those connections among the frontal, parietal and temporal regions of the brain," said Ashtari. "Abnormal white matter development could slow information transfer in the brain and affect cognitive functions."

Ashtari added that the findings are preliminary. Among other limitations of the study, such as a small sample size, five of the 14 subjects with heavy cannabis use also had a history of alcohol abuse, which may have contributed an effect. Also, it is possible that the brain abnormalities may have predisposed the subjects to drug dependence, rather than drug usage causing the brain abnormalities.

"Further research should be done to investigate the relation between repeated marijuana use and white matter development," said Ashtari. "However, our work reinforces the idea that the adolescent brain may be especially vulnerable to risky behaviors such as substance abuse, because of crucial neural development that occurs during those years."

The National Institute of Mental Health provided grant support for this research. Ashtari's and Kumra's co-authors were Kelly Cervellione, of Jamaica Hospital Medical Center, Jamaica, N.Y.; John Cottone, of Zucker Hillside Hospital, Glen Oaks, N.Y.; and Babak A. Ardekani, of The Nathan Kline Institute for Psychiatric Research, Orangeburg, N.Y. Serge Sevy of Zucker Hillside Hospital also contributed to the project.

https://www.sciencedaily.com/releases/2009/02/090202175105.htm

Teen 'Self Medication' for Depression Leads to More Serious Mental Illness

May 10, 2008

Science Daily/US National Drug Control Policy

Millions of American teens report experiencing weeks of hopelessness and loss of interest in normal daily activities and many of these depressed teens are using marijuana and other drugs, making their situation worse, according to a new White House report released today. The report, from the White House Office of National Drug Control Policy (ONDCP), reveals that marijuana use can worsen depression and lead to more serious mental disorders, such as schizophrenia, anxiety, and even suicide.

Research shows that some teens are using drugs to alleviate feelings of depression ("self-medicating"), when in fact, using marijuana can compound the problem. The report, released to coincide with May's Mental Health Awareness Month, shows a staggering two million teens felt depressed at some point during the past year, and depressed teens are more than twice as likely as non-depressed teens to have used marijuana during that same period. Depressed teens are also almost twice as likely to have used illicit drugs as non-depressed teens. They are also more than twice as likely as their peers to abuse or become dependent on marijuana. Marijuana use is associated with depression, suicidal thoughts, and suicide attempts.

"Marijuana is not the answer. Too many young people are making a bad situation worse by using marijuana in a misguided effort to relieve their symptoms of depression," said John P. Walters, Director, National Drug Control Policy. "Parents must not dismiss teen moodiness as a passing phase. Look closely at your teen's behavior because it could be a sign of something more serious."

Although marijuana use among teens has dropped by 25 percent since 2001, more teens use marijuana than all other illicit drugs combined. The new report, "Teen Marijuana Use Worsens Depression: An Analysis of Recent Data Shows 'Self-Medicating' Could Actually Make Things Worse," shows the following:

·     Teens who smoke marijuana at least once a month are three times more likely to have suicidal thoughts than non-users;

·     Using marijuana can cause depression and other mental illnesses;

·     The percentage of depressed teens is equal to the percentage of depressed adults, but depressed teens are more likely than depressed adults to use marijuana and other illicit drugs;

·     Teen girls who use marijuana daily are more likely to develop depression than girls who do not use marijuana;

·     Depressed teens are also more likely than non-depressed teens to engage in other risky behaviors such as daily cigarette use and heavy alcohol use.

·     "Don't be fooled into thinking that pot is harmless," said Dr. Drew Pinksy, internist, addiction expert, and host of VH1's Celebrity Rehab. "Marijuana is an addictive drug. Teens who are already depressed and use marijuana may increase their odds of suffering from even more serious mental health problems."

In fact, the potency of smoked marijuana has risen consistently over the past decades and higher potency translates into serious health consequences for teens. Some studies show that higher potency marijuana may be contributing to an increase in the number of American teens seeking treatment for marijuana dependence. The risks associated with recent and long-term marijuana use include schizophrenia, other forms of psychosis, and even suicide. "Not only are adolescents at greater risk for drug abuse, but they may suffer more consequences," said Nora D. Volkow, M. D., Director of the National Institute on Drug Abuse. "There is also some evidence that in vulnerable teens-because of genetic factors-the abuse of marijuana can trigger a schizophreniform disorder."

ONDCP is urging parents to pay closer attention to their teen's behavior and mood swings, and recognize that marijuana and other drugs could be playing a dangerous role in their child's life. Parents can take some concrete steps to protect their teen from marijuana and other illicit drug use:

·     Look closer at your teen's behavior-moodiness may not just be a passing phase; it could be sign of depression or drug use;

·     Recognize the warning signs of drug use and depression, including carelessness with grooming, change in behavior and friends, loss of interest in daily activities, and withdrawal from family;

·     Be more involved: monitor your teen's activities; ask questions and know how he or she spends time; set limits about drug use with clear rules and consequences for breaking them.

https://www.sciencedaily.com/releases/2008/05/080509105348.htm

Cannabis use in teens linked to risk of depression in young adults

Cannabis use among adolescents is found to be associated with increased risk of depression and anxiety in adulthood

February 13, 2019

Science Daily/University of Oxford

Cannabis is the most commonly used recreational drug by teenagers worldwide. In Canada, among youth aged 15 to 19 years, the rate of past-year cannabis use is 20.6 percent, while in England, 4 percent of adolescents aged 11 to 15 years used cannabis in the last month.

While there has been a lot of focus on the role of cannabis use in psychosis, there has been less attention on whether cannabis use is associated with an increased risk of common mental health disorders, such as depression and anxiety.

Researchers from McGill University and the University of Oxford carried out a systematic review and meta-analysis of the best existing evidence and analysed 23,317 individuals (from 11 international studies) to see whether use of cannabis in young people is associated with depression, anxiety and suicidality in early adulthood.

They found that cannabis use among adolescents is associated with a significant increased risk of depression and suicidality in adulthood (not anxiety). While the individual-level risk was found to be modest, the widespread use of the drug by young people makes the scale of the risk much more serious.

The population attributable risk was found to be around 7%, which translates to more than 400,000 adolescent cases of depression potentially attributable to cannabis exposure in the US, 25,000 in Canada and about 60,000 in the UK.

Dr. Gabriella Gobbi, Professor, Department of Psychiatry, McGill University and a scientist at the Research Institute of the McGill University Health Centre, states: "While the link between cannabis and mood regulation has been largely studied in preclinical studies, there was still a gap in clinical studies regarding the systematic evaluation of the link between adolescent cannabis consumption and the risk of depression and suicidal behaviour in young adulthood. This study aimed to fill this gap, helping mental health professionals and parents to better address this problem."

Professor Andrea Cipriani, NIHR Research Professor of Psychiatry at the University of Oxford, said: 'We looked at the effects of cannabis because its use among young people is so common, but the long-term effects are still poorly understood. We carefully selected the best studies carried out since 1993 and included only the methodologically sound ones to rule out important confounding factors, such us premorbid depression.'

'Our findings about depression and suicidality are very relevant for clinical practice and public health. Although the size of the negative effects of cannabis can vary between individual adolescents and it is not possible to predict the exact risk for each teenager, the widespread use of cannabis among the young generations makes it an important public health issue.

'Regular use during adolescence is associated with lower achievement at school, addiction, psychosis and neuropsychological decline, increased risk of motor vehicle crashes, as well as the respiratory problems that are associated with smoking.'

The active ingredient in cannabis,THC, mediates most of psychoactive and mood-related effects of cannabis and also has addictive properties. Preclinical studies in laboratory animals reported an association between pubertal exposure to cannabinoids and adult-onset depressive symptoms. It is thought that cannabis may alter the physiological neurodevelopment (frontal cortex and limbic system) of adolescent brains.

While the review of observational studies was the first to look at the effects of cannabis use in adolescents only, it was not possible to predict the risk at the individual level, nor was it possible to discern information about the dose-dependent risk of cannabis use.

https://www.sciencedaily.com/releases/2019/02/190213172307.htm