How cannabis use during adolescence affects brain regions associated with schizophrenia
May 8, 2012
Science Daily/Royal College of Surgeons in Ireland (RCSI)
New research from the Royal College of Surgeons in Ireland (RCSI) published in Nature's Neuropsychopharmacology has shown physical changes to exist in specific brain areas implicated in schizophrenia following the use of cannabis during adolescence. The research has shown how cannabis use during adolescence can interact with a gene, called the COMT gene, to cause physical changes in the brain.
The COMT gene provides instructions for making enzymes which breakdown a specific chemical messenger called dopamine. Dopamine is a neurotransmitter that helps conduct signals from one nerve cell to another, particularly in the brains reward and pleasure centres. Adolescent cannabis use and its interaction with particular forms of the COMT gene have been shown to cause physical changes in the brain as well as increasing the risk of developing schizophrenia.
Dr Áine Behan, Department of Physiology, RCSI and lead author on the study said 'This is the first study to show that the combined effects of the COMT gene with adolescent cannabis use cause physical changes in the brain regions associated with schizophrenia. It demonstrates how genetic, developmental and environmental factors interact to modulate brain function in schizophrenia and supports previous behavioural research which has shown the COMT gene to influence the effects of adolescent cannabis use on schizophrenia-related behaviours.
The three areas of the brain assessed in this study were found to show changes in cell size, density and protein levels.
'Increased knowledge on the effects of cannabis on the brain is critical to understanding youth mental health both in terms of psychological and psychiatric well-being,' Dr Behan continued.
The research was funded by the Health Research Board and Science Foundation Ireland.
Senior authors include Professor David Cotter and Professor Mary Cannon, Department of Psychiatry and Professor John Waddington, Department of Molecular and Cellular Therapeutics, RCSI. Additional authors in the study included Magdalena Hryniewiecka,
Department of Psychiatry, RCSI, Dr Colm O'Tuathaigh and Dr Anthony Kinsella, Department of Molecular and Cellular Therapeutics, RCSI as well as collaborators Professor Maria Karayiorgou and Professor Joseph Gogos from the Department of Neuroscience, Columbia University, New York.
https://www.sciencedaily.com/releases/2012/05/120508112748.htm
Surge in cannabis use among youth preceded legalization in Canada
March 25, 2019
Science Daily/University of Waterloo
National discussions on cannabis legalization, along with increased access to medical marijuana, may have encouraged more high school students to consume the drug years before it became legal in Canada.
A recent study using data from more than 230,000 questionnaires by Canadian high school students in grades 9 to 12 found that almost 10 per cent reported having used the drug at least once per week in 2017-18, with a further 18 per cent saying they had used it at least once in the last year.
Both weekly and occasional use reached their lowest points in 2014-15 (9 percent and 15 percent respectively) and have since been rising steadily.
"The problem was developing while legalization was being discussed, but well before concrete steps to change the law were taken," said lead author Alex Zuckermann, a post-doctoral fellow with the Public Health Agency of Canada working in the School of Public Health and Health Systems.
"With medicinal use more widespread and talk of total legalization starting, we saw a shift in public perception starting around 2014. Before that, youth cannabis use was declining. These changing social norms may have contributed to rising youth use."
The work used data from the COMPASS Study, an annual survey of high school students in grades 9 to 12 in Ontario and Alberta. The demographic groups that saw the biggest increases since 2014-15 were female and Indigenous youth. Weekly use for females went from 7 to 8 percent, and occasional use from 17 to 19 percent during this time period. Indigenous youth weekly use went from 23 to 25 percent, and occasional use from 18 to 21 percent.
"We often think of male youth when we talk about drug use, but here female students are driving increases. Historically, their use has been more stigmatized, so normalization may be having a bigger effect," said Zuckermann. "We also see that Indigenous youth start young and have by far the highest rates of current use, factors that will have long-term health implications and need to be addressed."
In 2017-18, rates of lifetime and past-year cannabis use were highest among male (33 and 29 percent) and Indigenous students (55 and 46 percent), and lowest among Asian students (17 and 14 percent). Female students stood at 31 percent for lifetime use and 26 percent in the past year.
"The ability to track multiple risk factors among youth over time and maintain ongoing data systems like COMPASS can provide valuable information to policymakers," added Scott Leatherdale, principal investigator and a professor in the School of Public Health and Health Systems. "It helps to provide the necessary evidence to learn from new policy implementation."
https://www.sciencedaily.com/releases/2019/03/190325120358.htm
Cannabis: It matters how young you start
May 18, 2018
Science Daily/University of Montreal
Researchers find that boys who start smoking pot before 15 are much more likely to have a drug problem at 28 than those who start at 15 or after.
What a difference a year or two can make: If you started smoking marijuana at the start of your teens, your risk of having a drug abuse problem by age 28 is 68 per cent, but if you started smoking between 15 and 17 your risk drops to 44 per cent, according to a new study by Université de Montréal researchers.
All the more reason, they say, to educate kids early, in primary school, about the risks of starting pot smoking, especially now that the potency is much greater than it was in decades past and that public acceptance is being spurred by legalization in jurisdictions such as Canada.
"The odds of developing any drug abuse symptoms by age 28 were reduced by 31 per cent for each year of delayed onset of cannabis use in adolescence," the researchers at UdeM's Department of Psychology, School of Psychoeducation and the CHU Saint-Justine Hospital Research Centre found.
Their study was published April 22 in the Canadian Journal of Psychiatry.
Percentage nearly tripled
According to a 2011 study by University of Waterloo researchers in the journal Addictive Behaviors, 10 per cent of Canadian adolescents consumed cannabis in Grade 8. By Grade 12, that percentage nearly tripled to 29 per cent. Early-onset cannabis use has been linked to further drug abuse problems later in life.
The new study, done by UdM doctoral student Charlie Rioux under the supervision of professors Natalie Castellanos-Ryan and Jean Séguin, shows just how much.
The researchers looked at data for 1,030 boys in the Montreal Longitudinal and Experimental Study of white francophones from some of the city's impoverished neighbourhoods begun in the early 1980s. Every year between ages 13 and 17, the boys were asked if they had consumed cannabis at all in the previous year.
At 17, and again at 20 and 28, they were asked not only whether they consumed cannabis, but also other drugs, including hallucinogens, cocaine, amphetamines, barbiturates, tranquilizers, heroin and inhalants. Then the data were correlated with the age at which they started using cannabis.
Double the chance if frequent use
The results confirmed the researchers' suspicions: the younger they started, the more likely the boys had a drug problem later as young men. This is partly explained by the frequency with which they consumed cannabis and other drugs, but those who started before age 15 were at higher risk regardless of how often they consumed.
"The odds of developing any drug abuse symptoms by age 28 were non-significant if cannabis use had its onset at ages 15 to 17, but were significant and almost doubled each year if onset was before age 15," the study says. Even if those who start smoking cannabis at 17 years were at lower risk, frequent users (20 or more times a year) at age 17 had almost double the chance of abuse by age 28 than occasional users.
And that may be underestimating the problem, the researchers say.
"Notably, considering that the potency of cannabis products increased over the last two decades and that [inthis study] adolescent cannabis use was assessed from 1991 to 1995, it is possible that the higher content of ?-9-tetrahydrocannabinol in the cannabis available today would be associated with higher rates of drug abuse symptoms."
Gangs, thievery, drinking
The researchers also found that the earlier that boys were involved in gangs, drank alcohol, got into fights, stole or vandalized property, the earlier they used cannabis and the higher their odds of having drug abuse issues by 28. Those who started drinking at 17 also were at higher risk of having an alcohol problem at 28.
The finding that starting pot smoking between ages 13 and 15 increases the odds of developing a drug problem later on makes it all the more important to prevent or reducing cannabis use as early as possible, the researchers say.
"It may be important to implement these programs by the end of elementary school to prevent early onset of cannabis use," said Rioux. "Since peer influence and delinquency were identified as early risk factors for earlier cannabis onset and adult drug abuse, targeting these risk factors in prevention programs may be important, especially since prevention strategies working on the motivators of substance use have been shown to be effective."
https://www.sciencedaily.com/releases/2018/05/180518102757.htm