Early-and-regular cannabis use by youth is associated with alteration in brain circuits that support cognitive control
June 20, 2019
Science Daily/Elsevier
The development of neural circuits in youth, at a particularly important time in their lives, can be heavily influenced by external factors -- specifically the frequent and regular use of cannabis. A new study in the Journal of the American Academy of Child and Adolescent Psychiatry (JAACAP), published by Elsevier, reports that alterations in cognitive control -- an ensemble of processes by which the mind governs, regulates and guides behaviors, impulses, and decision-making based on goals are directly affected.
The researchers found that these brain alterations were less intense in individuals who recently stopped using cannabis, which may suggest that the effects of cannabis are more robust in recent users. Additional findings from the study also suggest greater and more persistent alterations in individuals who initiated cannabis use earlier, while the brain is still developing.
"Most adults with problematic substance use now were most likely having problems with drugs and alcohol in adolescence, a developmental period during which the neural circuits underlying cognitive control processes continue to mature," said lead author Marilyn Cyr, PhD. "As such, the adolescent brain may be particularly vulnerable to the effects of substance use, particularly cannabis -- the most commonly used recreational drug by teenagers worldwide," added the postdoctoral scientist in the Division of Child and Adolescent Psychiatry at the New York State Psychiatric Institute, Vagelos College of Physicians & Surgeons, Columbia University, New York.
The findings are based on functional magnetic resonance imaging (fMRI) data acquired from 28 adolescents and young adults (aged 14-23 years) with significant cannabis use and 32 age and sex-matched non-using healthy controls. Participants were scanned during their performance of a Simon Spatial Incompatibility Task, a cognitive control task that requires resolving cognitive conflict to respond accurately.
Compared to their healthy counterparts, the adolescents and young adults with significant cannabis use showed reduced activation in the frontostriatal circuits that support cognitive control and conflict resolution.
The authors also examined the degree to which fluctuations in activity in relation to conflict resolution is synchronized across the different regions comprised in this frontostriatal circuit (that is, to what extent are regions functionally connected with each other). Although circuit connectivity did not differ between cannabis-using and non-using youth, the research team found an association between how early individuals began regularly using cannabis and the extent to which frontostriatal regions were disrupted, suggesting that earlier chronic use may have a larger impact on circuit development than use of later onset.
"The present findings support the mission of the Adolescent Brain and Cognitive Development study, a longitudinal study aimed at understanding the developmental trajectory of brain circuits in relation to cannabis use," said Dr. Cyr. "In addition, these findings are a first step towards identifying brain-based targets for early interventions that reduce addiction behaviors by enhancing self-regulatory capacity.
"Given that substance use and relapse rates are associated with control processes, interventions based on neural stimulation, such as transcranial magnetic stimulation (TMS), and behavioral interventions, such as cognitive training, that specifically target the brain circuits underlying these control processes may be helpful as adjunct intervention strategies to complement standard treatment programs for cannabis use disorder."
https://www.sciencedaily.com/releases/2019/06/190620104858.htm
Early use of marijuana can increase its negative health impacts
A study cautions of risks for young consumers
March 28, 2017
Science Daily/Concordia University
With new legislation imminent in Canada, marijuana is a hot topic these days. Those who smoke it may be cheering. Those who've never tried it may be thinking, why not? And those looking to make a business out of it are grappling with how to navigate a challenging product.
But one of the most contentious aspects of legalization is age. A report by the Canadian Task Force on Cannabis Legalization and Regulation, released in December 2016, recommends marijuana use be restricted to those 18 years old and older.
The need for age guidelines falls in line with a new study by James McIntosh, professor of economics in the Faculty of Arts and Science. Recently published in the journal Health, the findings show that young users report the most impact to their physical and mental health.
The article also shows that those who wait until the age of 21 to use the drug are unlikely to develop a lifelong habit.
Heightened risks for youth
For the study, McIntosh and his co-author Rawan Hassunah (BA 16) examined the results of three national surveys on tobacco, alcohol and drug use -- two in Canada and one in the United States.
"We wanted to see what the effects of regular marijuana use were on self-reported physical and mental health," McIntosh explains.
The report cites other studies demonstrating the negative impacts of marijuana. It's the first, however, to look so closely at age of first use.
In terms of overall effects, the study confirmed that marijuana does affect people's physical and mental health, that it will cause cognitive impairment, memory loss, diminished IQ, limited educational success and likelihood for developing mental illness. Physically, early users also suffer higher rates of respiratory diseases and certain cancers.
McIntosh says the younger you start, the worse the impacts.
"We found that if age of first use is below 15, it's always bad for you."
The argument for legalization
So how can these findings translate into informing youth about the risks? Besides legislation, McIntosh recommends educational programs, counselling services and a distribution system that minimizes use by young people.
Despite his warnings about age restrictions, however, he says legalization will bring more good than harm.
"The task force outlines these benefits -- to take marijuana out of criminal hands, to tax it, to make sure that product quality is preserved."
McIntosh adds that being at the cusp of legalization puts Canada in a unique position to begin rigorous study of cannabis and its effects.
"We need to start collecting data on it to see what the effects are on people of all ages. You can get all kinds of information on drinking behaviours -- they should do that with marijuana."
https://www.sciencedaily.com/releases/2017/03/170328105901.htm
Marijuana and vulnerability to psychosis
July 5, 2017
Science Daily/University of Montreal
The link between marijuana use and psychotic-like experiences has been confirmed in a Canadian adolescent cohort.
Going from an occasional user of marijuana to a weekly or daily user increases an adolescent's risk of having recurrent psychotic-like experiences by 159%, according to a new Canadian study published in the Journal of Child Psychology and Psychiatry. The study also reports effects of marijuana use on cognitive development and shows that the link between marijuana use and psychotic-like experiences is best explained by emerging symptoms of depression.
"To clearly understand the impact of these results, it is essential to first define what psychotic-like experiences are: namely, experiences of perceptual aberration, ideas with unusual content and feelings of persecution," said the study's lead author, Josiane Bourque, a doctoral student at Université de Montréal's Department of Psychiatry. "Although they may be infrequent and thus not problematic for the adolescent, when these experiences are reported continuously, year after year, then there's an increased risk of a first psychotic episode or another psychiatric condition."
She added: "Our findings confirm that becoming a more regular marijuana user during adolescence is, indeed, associated with a risk of psychotic symptoms. This is a major public-health concern for Canada."
What are the underlying mechanisms?
One of the study's objectives was to better understand the mechanisms by which marijuana use is associated with psychotic-like experiences. Bourque and her supervisor, Dr. Patricia Conrod at Sainte Justine University Hospital Research Centre hypothesized that impairments in cognitive development due to marijuana misuse might in turn exacerbate psychotic-like experiences.
This hypothesis was only partially confirmed, however. Among the different cognitive abilities evaluated, the development of inhibitory control was the only cognitive function negatively affected by an increase in marijuana use. Inhibitory control is the capacity to withhold or inhibit automatic behaviours in favor of a more contextually appropriate behaviour. Dr. Conrod's team has shown that this specific cognitive function is associated with risk for other forms of substance abuse and addiction.
"Our results show that while marijuana use is associated with a number of cognitive and mental health symptoms, only an increase in symptoms of depression -- such as negative thoughts and low mood -- could explain the relationship between marijuana use and increasing psychotic-like experiences in youth," Bourque said.
What's next
These findings have important clinical implications for prevention programs in youth who report having persistent psychotic-like experiences. "While preventing adolescent marijuana use should be the aim of all drug strategies, targeted prevention approaches are particularly needed to delay and prevent marijuana use in young people at risk of psychosis," said Patricia Conrod, the study's senior author and a professor at UdeM's Department of Psychiatry.
Conrod is optimistic about one thing, however: the school-based prevention program that she developed, Preventure, has proven effective in reducing adolescent marijuana use by an overall 33%. "In future programs, it will be important to investigate whether this program and other similar targeted prevention programs can delay or prevent marijuana use in youth who suffer from psychotic-like experiences," she said. "While the approach seems promising, we have yet to demonstrate that drug prevention can prevent some cases of psychosis."
A large youth cohort from Montreal
The study's results are based on the CIHR-funded Co-Venture project, a cohort of approximately 4,000 adolescents aged 13 years old from 31 high schools in the Greater Montreal area. These teens are followed annually from Grade 7 to Grade 11. Every year they fill out computerized questionnaires to assess substance use and psychiatric symptoms. The teens also complete cognitive tasks to allow the researchers to evaluate their IQ, working memory and long-term memory as well as their inhibitory control skills.
To do their study, the research team first confirmed results from both the United Kingdom and Netherlands showing the presence of a small group of individuals (in Montreal, 8%) among the general population of adolescents who report recurrent psychotic-like experiences. Second, the researchers explored how marijuana use between 13 and 16 years of age increases the likelihood of belonging to the 8%. Finally, they examined whether the relationship between increasing use of marijuana and increasing psychotic-like experiences can be explained by emerging symptoms of anxiety or depression, or by the effects of substance use on developing cognitive abilities.
https://www.sciencedaily.com/releases/2017/07/170705104042.htm