Cannabis use among adolescents is not without risk for cognitive development

Although studies have shown that alcohol and cannabis abuse are related to cognitive impairment in youth, no previous studies have been designed to understand this relationship and to differentiate between cannabis use as a cause or a consequence of cognitive impairment. A new study by researchers at CHU Sainte-Justine and the Université de Montréal, published in the American Journal of Psychiatry, shows that beyond the role of cognition in vulnerability to substance use, the simultaneous and long-lasting effects of cannabis use in adolescents can be observed on important cognitive functions and appear to be more pronounced than those observed for alcohol.

Beyond acute intoxicants, alcohol and cannabis abuse has been associated with learning, memory, attention and decision-making disorders, as well as academic achievement. inferior. "Although many studies have found differences in cognitive performance between youth user and non-user groups, the causal and long-lasting effects of substance use on adolescent cognitive development still needed to be established," he said. the co-author. student at the University of Montreal, Jean-François G. Morin. Patricia Conrod, senior author and researcher at the Department of Psychiatry at the University of Montreal, added that "very few studies are designed to examine this issue from a development perspective. that it follows a large sample of students in Grades 7 to 10 with the help of cognitive measures and substance use, and with this large-data-based approach we have been able to model the nature of complex of the relationship between these sets of variables. "

To understand the relationship between alcohol, cannabis use and cognitive development in adolescents at all levels of consumption (abstinence, occasional consumption or high consumption), the research team followed a sample of 3,826 Canadian teens over a four-year period. Using a development-sensitive design, the authors investigated the relationships between annual changes in substance use and cognitive development in a number of cognitive domains, such as recall memory, perceptual reasoning, inhibition and working memory. Multilevel regression models were used to simultaneously test for vulnerability and the simultaneous and lasting effects on each cognitive domain. The study found that vulnerability to cannabis and alcohol consumption in adolescence was associated with generally lower performance across all cognitive domains.

"However, a further increase in cannabis use, but not alcohol consumption, has shown additional simultaneous and delayed effects on cognitive functions, such as perceptual reasoning, recall of memory, memory of work and inhibitory control, "said Conrod. "The finding that cannabis use was associated with lasting effects on a measure of inhibitory control, a risk factor for other addictive behaviors, could explain why early cannabis use is a risk factor for alcohol use. other addictions. " Morin added, "Some of these effects are even more pronounced when consumption begins earlier in adolescence."

In a context where policies and attitudes regarding substance use are being reconsidered, this research underscores the importance of protecting young people from the harmful effects of consumption by investing more in substance abuse programs. drug prevention.

"It will be important to conduct similar analyzes with this cohort or with similar cohorts as they transition to early adulthood, when alcohol and cannabis use becomes more severe," Conrod said. "This could be particularly relevant for the effects of alcohol: although this study did not detect the effects of alcohol consumption in adolescents on cognitive development, the neurotoxic effects may be observed in specific subgroups differentiated by level of consumption, sex or age. " Morin added: "We also want to determine if these effects on brain development are related to other difficulties such as poor school performance, neuroanatomical damage and the risk of future addiction or mental health disorders."

The article entitled "A population analysis of the relationship between substance use and cognitive development of adolescents" was published in the American Journal of Psychiatry in October 2018.

Explore further:
Scientists identify 35 genes associated with cannabis use