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 cannabis use is not without risk to cognitive development
October 3, 2018
Science Daily/Université de Montréal
A new study confirms that cannabis use is related to impaired and lasting effects on adolescent cognitive development.
Although studies have shown that alcohol and cannabis misuse are related to impaired cognition in youth, previous studies were not designed to understand this relationship and differentiate whether cannabis use was causal or consequential to cognitive impairment. A new study by researchers at CHU Sainte-Justine and Université de Montréal, published in the American Journal of Psychiatry, shows that beyond the role of cognition in vulnerability to substance use, the concurrent and lasting effects of adolescent cannabis use can be observed on important cognitive functions and appear to be more pronounced than those observed for alcohol.
Beyond acute intoxicating effects, alcohol and cannabis misuse has been associated with impairments in learning, memory, attention and decision-making, as well as with lower academic performance. "While many studies have reported group differences in cognitive performance between young users and non-users, what had yet to be established was the causal and lasting effects of teen substance use on cognitive development," said co-author and PhD student at Université de Montréal, Jean-François G. Morin. Senior author and investigator Dr. Patricia Conrod, from the Department of Psychiatry at Université de Montréal, added that "very few studies are designed to look at this question from a developmental perspective. Our study is unique in that it followed a large sample of high school students from 7th to 10th grade using cognitive and substance-use measures. Using this big-data approach, we were able to model the complex nature of the relationship between these sets of variables."
To understand the relationship between alcohol, cannabis use and cognitive development among adolescents at all levels of consumption (abstinent, occasional consumer or high consumer), the research team followed a sample of 3,826 Canadian adolescents over a period of four years. Using a developmentally sensitive design, the authors investigated relationships between year-to-year changes in substance use and cognitive development across a number of cognitive domains, such as recall memory, perceptual reasoning, inhibition and working memory. Multi-level regression models were used to simultaneously test vulnerability and concurrent and lasting effects on each cognitive domain. The study found that vulnerability to cannabis and alcohol use in adolescence was associated with generally lower performance on all cognitive domains.
"However, further increases in cannabis use, but not alcohol consumption, showed additional concurrent and lagged effects on cognitive functions, such as perceptual reasoning, memory recall, working memory and inhibitory control," Conrod said. "Of particular concern was the finding that cannabis use was associated with lasting effects on a measure of inhibitory control, which is a risk factor for other addictive behaviours, and might explain why early onset cannabis use is a risk factor for 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 highlights the importance of protecting youth from the adverse effects of consumption through greater investment in drug-prevention programs.
"It will be important to conduct similar analyses with this cohort or similar cohorts as they transition to young adulthood, when alcohol and cannabis use become more severe," Conrod said. "This might be particularly relevant for alcohol effects: while this study did not detect effects of teen alcohol consumption on cognitive development, the neurotoxic effects may be observable in specific subgroups differentiated based on the level of consumption, gender or age." Morin added: "We also want to identify if these effects on brain development are related to other difficulties such as poor academic performance, neuroanatomical damage, and the risk of future addiction or mental health disorders."
https://www.sciencedaily.com/releases/2018/10/181003090325.htm