Association of Cannabis Use and Neurodevelopment Among Adolescents

Abstract

Source: Albaugh MD, Ottino-Gonzalez J, Sidwell A, et al Association of cannabis use during adolescence with neurodevelopment [published online ahead of print June 16, 2021]. JAMA Psychiatry. doi:10.1001/jamapsychiatry.2021.1258Investigators from multiple institutions reviewed data from a longitudinal study to assess the association between cannabis use during adolescence and cerebral cortical thickness development as measured using MRI. Participants were enrolled in the IMAGEN study, conducted across 8 European sites, when they were approximately 14 years old. Using a standard protocol, MRI scans were obtained of the adolescents’ brains at enrollment and a 5-year follow-up visit. In addition, at baseline and at follow-up, study participants completed the European School Survey Project on Alcohol and Other Drugs (ESPAD), in which lifetime use of alcohol, nicotine, and cannabis is self-reported using a 7-point scale with usage ranging from “never” to “>40 times.” Only youths who reported never using cannabis at baseline and had baseline and 5-year data were included in the present study. At the 5-year follow-up, participants also completed the Barratt Impulsiveness Scale, a 30-item self-report that assesses 3 domains of impulsiveness (attentional, non-planning, and motor). Alcohol consumption was estimated at baseline and 5-year follow-up with the Alcohol Use Disorders Identification Test Consumption scale.Cross-sectional regression models were used to assess the association between lifetime cannabis use and local cortical thickness. Longitudinal models were used to identify areas of accelerated age-related cortical thinning associated with cannabis use and to evaluate the association between the 3 domains of impulsiveness as measured by the Barratt Impulsiveness Scale.A total of 799 youths who were cannabis-naïve at baseline were included in the analyses. Mean age of these participants at baseline was 14.0 ±0.4 years, and 56.3% were female. At the 5-year follow-up, 208 participants (26.0%) reported 1-9 lifetime uses of cannabis, and 161 (20.2%) reported 10 to >40 uses. On cross-sectional analysis, there was a dose-dependent, statistically significant negative association between cortical thickness in the left prefrontal and right prefrontal cortices and lifetime cannabis use assessed at the 5-year follow-up. No statistically significant relationships were found between lifetime cannabis use and cortical thickness on baseline MRI results, suggesting that differences observed at follow-up did not precede cannabis use. On longitudinal analysis, statistically significant associations between accelerated age-related thinning in both the left and right prefrontal cortices were found. There was no significant difference in the effects of cannabis on cortical thickness between females and males in either the cross-sectional or longitudinal analyses. Cannabis-related cortical thinning in the right dorsomedial prefrontal cortex was significantly associated with more attentional impulsiveness as measured by the Barratt Impulsiveness Scale.The authors conclude that cannabis use during adolescence was associated with altered neurodevelopment.Dr Doolittle has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.Cannabis use has become more popular and socially accepted in recent years. Many states have decriminalized marijuana use and expanded licensing for dispensaries.1 Nearly 50% of adolescents consider marijuana to be easily accessible, and 28% believe it to have no or low health risks.1 Nearly 1 in 10 persons older than 12 years of age has used marijuana within the past month.2 Large studies of marijuana derivatives, such as tetrahydrocannabinol and cannabidiol, have demonstrated improvement in a range of medical conditions, such as chemotherapy-related nausea, spasticity in multiple sclerosis, and chronic pain.3,4 As marijuana becomes more widely accepted, however, its deleterious effects are often overlooked. This is especially important among adolescents, whose cerebral cortex has not yet fully matured.5 In fact, the current authors describe thinning of the cerebral cortex of adolescent brains based on the cumulative dose of marijuana ingested. In addition, these anatomic effects are associated with a measurable behavioral change: attentional impulsiveness.While the decriminalization of marijuana has resulted in important legal reform, marijuana is best regarded as a drug, akin to alcohol. Use by adolescents ought to be discouraged, except when its medical benefit exceeds its potential harmful effect. While the investigators in the current study do not address the impact of marijuana beyond the 5-year follow-up, other large population studies highlight the association of marijuana use and harmful outcomes, such as respiratory problems, increased depression and anxiety, impaired executive function, poor school performance, and poverty.6,7The current study is the largest longitudinal study of its kind, making an important contribution to ongoing debate of marijuana’s harm and efficacy. Despite marijuana’s increasing popularity, pediatric caregivers should continue to advise caution.Marijuana use among adolescents is associated with cortical thinning and increased impulsiveness.