Marijuana use is common in adolescence, yet neural consequences have not been well delineated. This review seeks to ascertain whether heavy marijuana use in adolescence is associated with persistent neurocognitive abnormalities, and whether adolescents are more vulnerable to the impact of chronic marijuana use than adults.Among heavy marijuana using adults, neurocognitive deficits are apparent for several days following use, but may disappear after one month of abstinence. Studies of adolescent heavy users have identified impairments in learning and working memory up to six weeks after cessation, suggesting persisting effects, yet raise the possibility that abnormalities may remit with a longer duration of abstinence.Given ongoing neuromaturation during youth, adolescents may be more vulnerable to potential consequences of marijuana use than adults. This is supported by rodent models, which show greater memory impairments in animals exposed to cannabinoids as adolescents relative to those exposed as adults. Further, adult humans who initiated use in early adolescence show greater dysfunction than those who began use later. Together, these results suggest that adolescents are more vulnerable than adults to neurocognitive abnormalities associated with chronic heavy marijuana use; however, the impact of preexisting risk factors is unknown.Adolescents demonstrate persisting deficits related to heavy marijuana use for at least six weeks following discontinuation, particularly in the domains of learning, memory, and working memory. Further, adolescents appear more adversely affected by heavy use than adults. Longitudinal studies will help ascertain whether preexisting differences contribute to these abnormalities.
KeywordsAdolescence; marijuana; cannabis; cognition; brain; development Marijuana is the most commonly used preparation of the psychoactive drug, Δ-9-tetrahydrocannabinol (THC), and is consistently the most widely used illicit drug among teenagers, and most users first experiment in adolescence [1]. While 17% of 8th graders have tried marijuana, by 12th grade almost half of teens have used [1,2]. After initial experimentation, many youths develop a regular pattern of use, with 20% of 12th graders reporting use in the past month, and 5% of 12th graders reporting daily use [2]. Adolescence *Address correspondence to this author at the Department of Psychiatry, University of California, 3350 La Jolla Village Drive, 151B San Diego, CA 92161, USA; Tel: (858)552-8585 x5592; stapert@ucsd.edu.
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Author ManuscriptCurr Drug Abuse Rev. Author manuscript; available in PMC 2010 February 19.
Published in final edited form as:Curr Drug Abuse Rev. 2008 January ; 1(1): 99-111.
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NIH-PA Author Manuscriptis also a period of continued neuromaturation, yet the potential neural consequences of marijuana use during these developments have not been well established, and may have implications for academic, occupational, and social achievements. This review will a...