title: Cortical thickness and neurocognition in adolescent marijuana and alcohol users following 28 days of monitored abstinence.
abstract: OBJECTIVE
  Adolescent marijuana use continues to increase in prevalence as harm perception declines. Better understanding of marijuana's impact on neurodevelopment is crucial. This prospective study aimed to investigate cortical thickness and neurocognitive performance before and after 28 days of monitored abstinence in adolescent marijuana and alcohol users.
  
  
  METHODS
  Subjects (N = 54; >70% male) were adolescent marijuana users (ages 15-18 years) with regular alcohol use (MJ + ALC; n = 24) and non-using controls (CON; n = 30) who were compared before and after 4 weeks of sequential urine toxicology to confirm abstinence. Participants underwent magnetic resonance imaging, neuropsychological assessment, and substance use assessment at both time points. Repeated-measures analysis of covariance was used to look at the main effects of group, time, and Group × Time interactions on cortical thickness and neurocognitive functioning. Bivariate correlations estimated associations between cortical thickness, substance use severity, and cognitive performance.
  
  
  RESULTS
  Marijuana users showed thicker cortices than controls in the left entorhinal cortex (ps < .03) before and after monitored abstinence, after adjusting for lifetime alcohol use. More lifetime marijuana use was linked to thinner cortices in temporal and frontal regions, whereas more lifetime alcohol use and heavy episodic drinking episodes was linked to thicker cortices in all four lobes (ps < .05). Age of onset of regular marijuana use was positively related to cortical thickness (ps < .03).
  
  
  CONCLUSIONS
  Adolescent alcohol and marijuana use may be linked to altered longer-term neurodevelopmental trajectories and compromised neural health. Cortical thickness alterations and dose-dependent associations with thickness estimates were observed both before and after monitored abstinence and suggest neural differences continue to persist 28 days after cessation of marijuana use. Neural recovery may be identified with longer follow-up periods; however, observed changes related to use severity could have implications for future psychosocial outcomes.
authors.affiliation: Veterans Affairs (VA) San Diego Healthcare System, La Jolla, California, Department of Psychiatry, University of California San Diego, La Jolla, California.
authors.forename: Joanna
authors.initials: J
authors.lastname: Jacobus
authors.affiliation: Department of Psychiatry, University of California San Diego, La Jolla, California.
authors.forename: Lindsay M
authors.initials: LM
authors.lastname: Squeglia
authors.affiliation: Veterans Affairs Puget Sound Healthcare System, Seattle, Washington.
authors.forename: Scott F
authors.initials: SF
authors.lastname: Sorg
authors.affiliation: Department of Psychiatry, University of California San Diego, La Jolla, California, San Diego State University/University of California San Diego Joint Doctoral Program in Clinical Psychology, San Diego, California.
authors.forename: Tam T
authors.initials: TT
authors.lastname: Nguyen-Louie
authors.affiliation: Veterans Affairs (VA) San Diego Healthcare System, La Jolla, California, Department of Psychiatry, University of California San Diego, La Jolla, California.
authors.forename: Susan F
authors.initials: SF
authors.lastname: Tapert
mesh_terms: D000293:Adolescent; D064829:Alcohol Abstinence / Q000523:psychology; D000437:Alcoholism / Q000175:diagnosis* / Q000523:psychology; D002540:Cerebral Cortex / Q000254:growth & development* / Q000473:pathology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000175:diagnosis* / Q000523:psychology; D009483:Neuropsychological Tests; D011446:Prospective Studies; D013997:Time Factors