title: Marijuana Use Predicts Cognitive Performance on Tasks of Executive Function.
abstract: OBJECTIVE
  Despite growing evidence that chronic marijuana use is associated with cognitive impairment, particularly when use is initiated at an early age, national trends demonstrate significant decreases in the perceived risk of marijuana corresponding with increased use, especially among youth. The current study assessed the impact of marijuana use on executive function and whether patterns of marijuana use, including earlier age at onset, higher frequency, and increased magnitude of use, predict impairment.
  
  
  METHODS
  Forty-four chronic, heavy marijuana smokers (37 male, 7 female) and 32 healthy, nonsmoking control participants (20 male, 12 female) recruited from the Greater Boston area completed two assessments of executive function: the Stroop Color Word Test and Wisconsin Card Sorting Test (WCST).
  
  
  RESULTS
  Marijuana smokers had poorer executive function relative to control participants, a between-group difference that was primarily driven by individuals with early onset of marijuana use (before age 16; n = 21); significance remained even when controlling for frequency and magnitude of use. Further, earlier age at marijuana onset and increased marijuana use predicted poorer neurocognitive performance, and perseverative errors on the WCST significantly predicted marijuana group membership.
  
  
  CONCLUSIONS
  These findings underscore the impact of early onset of marijuana use on executive function impairment independent of increased frequency and magnitude of use. In addition, poorer performance on the WCST may serve as a neuropsychological marker for heavy marijuana users. These results highlight the need for additional research to identify predictors associated with early marijuana use, as exposure to marijuana during a period of developmental vulnerability may result in negative cognitive consequences.
authors.affiliation: Cognitive and Clinical Neuroimaging Core, McLean Imaging Center, McLean Hospital, Belmont, Massachusetts.|Department of Psychology, Tufts University, Medford, Massachusetts.
authors.forename: Mary Kathryn
authors.initials: MK
authors.lastname: Dahlgren
authors.affiliation: Cognitive and Clinical Neuroimaging Core, McLean Imaging Center, McLean Hospital, Belmont, Massachusetts.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Sagar
authors.affiliation: Cognitive and Clinical Neuroimaging Core, McLean Imaging Center, McLean Hospital, Belmont, Massachusetts.
authors.forename: Megan T
authors.initials: MT
authors.lastname: Racine
authors.affiliation: Cognitive and Clinical Neuroimaging Core, McLean Imaging Center, McLean Hospital, Belmont, Massachusetts.
authors.forename: Meredith W
authors.initials: MW
authors.lastname: Dreman
authors.affiliation: Cognitive and Clinical Neuroimaging Core, McLean Imaging Center, McLean Hospital, Belmont, Massachusetts.|Department of Psychiatry, Harvard Medical School, Boston, Massachusetts.
authors.forename: Staci A
authors.initials: SA
authors.lastname: Gruber
mesh_terms: D000293:Adolescent; D000328:Adult; D003071:Cognition / Q000502:physiology*; D060825:Cognitive Dysfunction / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology*; D056344:Executive Function / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology*; D008385:Marijuana Smoking / Q000009:adverse effects* / Q000453:epidemiology / Q000523:psychology; D009483:Neuropsychological Tests; D011237:Predictive Value of Tests; D011597:Psychomotor Performance / Q000502:physiology*; D055815:Young Adult