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Neuropsychological functioning in adolescent marijuana users: Subtle deficits detectable after a month of abstinence

Published online by Cambridge University Press:  14 August 2007

KRISTA LISDAHL MEDINA
Affiliation:
Department of Psychiatry, University of California, San Diego, California Psychology Department, VA San Diego Healthcare System, San Diego, California
KAREN L. HANSON
Affiliation:
Psychology Department, VA San Diego Healthcare System, San Diego, California Department of Psychology, San Diego State University, California
ALECIA D. SCHWEINSBURG
Affiliation:
Psychology Department, VA San Diego Healthcare System, San Diego, California Department of Psychology, University of California, San Diego, California
MAIRAV COHEN-ZION
Affiliation:
Department of Psychiatry, University of California, San Diego, California Psychology Department, VA San Diego Healthcare System, San Diego, California
BONNIE J. NAGEL
Affiliation:
Department of Psychiatry, Oregon Health and Science University, Portland, Oregon
SUSAN F. TAPERT
Affiliation:
Department of Psychiatry, University of California, San Diego, California Psychology Department, VA San Diego Healthcare System, San Diego, California

Abstract

In adults, studies examining the long-lasting cognitive effects of marijuana use demonstrate subtle deficits in attention, executive function, and memory. Because neuromaturation continues through adolescence, these results cannot necessarily generalize to adolescent marijuana users. The goal of this study was to examine neuropsychological functioning in abstinent marijuana using and demographically similar control adolescents. Data were collected from 65 adolescent marijuana users (n = 31, 26% females) and controls (n = 34, 26% females) 16–18 years of age. Extensive exclusionary criteria included independent psychiatric, medical, and neurologic disorders. Neuropsychological assessments were conducted after > 23 days of monitored abstinence. After controlling for lifetime alcohol use and depressive symptoms, adolescent marijuana users demonstrated slower psychomotor speed (p < .05), and poorer complex attention (p < .04), story memory (p < .04), and planning and sequencing ability (p < .001) compared with controls. Post hoc analysis revealed that the number of lifetime marijuana use episodes was associated with poorer cognitive function, even after controlling for lifetime alcohol use. The general pattern of results suggested that, even after a month of monitored abstinence, adolescent marijuana users demonstrate subtle neuropsychological deficits compared with nonusers. It is possible that frequent marijuana use during adolescence may negatively influence neuromaturation and cognitive development. (JINS, 2007, 13, 807–820.)

Type
Research Article
Copyright
2007 The International Neuropsychological Society

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