• April D Thames, Natalie Arbid, and Philip Sayegh.
• Department of Psychiatry and Biobehavioral Sciences, University of California Los Angeles, 740 Westwood Plaza C8-226, Los Angeles, CA 90095, United States. Electronic address: athames@mednet.ucla.edu.
• Addict Behav. 2014 May 1; 39 (5): 994-9.

ObjectiveWith the recent debates over marijuana legalization and increases in use, it is critical to examine its role in cognition. While many studies generally support the adverse acute effects of cannabis on neurocognition, the non-acute effects remain less clear. The current study used a cross-sectional design to examine relationships between recent and past cannabis use on neurocognitive functioning in a non-clinical adult sample.MethodOne hundred and fifty-eight participants were recruited through fliers distributed around local college campuses and the community. All participants completed the Brief Drug Use History Form, the Structured Clinical Interview for DSM-IV Disorders, and neurocognitive assessment, and underwent urine toxicology screening. Participants consisted of recent users (n=68), past users (n=41), and non-users (n=49).ResultsRecent users demonstrated significantly (p<.05) worse performance than non-users across cognitive domains of attention/working memory (M=42.4, SD=16.1 vs. M=50.5, SD=10.2), information processing speed (M=44.3, SD=7.3 vs. M=52.1, SD=11.0), and executive functioning (M=43.6, SD=13.4 vs. M=48.6, SD=7.2). There were no statistically significant differences between recent users and past users on neurocognitive performance. Frequency of cannabis use in the last 4 weeks was negatively associated with global neurocognitive performance and all individual cognitive domains. Similarly, amount of daily cannabis use was negatively associated with global neurocognitive performance and individual cognitive domains.ConclusionsOur results support the widespread adverse effects of cannabis use on neurocognitive functioning. Although some of these adverse effects appear to attenuate with abstinence, past users' neurocognitive functioning was consistently lower than non-users.Copyright © 2014 Elsevier Ltd. All rights reserved.

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