The impact of early-onset cannabis use on functional brain correlates of working memory

• Published in: Progress in neuro-psychopharmacology & biological psychiatry 2010-08, Vol.34 (6), p.837-845
• Main Authors: Becker, Benjamin, Wagner, Daniel, Gouzoulis-Mayfrank, Euphrosyne, Spuentrup, Elmar, Daumann, Jörg
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Age Factors; Age of Onset; Analysis of Variance; Biological and medical sciences; Brain Mapping; Cannabis; Cannabis - adverse effects; Cerebral Cortex - drug effects; Cerebral Cortex - physiopathology; fMRI; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Marijuana Smoking - adverse effects; Marijuana Smoking - physiopathology; Medical sciences; Memory, Short-Term - drug effects; Neuromaturation; Neuropharmacology; Neuropsychological Tests; Parietal cortex; Pharmacology. Drug treatments; Statistics, Nonparametric; Working memory
• ISSN: 0278-5846; 1878-4216
• DOI: 10.1016/j.pnpbp.2010.03.032

Cannabis is the most commonly used illicit drug. Prevalence rates are particularly high among adolescents. Neuropsychological studies have identified cannabis-associated memory deficits, particularly linked to an early onset of use. However, it remains unclear, whether the age of onset accounts for altered cortical activation patterns usually observed in cannabis users. Functional magnetic resonance imaging was used to examine cortical activation during verbal working memory challenge in (1) early-onset (onset before the age of sixteen; n = 26) and (2) late-onset cannabis users (age at onset at least sixteen; n = 17). Early-onset users showed increased activation in the left superior parietal lobe. Correlational analyses confirmed the association between an earlier start of use and increased activity. Contrariwise neither cumulative dose, frequency nor time since last use was significantly associated with cortical activity. Our findings suggest that an early start of cannabis use is associated with increased cortical activation in adult cannabis users, possibly reflecting suboptimal cortical efficiency during cognitive challenge. The maturing brain might be more vulnerable to the harmful effects of cannabis use. However, due to a lack of a non-using control group we cannot exclude alternative interpretations.