Long-term effects of frequent cannabis use on working memory and attention: an fMRI study.
BACKGROUND
Excessive use of cannabis may have long-term effects on cognitive abilities. Mild impairments have been found in several cognitive domains, particularly in memory and attention. It is not clear, however, whether these effects also occur with moderate, recreational use of cannabis. Furthermore, little is known about underlying brain correlates.


OBJECTIVE
The aim of this study is to assess brain function in frequent but relatively moderate cannabis users in the domains of working memory and selective attention.


METHODS
Functional magnetic resonance imaging was used to examine verbal working memory and visuo-auditory selective attention in ten frequent cannabis users (after 1 week of abstinence) and ten non-using healthy controls. Groups were similar in age, gender and estimated IQ.


RESULTS
Cannabis users and controls performed equally well during the working memory task and the selective attention task. Furthermore, cannabis users did not differ from controls in terms of overall patterns of brain activity in the regions involved in these cognitive functions. However, for working memory, a more specific region-of-interest analysis showed that, in comparison to the controls, cannabis users displayed a significant alteration in brain activity in the left superior parietal cortex.


CONCLUSIONS
No evidence was found for long-term deficits in working memory and selective attention in frequent cannabis users after 1 week of abstinence. Nonetheless, frequent cannabis use may affect brain function, as indicated by altered neurophysiological dynamics in the left superior parietal cortex during working memory processing.
Jager
Gerry
G
Rudolf Magnus Institute of Neuroscience, Department of Psychiatry, A.01.126, University Medical Center, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands. gjager@umcutrecht.nl
Kahn
Rene S
RS
Van Den Brink
Wim
W
Van Ree
Jan M
JM
Ramsey
Nick F
NF
D000328:Adult; D001288:Attention / Q000187:drug effects*; D001931:Brain Mapping; D002188:Cannabis / Q000633:toxicity*; D002540:Cerebral Cortex / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000187:drug effects*; D013997:Time Factors