Visuospatial memory impairments in cannabis users

Background: This paper investigates the possibility, arising from previous findings from our laboratories, that cannabis consumption may make a separate contribution to visuospatial memory deficits from those related to ecstasy (MDMA) consumption. Method: Group was a between-participants independent variable at three levels; ecstasy and cannabis users (n = 11), cannabis users (n = 14), and controls (n = 14). Measures of self-reported substance use, IQ, mood, simple visuospatial span (ie. maintenance only), visuospatial working memory span (maintenance plus processing), and demographic variables were obtained. Results: Cannabis users who had not used ecstasy showed significant deficits in both simple visuospatial span and visuospatial working memory span compared to the other two groups. Whilst performing consistently worse than controls, deficits in relation to cannabis users who had also used ecstasy depended upon the selection of covariates. Conclusions: Deficits in simple visuospatial memory may be related to cannabis use, with differences in levels and patterns of its consumption between the two user groups possibly being responsible for these results. Lower ecstasy consumption than that reported by previous samples may have been responsible for the lack of a significant difference in visuospatial working memory performance compared to controls, in contrast to earlier findings.