EVIDENCE FOR A SEX-SPECIFIC RESIDUAL EFFECT OF CANNABIS ON VISUOSPATIAL MEMORY

Background: In an exploratory study, we used a novel computerized batt ery of neuropsychological tests of attention to assess residual cognit ive impairment in marijuana users. Methods: We compared 25 college stu dents who were heavy marijuana smokers (who had smoked a median of 29 days in the last 30 days) with 30 students who were light smokers (who had smoked a median of 1 day in the last 30 days). All subjects were tested after a supervised period of abstinence from marijuana and othe r drugs lasting at least 19 h. Results: Differences between the overal l groups of heavy and light smokers did not reach statistical signific ance on the four subtests of attention administered. However, upon exa mining data for the two sexes separately, marked and significant diffe rences were found between heavy- and light-smoking women on the subtes t examining visuospatial memory. On this test, subjects were required to examine a 6 x 6 'checkerboard' of squares in which certain squares were shaded. The shaded squares were then erased and the subject was r equired to indicate with the mouse which squares had formerly been sha ded. Increasing numbers of shaded squares were presented at each trial . The heavy-smoking women remembered significantly fewer squares on th is test, and they made significantly more errors than the light-smokin g women. These differences persisted despite different methods of anal ysis and consideration for possible confounding variables. conclusions : This observation suggests that it may be important to study the resi dual effects of marijuana on men and women separately - particularly s ince women have been greatly underrepresented in previous studies in t his area.