Prospective Memory and Future Event Simulation in Frequent Cannabis Users

Background. Frequent cannabis users have been found to show impaired memory for past events, but it is not clear whether they are also impaired in prospective memory for future events. Aims. To objectively assess prospective memory (PM) in frequent cannabis users (one group dependent on cannabis, and one group non-dependent) compared to non-using controls, and to examine the effects of future event simulation (FES) on PM performance. To explore depression, anxiety and ‘schizotypy’ across groups. Design. An independent groups design. Setting. University College London. Participants. Fifty-four participants (18 dependent cannabis users, 18 non-dependent cannabis users and 18 controls) took part and were matched on age, gender, and highest level of education. Measures. The Virtual Week was used to assess PM abilities, with and without FES. Other measures: Cannabis Use Potency Questionnaire (CPU-Q), immediate and delayed prose recall, phonemic and category fluency, Spot-the-Word, Beck Depression Inventory (BDI-II), Beck Anxiety Inventory (BAI), and a measure of schizotypy (O-LIFE: Unusual Experiences). Results. There were no group differences in PM performance on the Virtual Week, and FES did not improve PM performance. Dependent cannabis users scored higher on depression, anxiety and schizotypy than both other groups (non-dependent cannabis users and controls, who scored similarly). Conclusions. When carefully matched on baseline variables, cannabis users do not differ from non-using controls on PM. Suggestions for future research are discussed