Grant: Doctoral Award - Frederick Banting and Charles Best Canada Graduate Scholarships

People with schizophrenia (SZ) experience problems with their ability to think, concentrate and remember, collectively known as cognitive deficits. Misuse of marijuana (MJ) occurs at high rates in SZ and in the general population. Interestingly, heavy MJ use in healthy individuals can lead to similar cognitive deficits as SZ patients, while studies of chronic MJ use in SZ show both negative and positive effects on cognition. This is surprising since MJ use tends to worsen other symptoms associated with the illness such as hallucinations and depression. It is important to understand this relationship in SZ as cognition predicts overall daily functioning. Most studies examining the effects of MJ on cognition in SZ have compared users to nonusers at one time-point. Thus we propose a unique design. We examined the effects of stopping MJ for one-month on cognitive and psychotic symptoms in daily male MJ users with SZ and without (controls). We also examined its effects on brain activity using electroencephalography (brain waves) and brain (transcranial magnetic) stimulation. We predict half of subjects will quit for one-month and demonstrate improved cognition and less irregular brain activity over time. Psychotic and mood symptoms will also improve. Currently, 7 SZ and 8 controls have completed the study, and by study end in Dec. 2015, this will total 20 and 20 respectively. Participants were assessed at baseline, day 15 and 29 on a variety of cognitive tasks. Weekly visits assessed psychotic, mood, cravings and withdrawal and included a supportive therapy session. Twice weekly urine tests were used to confirm abstinence. Those with negative samples were rewarded throughout the study and given a $300 bonus if end-point abstinence was achieved. Pilot data shows that 5/7 SZ and 6/8 controls achieved end-point abstinence, demonstrating the feasibility of this novel design. We hope our findings lead to better treatment outcomes for cognitive deficits and MJ addictions.