Evaluating Repetitive Transcranial Magnetic Stimulation (rTMS) for the Treatment of Cannabis Dependence and Working Memory in Patients With Early Psychosis

Cannabis use during adolescence represents a significant risk factor for the development of psychosis including schizophrenia. Moreover, cannabis is the most commonly used drug among patients with an existing psychotic disorder. An estimated 25% of patients with psychosis reportedly meet the criteria of a cannabis use disorder particularly among younger patients experiencing their first episode. Cannabis use significantly exacerbates symptomatology resulting in an increased duration of the first hospitalization visit, number of hospital readmissions, and overall reduced functional outcome. Discovering novel strategies to treat the underlying pathophysiology of cannabis dependence early in the disorder may translate into improved functional outcome. Working memory deficits have been shown to predict relapse in the first-year of psychosis and is modulated with cannabis use. Repetitive transcranial magnetic stimulation (rTMS) targeted to the dorsolateral prefrontal cortex (DLPFC) has shown tremendous promise for the treatment of both tobacco dependence and working memory impairment in patients with psychosis possibly through the modulation of gamma (30-50 Hz) oscillations. The proposed study will therefore evaluate the effect of rTMS on abstinence, working memory performance, and gamma oscillations through a randomized, double-blind, placebo-controlled 28-day longitudinal abstinence study design in patients with early psychosis. It will further explore if baseline performance and gamma oscillations predict abstinence in response to rTMS. It is hypothesized that active compared to sham rTMS will improve abstinence rates and improve working memory performance through the modulation of gamma oscillations.