Changes in tobacco consumption in cannabis dependent patients with schizophrenia versus non-psychiatric controls during 28-days of cannabis abstinence.

Background: Tobacco and cannabis are highly co-morbid in the general population and in patients with schizophrenia. Given the putative causal mechanisms facilitating co-use, it is important to determine how cannabis cessation may influence concurrent tobacco use. Using a 28-day cannabis abstinence paradigm, we prospectively examined changes in tobacco consumption in patients with schizophrenia and controls with cannabis dependence and daily cigarette use.

Methods: Cannabis dependent patients with schizophrenia (n = 19) and controls (n = 20) completed the study with abstinence rates of 42% and 55%, respectively. Participants completed measures of substance use, withdrawal, and clinical symptoms weekly. Urine samples were collected twice weekly to biochemically verify abstinence.

Results: Patients reported a greater increase in cigarettes smoked per day (CPD) on Day 7 relative to baseline (2.97 cigarette increase for abstinent subgroup, p < .01) compared to controls (.06 cigarette increase for abstinent subgroup, p = .95). Initially, greater reductions in cannabis use related to greater increases in CPD relative to baseline in the patient subsample (simple slope = -2.31, p = .05), but by Day 28, CPD returned to baseline levels independent of cannabis use. CPD changes were unrelated to cannabis withdrawal. Results were similar for changes in caffeine consumption, but not for alcohol.

Conclusions: Findings suggest transient tobacco substitution for cannabis in patients with schizophrenia. This provides further support for a strong association between cannabis and tobacco in schizophrenia. Future studies should focus on targeting underlying mechanisms that promote co-use to better address potential changes in concurrent substance use during treatment interventions.