Does tobacco dependence worsen cannabis withdrawal in people with and without schizophrenia-spectrum disorders?

Background and ObjectivesRates of cannabis use disorder (CUD) are higher in people with schizophrenia than in the general population. Irrespective of psychiatric diagnosis, tobacco co-use is prevalent in those with CUD and leads to poor cannabis cessation outcomes. The cannabis withdrawal syndrome is well-established and increases cannabis relapse risk. We investigated whether cannabis withdrawal severity differed as a function of high versus no/low tobacco dependence and psychiatric diagnosis in individuals with CUD. MethodMen with CUD (N = 55) were parsed into four groups according to schizophrenia diagnosis and tobacco dependence severity using the Fagerstrom Test for Nicotine Dependence (FTND): men with schizophrenia with high tobacco dependence (SCT+, n = 13; FTND >= 5) and no/low tobacco dependence (SCT-, n = 22; FTND <= 4), and nonpsychiatric controls with high (CCT+, n = 7; FTND >= 5) and no/low (CCT-, n = 13; FTND <= 4) tobacco dependence. Participants completed the Marijuana Withdrawal Checklist following 12-h of cannabis abstinence. ResultsThere was a significant main effect of tobacco dependence on cannabis withdrawal severity (p < .001). Individuals with high tobacco dependence had significantly greater cannabis withdrawal severity (M = 13.85 [6.8]) compared to individuals with no/low tobacco dependence (M = 6.49, [4.9]). Psychiatric diagnosis and the interaction effects were not significant. Lastly, cannabis withdrawal severity positively correlated with FTND (r = .41, p = .002). Conclusion and Scientific SignificanceAmong individuals with CUD and high tobacco dependence, cannabis withdrawal severity was elevated twofold, irrespective of diagnosis, relative to individuals with CUD and no/low tobacco dependence. Findings from this study emphasize the importance of addressing tobacco co-use when treating CUD.