Use and co-use of tobacco and cannabis among couples impacted by alcohol use disorder.

Background: Tobacco and cannabis are common among individuals with alcohol use disorder (AUD); however, co-use is less understood among couples impacted by AUD.Objectives: This study characterized alcohol, tobacco, and cannabis co-use among individuals with AUD (i.e. identified patient; IP) and partners in two dyadic AUD samples separately. It also examined associations within individuals (i.e. intrapersonal) and between partners for the same (i.e. intraclass) and different substances (i.e. interpersonal).Methods: This is a secondary analysis of 96 treatment-seeking couples with AUD (N = 192, 96.9% mixed-sex couples, 51% female) and 46 non-treatment seeking couples with AUD and intimate partner violence (N = 92, 87.0% mixed-sex couples, 56.5% female), separately.Results: Among IPs, alcohol-cannabis co-use ranged from 31.3%-45.7%; alcohol-tobacco co-use ranged from 19.8%-30.4%; and alcohol-tobacco-cannabis use ranged from 10.4%-17.4%. In the treatment-seeking sample, one partner's quantity of tobacco use correlated with their partner's frequency of use (r = .39); Partners demonstrated similarities in tobacco quantity (r = .30) and frequency (r = .45). For the non-treatment-seeking one partner's quantity of tobacco use correlated with their partner's frequency of tobacco use (r = .72) and between one partner's frequency of tobacco use and their partner's quantity of alcohol use (r = .30). Partners demonstrated similarities in tobacco quantity (r = .81), and frequency (r = .62), and frequency of alcohol use (r = .37).Conclusions: Findings suggest that couples demonstrate interdependent patterns of substance use, and preliminary support for a tobacco-alcohol cross-effect suggesting partner influences may be relevant across, not just within, substance types.