Bidirectional associations between sleep and cannabis and alcohol (co‐)use in daily life

Background Poor sleep is common in the context of cannabis use, but experimental and daily‐life studies provide mixed evidence for whether cannabis use helps or disturbs same‐night sleep. Despite a high prevalence of co‐use of alcohol and cannabis, most studies of cannabis use and sleep do not consider alcohol use. We sought to add to this literature by examining associations between cannabis and sleep in the context of alcohol co‐use and to examine these associations bidirectionally using ecological momentary assessment. Methods Participants were 88 adults reporting cannabis use at least 3×/week and simultaneous alcohol and cannabis use at least 2×/week. For 14 days, participants completed morning surveys assessing hours slept and perceived sleep quality from the night before. In morning surveys, random surveys, and substance‐specific surveys, participants also reported on alcohol and cannabis craving, use, and amounts. Results Primary results from multilevel models demonstrated that cannabis use was not independently associated with sleep (duration or quality). However, cannabis use attenuated alcohol's negative effects on sleep quality. Conclusions Results question the utility of cannabis use to improve sleep but highlight the attenuated negative effects of alcohol as a potential reinforcer of alcohol‐cannabis co‐use. Future work should continue to consider polysubstance use and integrate additional self‐report and objective measures of sleep health to further clarify how cannabis use affects sleep. On drinking days, cannabis co‐use attenuated the association between total daily drink number and worse sleep quality.