Insomnia as a moderator of alcohol use and blackout: Potential role in acute physiological consequences

Background: Alcohol-induced blackout is associated concurrently and prospectively with alcohol-related harm, including emergency room visits and sexual coercion. Although sleep has not been linked empirically to blackout, symptoms of insomnia have also been linked to memory impairment, in which case insomnia symptoms may compound alcohol's negative effects on memory. This study tested insomnia symptoms as a moderator of the association between heavy drinking and alcohol-induced blackout. Methods: Heavy-drinking young adults in college (N = 461, 69% female) completed assessments online from remote locations. Hierarchical linear regression was used to test a moderation model predicting blackout frequency. Logistic regression was used to test post hoc hypotheses. Results: In contrast to our main hypothesis, heavy drinking was more weakly (not more strongly) associated with blackout in the context of more severe insomnia. Post hoc analyses tested insomnia symptoms as a unique moderator of the association between heavy drinking and likelihood of acute physiological consequences of alcohol use (blackout, passing out, nausea/throwing up, and hangover). Insomnia severity at least marginally moderated the association between heavy drinking and 4 out of 5 physiological consequences of alcohol use, and only moderated the association between drinking and 1 of 19 remaining consequences. Conclusions: Symptoms of insomnia are associated with alcohol-related harm, but may buffer associations between drinking and acute physiological consequences of alcohol. Additional research is needed to determine if alcohol heightens sensitivity to the acute physiological effects of alcohol, in which case less alcohol may be required for young adults with insomnia to experience these effects.