Indirect effects of perceived stress and depression on the relationship between insomnia symptoms and hazardous drinking

Insomnia is a risk factor for hazardous drinking, yet the mechanisms underlying this risk are not well characterized. Two factors that might contribute to the relationship between insomnia and drinking are stress and depression. Insomnia is strongly associated with increased stress and depression, which are, in turn, strongly linked to hazardous drinking. Here we conducted a preliminary investigation to determine whether perceived stress and depression indirectly explain the relationship between insomnia and hazardous drinking. Heavy drinkers with self-reported insomnia (n = 405: 270 women, 134 men, 1 non-binary) completed self-report measures of hazardous drinking, insomnia, perceived stress, and depression. Results from our primary cross-sectional parallel mediation model with insomnia as the predictor and hazardous drinking as the outcome showed that, when accounting for the influence of both perceived stress and depression, there was a partial indirect effect of insomnia on hazardous drinking through perceived stress, 95% CI [0.014, 0.205], but not depression, 95% CI [-0.080, 0.172]. In our competing cross-sectional parallel mediation model with hazardous drinking as the predictor and insomnia as the outcome, there was a partial indirect effect of hazardous drinking on insomnia through depression 95% CI [0.016, 0.059], but not perceived stress 95% CI: [-0.026, 0.011]. Results suggest that insomnia may be related to hazardous drinking through its effects on stress and that hazardous drinking may be related to insomnia through its effects on depression. These findings lay the groundwork for future longitudinal studies assessing the causal roles of stress and depression in the insomnia-AUD relationship.