Cheers to tomorrow? Alcohol use predicts poorer mood and well-being the next day in young adults

Alcohol use is embedded within university culture. While the consequences of alcohol use on next-day physical health are well-known, less is known about the consequences to next-day emotional health. This study investigated the relationship between alcohol use and next-day mood and well-being using two daily diary studies with New Zealand university students. Participants completed a daily diary for 13 days (Study 1, n = 1114; 30.6% men, M_age = 19.6) or 7 days (Study 2, n = 212; 24.5% men, M_age = 19.4) where they reported previous night's alcohol consumption and sleep quality, along with today's mood and well-being. Night-time alcohol consumption was categorised into low-risk (women 1-4 drinks, men 1-5 drinks), medium-risk (women 5-9 drinks, men 6-11 drinks) and high-risk (women 10+ drinks, men 12+ drinks) according to New Zealand public health guidelines. Across both studies, medium- and especially high-risk drinking, but not low-risk drinking, was associated with lower next-day positive mood and well-being compared to nondrinking days. Poorer sleep quality partially accounted for the relationship of drinking with next-day mood and well-being in Study 1, but less so in Study 2. Findings suggest that interventions could promote lower risk drinking behaviours to benefit students' well-being.