Simultaneous alcohol and marijuana (SAM) use is increasingly prevalent among young adults but has adverse health consequences. The current study examined daily-level associations between perceived sleep health and SAM use, relative to non-substance-use days and alcohol- or marijuana-only days. We also estimated linear associations between alcohol/marijuana use and perceived sleep health and explored whether effects were moderated by combined use of alcohol and marijuana.
A community sample of SAM-using young adults (N=409; Mage=21.61, SD=2.17; 50.9% female; 48.2% White; 48.9% college students) completed twice-daily surveys for five 14-day sampling bursts. Daily measurements assessed substance use and perceived sleep health in terms of subjective sleep quality, negative impact of sleep on functioning, and symptoms of insomnia.
Multilevel models indicated that, relative to non-substance-use days, participants reported poorer perceived sleep health on alcohol-only days, better perceived sleep health on marijuana-only days, and mixed evidence regarding SAM use (i.e., fewer perceived symptoms of insomnia, but poorer perceived next day functioning attributed to sleep). Daily-level estimates showed increased alcohol use was associated with poorer perceived sleep health, while stronger effects from marijuana were associated with better perceived sleep health. Across all indices of sleep health, only one linear association was moderated by combined use: The adverse association between alcohol and next day functioning was weaker on days alcohol was combined with marijuana.
Findings provide additional evidence for daily-level effects of alcohol and marijuana use on perceived sleep health and address an important literature gap regarding potential adverse effects of SAM use.

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