Ethnic Differences in the Effects of COVID on the Substance Use Behavior of Emerging Adults - ABSTRACT Little is known about the adverse psychosocial impact of COVID-19 on demographic groups that are already facing significant health disparities. Native Hawaiian and other Pacific Islanders (NHOPI), who are indigenous to Hawaii and other Pacific Islands, face significant health disparities, which often get overlooked because of NHOPI being combined with low-risk Asian groups in national studies. Compared with Asians, NHOPI are at markedly higher risk for mortality and morbidity due to cancer and cardiovascular disease. In addition, tobacco and other substance use prevalence among NHOPI is much higher than among Asians. This proposal seeks to examine ethnic differences in substance use behavior before and after the spread of COVID-19 across Asians and NHOPI, with reference to Whites. In addition, we will test a new model that attempts to explain the mechanisms of the potential increase in substance use post-COVID among emerging adults (18-29 year olds). Informed by the theories of stress-coping, self-medication, and emerging adulthood (EA), the central postulate of the model is that post-COVID increases in financial distress, EA stress, perceived discrimination, loneliness/social isolation, COVID-related anxieties, and negative life events result in increased generalized stress and poorer mental health among emerging adults, which in turn results in increased substance use (tobacco, alcohol, marijuana, and illicit drugs). We hypothesize that NHOPI will show higher exposure to post-COVID financial distress, EA stress, COVID-related anxieties, loneliness, and negative life events, which will eventually lead to higher substance use among NHOPI. Our team has access to a cohort of emerging adults (N=2335; 55% women; 45% Asian, 20% NHOPI, 24% White, 11% Other) from Hawaii, originally recruited as part of research focused on tobacco control. Despite the tobacco focus, the study collected extensive data on other substance use behavior, mental health symptomatology, and EA attributes, which may be compared against post-COVID changes. We have collected 4 waves of pre-COVID data from the cohort in 6-month intervals. The 4th wave of data collection was completed in January 2020, approximately two months before the state of Hawaii halted all non-essential activities in response to the pandemic, including tourism, a mainstay of Hawaii’s economy. The decreased tourism and closure of businesses have resulted in Hawaii’s economy being one of the worst affected in the U.S. The current study plans to resume post-COVID data collection from the cohort for additional 6 waves. The first of the 6 waves is about to be launched in February-March 2021—approximately 1 year after the last pre-COVID survey—using institutional funds. The current proposal seeks to continue data collection every 6 month for 5 more waves. Across the 4 waves of pre- COVID data collection, we retained 89% of the baseline sample, almost all of whom have expressed interest for continued participation in the study. In sum, this study is significant for seeking to advance knowledge about the mechanisms of COVID-related health disparities and innovative for testing a new conceptual model.