Effect of Cannabis Use on Alcohol Craving and Consumption among those in Alcohol Treatment - PROJECT SUMMARY/ABSTRACT Among those with AUD, cannabis is the most commonly used psychoactive substance. Although initial evidence suggests an overall detrimental impact of cannabis use (CU) on longitudinal AUD treatment outcomes, there is significant divergence about how CU impacts alcohol consumption and craving. Competing theories about the association between CU and alcohol focus on whether CU acts as a substitute (i.e., replacing the effects of alcohol, resulting in decreased craving, use, and harms) or complement (i.e., enhancing the effects of alcohol, resulting in increased craving, use, and harms). Preliminary work in non- treatment engaged samples suggests important mechanisms (e.g., craving) and moderators (e.g., frequency of CU, history of simultaneous use, trait impulsivity) may elucidate these competing theories. An important gap in the literature is in the examination of prospective and momentary effects of naturalistic CU on alcohol craving and consumption among individuals in alcohol treatment. The proposed study aims to address this gap using an intensive longitudinal design to comprehensively examine within- and between-person patterns of CU on alcohol outcomes over the critical first year after treatment initiation. Key outcomes among those early in treatment are alcohol craving and risky alcohol consumption patterns (rate of consumption and volume consumed). Use of alcohol biosensors allow for the objective measurement of these alcohol consumption patterns as they naturally occur. The proposed project will be the most comprehensive examination to date of the impact of CU on alcohol treatment outcomes and the first to examine these associations in the natural environment using the BACtrack Skyn to passively mesure transdermal alcohol concentration (TAC). Alcohol craving will be measured as an important outcome of CU in the moment, as well as a mechanism by which CU leads to alcohol consumption. A longitudinal ecological momentary assessment (EMA) burst design (four 10- day bursts at baseline, 1, 2, and 3 months) will be used to isolate the momentary impact of CU on alcohol craving and consumption (measured via TAC) in a stratified sample of recent cannabis users. Following this EMA phase, participants will engage in 6, 9, and 12 month follow-ups to fully capture CU and alcohol patterns/AUD remission over the first year after treatment initiation. This research will directly inform: a) clinical decision-making about the risks of CU during alcohol treatment, b) future intervention development for AUD, and c) policy in the wake of expanding cannabis legalization; and is well-aligned with the objectives of the Collaborative Research on Addiction at NIH.