Individuals with posttraumatic stress disorder (PTSD) have greater prevalence of alcohol use disorders (AUDs), with this comorbidity associated with worse illness outcomes, yet there remains limited mechanistic understanding of how PTSD confers risk for AUD. Understanding risk factors that associate with and predict the development of AUDs in PTSD could inform interventions and prevention efforts to reduce the rate of this comorbidity and improve outcomes of both disorders. Identifying predictors of risk requires longitudinal studies in PTSD aimed at capturing the mechanisms leading to the emergence of AUDs. There is growing evidence PTSD is related to biased decision-making during approach-avoidance conflict. Alcohol is also suggested to alter approach-avoidance decision-making. AUDs and acute alcohol intoxication is associated with a bias to seek out reward despite the possibility of threat (e.g., contributing to relapse following alcohol cue exposure and risky behavior during intoxication respectively). Alcohol-induced changes in approach-avoidance decision-making have not been investigated in the context of PTSD, but emerging data support the investigators' hypothesis that an interaction between alcohol and approach-avoidance conflict in PTSD may occur and contribute to risk for alcohol misuse and development of alcohol problems. No current data, cross-sectional or longitudinal, have tested the role of alcohol-induced changes in approach-avoidance conflict as a mechanism of risk for AUD among individuals with PTSD. To address this gap, the investigators propose to leverage the group's expertise in placebo-controlled alcohol administration procedures, longitudinal modeling, functional neuroimaging, and computational neuroscience approaches to investigate the effects of acute alcohol on approach-avoidance decision-making and mediating changes in multivariate neurocircuitry patterns in limbic, striatal, and salience networks.