Thirty-one percent of the Vietnam-era Veterans have been diagnosed with posttraumatic stress disorder (PTSD). Among those, 70% have also been diagnosed with an alcohol use disorder (AUD). Veterans with PTSD use alcohol to cope with their distressing psychological symptoms such as anxiety. However, alcohol withdrawal effects overlap with PTSD symptoms, thereby reinforcing alcohol consumption to alleviate the PTSD symptoms. Studies have shown that individuals with comorbid PTSD and AUD have increased intensity of alcohol cravings and relapse faster during withdrawal than those with AUD only. The cannabinoid (CB) system plays an important role in both stress and alcohol dependence. Clinical studies have shown that individuals with PTSD have dysregulated levels of the endocannabinoids, 2-arachidonolglycerol (2-AG) and anandamide (AEA). Animal studies have also shown that both 2-AG and AEA concentrations and CB1 receptor protein levels are altered after acute and chronic stress. While extensive research has shown that PTSD or AUD alone affects the CB system, and different durations of ethanol withdrawal alone dysregulate the CB1 receptor, the role of the CB system on the comorbidity of PTSD and alcohol dependence and withdrawal is yet unknown. This knowledge gap will be addressed in this application by elucidating the mechanism by which the comorbidity of PTSD and ethanol dependence and withdrawal dysregulates cannabinoid functions that cause negative health consequences outcomes for our Veterans. The central hypothesis of this project is that PTSD comorbid with ethanol dependence and withdrawal will uniquely dysregulate CB signaling causing an increase in ethanol consumption and anxiety behavior, and that a cannabinoidergic-based intervention will block this effect. Mice will undergo traumatic stress using the single prolonged stress paradigm followed by chronic intermittent ethanol vapor (CIEv) exposure, a model of ethanol dependence. After 4 cycles of CIEv with 5-days of 2-bottle choice drinking tests during intervening weeks, mice will be withdrawn from ethanol for 7, 30, and 60 days. The following three Specific Aims will be tested to support the central hypothesis: 1) Evaluate the effects of traumatic stress and ethanol dependence on ethanol consumption and anxiety behavior as a function of ethanol withdrawal duration. 2) Examine changes in CB signaling associated with ethanol-induced withdrawal behaviors as a factor of withdrawal duration. 3) Evaluate the efficacy of a selective CB1 agonist, methanandamide, to block stress-induced ethanol dependence and withdrawal outcomes.