Inclusion Criteria:
* Participants with AUD will have a current diagnosis of AUD according to DSM-5 criteria (i.e., SCID-5 ascertained diagnosis, confirmed by the Principal Investigators);
* Participants with AUD will meet the following drinking criteria: males will drink \> 14 drinks per week and exceed 4 drinks per day at least twice per week; females will drink \> 7 drinks per week and exceed 3 drinks per day at least twice per week. They must meet drinking criteria during a consecutive 30-day period within the 90 days prior to intake;
* Participants with AUD will indicate willingness to abstain from alcohol and engage in a quit attempt;
* Healthy subjects will have no current or past diagnosis of AUD or other significant substance use disorder. They will drink less than 5 alcoholic drinks per week with no heavy drinking days (i.e., \>4 drinks/day for men; \>3 drinks/day for women) in the last 30 days;
* Able to read and write English and to provide voluntary, written informed consent;
* Agree to have blood drawn for genotyping of the OPRM1 which has been shown to impact the \[11C\]CFN outcome measure, BPND50.
Exclusion Criteria:
* Current significant medical condition such as neurological, cardiovascular, endocrine, renal, liver, or thyroid pathology that would impact the integrity of the data (note that elevated liver enzymes for individuals with AUD will not be exclusionary);
* Past or current neurological disorder or disorders affecting the brain including but not limited to multiple sclerosis, history of stroke, brain tumors, traumatic brain injury with loss of consciousness, seizure disorder;
* Current significant psychiatric disorder including severe substance use disorder (other than alcohol or tobacco use disorders\*), and past or current psychotic symptoms;
* Regular use in the past 6 months of any prescription, psychoactive or herbal medications (e.g., antidepressants, antipsychotics, anxiolytics) that would impact the integrity of the data (e.g., naltrexone); No subject will be asked to stop taking medication to participate in the study;
* Women who are pregnant or nursing, or fail to use one of the following methods of birth control unless she or her partner is surgically sterile or she is postmenopausal (hormone contraceptives \[oral, implant, injection, patch, or ring\], contraceptive sponge, double barrier \[diaphragm or condom plus spermicide\], or IUD;
* Contraindications to MRI such as claustrophobia or metal in their body;
* Subjects whose participation would cause them to exceed yearly radiation limits for research subjects
