Psilocybin-Assisted Psychotherapy for the Treatment of Severe Alcohol Use Disorder

This study aims to determine the safety and preliminary efficacy of psilocybin-assisted psychotherapy in improving alcohol-related outcomes among adults with severe alcohol use disorder in a a double-blind, dose-comparison concurrent control, randomized trial. Participants will undergo structured psychotherapy and will be randomized to two psilocybin sessions to receive either a full dose (30mg or 40mg) or low dose (10mg or 15mg).

To be eligible, individuals must be: * English speaking adults between ages 18 and 65 * Diagnosis of DSM5 AUD, severe * Completion of inpatient withdrawal management (i.e. "detox") for AUD within 90 days of enrollment * Amenable to attending all psychotherapy and study visits at BWH CCI * Able to identify an individual who can act as points of contact during the trial * Have a friend or family member who can bring the participant home after the psilocybin sessions and stay overnight Individuals with any of the following will be excluded: * • Any personal history of a psychotic disorder (schizophrenia, schizoaffective disorder, brief psychotic disorder, delusional disorder, schizophreniform disorder, substance-induced psychotic disorder or major depression with psychotic features) or any bipolar-spectrum disorder * Participants with a family history of first-degree relatives with psychotic disorder or bipolar-spectrum disorder * Participants who have a significant suicide risk as defined by current suicidal ideation (Columbia-Suicide Severity Rating Scale (C-SSRS) score 2 to 5) and/or recent (within the past 6 months) active suicidal ideation (C-SSRS score 4 or 5) * Participants who have a history of significant or serious adverse reaction to classic psychedelics * Homicidality within the last six months * History of DSM5 hallucinogen use disorder * Positive breath alcohol level at screening * Need for inpatient withdrawal management for alcohol at the time of screening * Current DSM5 opioid, cocaine, stimulant or sedative/hypnotic use disorder * Systolic blood pressure persistently above 165mmHg during screening * History of hypersensitivity to psilocybin * Use of psilocybin or other psychedelics with 5-HT2B activity in the prior 12 months * Significant EKG abnormalities including QTc prolongation defined as \>450 ms for men and women, or a diagnosis or family history of Long QT syndrome. * History of any cardiac valvulopathy that raises the risk for participation as determined by the cardiology consultant * History of intracranial mass or bleed, seizure disorder other than alcohol withdrawal seizures, liver cirrhosis, renal failure, obstructive lung disease requiring supplemental oxygen, hyperthyroidism, narrow-angle glaucoma, uncontrolled cardiac arrythmias, heart failure * History of head trauma, stroke, or myocardial infarction in one year prior to enrollment. * Expected to require surgical treatment at any point during the trial * Liver dysfunction with LFTs \> 3x upper normal limit at screening and Total bilirubin \> 2.5x the upper normal limit * MRI contraindications (other ferromagnetic implants, body weight greater than 550 lbs., etc.) * Pregnant or breastfeeding * High risk for adverse emotional or behavioral reaction based on the opinion of the study investigators such as evidence of a personality disorder * Currently taking medications with serotonergic activity (other than SSRIs/SNRIs); inhibitors of UGT1A9, UGT1A10, MAO, and aldehyde or alcohol dehydrogenase; antipsychotics (e.g., first and second generation); mood stabilizers (e.g., lithium, valproic acid); or significant inhibitors of UGT enzymes that metabolize psilocin * Selective serotonergic reuptake inhibitors and serotonin and norepinephrine reuptake inhibitors are allowed if participants have been on stable doses of the medication(s) for at least 90 days prior to enrollment. * Currently receiving insulin for blood sugar management.