MDMA-assisted Prolonged Exposure Therapy for Comorbid Alcohol Use Disorder and Post-traumatic Stress Disorder

Inclusion Criteria: 1. Both AUD and current PTSD according to the DSM-5 criteria, for 6 months or longer with at least moderate severity, according to investigator judgement and CAPS-5 2. Aged ≥18 years old 3. Adequate cognition and English language skills to give valid consent and complete research interviews assessments 4. Willing to give written informed consent 5. Received prior treatment for PTSD or AUD (not including study interventions) 6. Stable housing 7. Able to identify a significant other (such as a family/friend/partner) who could accompany them from clinic/provide transport and/or be contacted by the study team if required Exclusion Criteria: 1. History of, or currently meeting, DSM-5 criteria for: * current or lifetime psychotic or bipolar disorders, or * major depression with psychotic features Assessed via Structured Clinical Interview for DSM-5 - Research Version (SCID-5-RV). Potential participants will be screened for personality disorders but suitability will then be confirmed by clinical interview given the prevalence of high scores in this comorbid population 2. Pregnant or lactating (contraception must be used and a sensitive pregnancy test will be performed at baseline and prior to dosing) 3. Significant alcohol withdrawal (current Clinical Institute Withdrawal Assessment for Alcohol \[CIWA-Ar\] score ≥10, including history of delirium tremens or alcohol withdrawal seizures). 4. Concurrent use of psychotropic medication (antidepressants and alcohol pharmacotherapy use considered if assessed by physician and titrated down with 5 half-lives + 1 week washout) 5. Use of, and unable or unwilling to cease, any medications likely to interact with MDMA in the opinion of the physicians and investigators during the trial (low dose opiates are permitted for pain management but not the night before or after MDMA sessions) 6. Substance use disorder other than tobacco (e.g. benzodiazepines, cannabis) 7. Abnormal clinical findings including a history of, or current: cardiac disease and/or dysrhythmia, uncontrolled hypertension or severe hypotension, abnormal electrocardiogram findings, stroke, liver disease, a history of epilepsy, hyponatraemia, or malignant hyperthermia (controlled hypertension and diabetes type II may be permitted) 8. Suicide risk according to clinician judgement and responses to Columbia Suicide Severity Rating Scale-Lifetime (C-SSRS-L) and SCID-5-RV. • Details surrounding any previous attempts \>6 months ago will be gathered whereby attempts related to their trauma/PTSD and/or associated with the use of psychostimulants will contribute to risk assessment and guide trial safety measures if enrolled 9. Clinically unstable systemic medical (e.g., cancer) or psychiatric disorder or condition that might require hospitalisation that precludes trial participation 10. Regular use of ecstasy (e.g. at least twice in last 6 months, or \>10 times within the last 5 years) 11. Enrolled in any other interventional clinical trials in the previous two months or over the duration of the study