Circulating Oxytocin Changes in Response to MDMA vs. Placebo in Adult Patients With Autism Spectrum Disorder and Matched Healthy Controls

Inclusion Criteria for patients: * Adult patients with a confirmed diagnosis of autism spectrum disorder level 1 according to Diagnostic and Statistical Manual (DSM) V Inclusion criteria for healthy controls: * Adult healthy controls * Matched for age, sex, BMI, and oestrogen replacement/menopause/hormonal contraceptives to patients * No medication, except hormonal contraception * A score of \<32 in the Autism Spectrum Quotient Exclusion Criteria: * Participation in a trial with investigational drugs within 30 days * Illicit substance use (except for cannabis) more than 10 times in lifetime or any time within the previous two months * Consumption of alcoholic beverages \>15 drinks/week * Tobacco smoking \>10 cigarettes/day * Cardiovascular disease (coronary artery disease, heart failure, left ventricular ejection fraction (LVEF) \<40%, stroke in the last 3 months, atrial fibrillation/flutter, Wolff-Parkinson-White (WPW)-Syndrome) * Uncontrolled arterial hypertension (\>140/90 mmHg) or hypotension (\<85mmHg) * Current or previous major psychiatric disorder (e.g., major depression, schizophrenia spectrum disorder) * Psychotic disorder in first-degree relatives * Pregnancy and breastfeeding * Diagnosed CKD \> grade III (GFR \< 30ml/min) * Diagnosed liver cirrhosis or alanine aminotransferase (ALAT) or aspartate aminotransferase (ASAT) levels 2.5 times above the normal range * Confirmed epilepsy diagnosis * Diagnosed autism spectrum disorder level 2 or 3 (according to DSM V criteria)