Psilocybin AsSisted pSychotherapy for the treatmENt of Gambling disordER : a Pilot Study

Inclusion Criteria: * Men and women aged 18 years or older * With a confirmed diagnosis of current gambling disorder (diagnostic criteria according to DSM-5), regardless of severity. * Able to complete self-assessment questionnaires * Willing to start addiction treatment, or for whom treatment already undertaken is not sufficient * Willing to undergo a blood test and ECG * Written and oral comprehension of French * Having signed an informed consent form before any procedure under study * Affiliated with a French social security system * Women of childbearing age with a negative pregnancy test and highly effective contraception (according to version 1.2 of March 2024 of the CTCG recommendations in Appendix 7) * Men of childbearing age using effective contraception (according to version 1.2 of March 2024 of the CTCG recommendations). * Negative result on urinary toxicology screening * In the case of psychotropic treatment (excluding nicotine replacement therapy): stabilization of dosage or initiation for more than 1 month. Exclusion Criteria: * Medical conditions that would prevent safe participation in the trial (epilepsy, significantly impaired liver function (TP\<50%), significantly impaired kidney function (GFR\<90 mL/min), coronary artery disease, history of arrhythmia, heart failure, uncontrolled hypertension, history of stroke, severe asthma, hyperthyroidism, narrow-angle glaucoma, symptomatic prostatic hypertrophy, or bladder neck obstruction). * Serious ECG abnormalities (including QTc prolongation = corrected QT) * Current or past psychotic or bipolar disorder * Other unstable psychiatric disorder * Family history (first-degree relatives) of psychotic disorder or type 1 bipolar disorder * Current high risk of suicide (according to the MINI 5.0 suicide risk module) * History of hallucinogen use disorder or any use in the past year * Current alcohol use disorder with a history of withdrawal symptoms * Extreme thinness (BMI \< 16.5) or obesity (BMI \> 30) * Major cognitive impairment (Mini-Mental State Examination score \< 26) * Allergy or hypersensitivity to psilocybin or any of the excipients contained in the investigational drug * Taking UGT1A9, UGT1A10, ALDH, or ADH inhibitors * Pregnancy or breastfeeding * Current protective measures (guardianship and legal protection) * Participation in another interventional research protocol involving another psychotherapeutic or pharmacological intervention that may have an impact on clinical progression