Clinical Research Directory

Inclusion Criteria: * Are between 18 and 70 years old. * Able to provide written informed consent. * Fluent in speaking and reading Dutch. * Is a veteran of the Dutch Armed Forces. * Able to swallow pills. * Have a body mass index (kg/m2) of \>18.0. * Meet DSM-5 criteria for current PTSD. * Meet criteria for treatment-refractory PTSD. * Agree to have study visits audiovisually recorded. * Able to provide a contact (relative, spouse, close friend, or other support person) who is willing and able to be reached by the investigators in the event of the participant becoming unwell or unreachable. Exclusion Criteria: * Has a history of any medical condition that could make receiving psilocybin harmful because of temporary increases in blood pressure and heart rate. * Has a medical or psychiatric condition that could interfere with study participation or pose a risk to the participant's safety or well-being. * Has uncontrolled hypertension. * Unable or unwilling to safely taper-off prohibited psychiatric medication. * Has been exposed to electroconvulsive therapy (ECT) within 12 weeks of enrollment. * Has any current problem which, in the opinion of the investigator, might interfere with study participation.