A Study of Psilocybin for PTSD

Eligibility Criteria

• * 21 to 75 years old
• * Have given written informed consent
• * Have a confirmed DSM-5 diagnosis of Post-Traumatic Stress Disorder with symptom duration \>= 6 months
• * Have a baseline CAPS-5 score of \>=35
• * Currently taking a serotonin reuptake inhibitor (e.g. selective serotonin reuptake inhibitor (SSRI), serotonin and norepinephrine reuptake inhibitor (SNRI), at a stable dose for at least two weeks.
• * Be judged by study team clinicians to be at low acute risk for suicidality
• * Be medically stable as determined by screening for medical problems via a personal interview, a medical questionnaire, a physical examination, an electrocardiogram (ECG), and routine medical blood and urinalysis laboratory tests
• * Agree to consume approximately the same amount of caffeine-containing beverage (e.g., coffee, tea) that he/she consumes on a usual morning, before arriving at the research unit on the mornings of drug session days. If the participant does not routinely consume caffeinated beverages, he/she must agree not to do so on session days.
• * Agree to refrain from using any psychoactive drugs, including alcoholic beverages within 24 hours of each drug administration. The exception is caffeine and nicotine.
• * Agree not to take any as needed (PRN) medications on the mornings of drug sessions
• * Agree not to take sildenafil (Viagra®), tadalafil, or similar medications within 72 hours of each drug administration.
• * Agree that for one week before each drug session, he/she will refrain from taking any nonprescription medication, nutritional supplement, or herbal supplement except when approved by the study investigators. Exceptions will be evaluated by the study investigators and will include acetaminophen, non-steroidal anti-inflammatory drugs, and common doses of vitamins and minerals.
• * Have limited lifetime use of hallucinogens (the following criteria are preferred: no use in the past 2 years; total hallucinogen use less than 10 times)
• * Have at least a high school level of education or equivalent (e.g. GED).
• * Weigh between 40kg - 120kg.
• * (for female participants) Agree to use highly effective birth control measure within two weeks of completing the dosing sessions.