Psilocybin for the Treatment of Veterans With Post-Traumatic Stress Disorder

In order to be eligible to participate in this study, an individual must meet all of the following criteria:

* A US military Veteran
* 21 to 64 years old
* Have at least a high-school level of education or equivalent.
* Have a current DSM-5 diagnosis of Post-Traumatic Stress Disorder
* Have a CAPS-5 total severity score of ≥35 at baseline
* No antidepressant medications prior to enrollment
* Be judged by study team clinicians to be at low risk for suicidality
* Be medically stable
* Have limited lifetime use of hallucinogens

General medical exclusion criteria:

* Women who are pregnant
* Cardiovascular conditions
* Epilepsy with history of seizures
* Insulin-dependent diabetes
* Currently taking psychoactive prescription medication
* Currently taking on a regular (e.g., daily) basis any medications having a primary centrally-acting serotonergic effect, including Monoamine oxidase inhibitors..

Psychiatric Exclusion Criteria:

* Current or past history of schizophrenia or other psychotic disorders or Bipolar I or II Disorder
* Current or history within one year of a moderate or severe alcohol, tobacco, or other drug use disorder
* Have a first or second-degree relative with schizophrenia spectrum or other psychotic disorders or Bipolar I or II Disorder
* Has a psychiatric condition which precludes the establishment of therapeutic rapport
* History of a medically significant suicide attempt
* Current antidepressant use