This study will investigate the effects of psilocybin dose and the frequency and intensity of support activities for spiritual practice (e.g., meditation) on a battery of attitudinal and behavioral outcome measures in 75 healthy volunteers who are interested in pursuing a program of spiritual practices with the intention applying spiritual insights and knowledge to everyday life. After screening and study enrollment, each volunteer will be assigned to one of five groups that vary in dose, frequency and intensity of support for spiritual practice, and number of psilocybin sessions (either 2 or 3 sessions). The psilocybin dose manipulation will be double-blind. Volunteers will be told that in each of sessions 1, 2, and 3, he/she could receive a very low, low, moderate, moderately high, or high dose of psilocybin. They will be told that each participant will receive 2 or more dose levels of psilocybin over the 2 or 3 sessions, and all participants will have one or more sessions in which he or she receives a moderately high or high dose of psilocybin. The duration of each volunteer's participation will be approximately 6 to 8 months. Each volunteer will receive several hours of preparation with the study guides in the month prior to the first psilocybin session; the first two sessions will be separated by one month. Various measures will be assessed before, during and immediately after sessions. A battery of longitudinal measures will be evaluated immediately after study enrollment, 3 weeks after the second psilocybin session, and 4 months after the second psilocybin session (6 months after study enrollment). For purposes of controlling expectancies through the 6 month follow-up evaluation, volunteers and guides will not know which volunteers or how many volunteers will be scheduled for a third session.

Eligibility criteria for volunteers who will receive psilocybin

Inclusion Criteria:

• 21 to 70 years old
• Have given written informed consent
• Have a high school level of education
• Be healthy and psychologically stable as determined by screening for medical and psychiatric problems via a personal interview, a medical questionnaire, a physical examination, an electrocardiogram (ECG), and routine medical blood and urinalysis laboratory tests.
• Have an active interest in exploring and developing their spiritual lives
• Cigarette smokers must agree to abstain from smoking on psilocybin session days from 1 hour before psilocybin administration until at least 6 hours after psilocybin administration.
• 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 volunteer does not routinely consume caffeinated beverages, he or 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 psilocybin administration. Exceptions include caffeine and nicotine.
• Agree not to take any PRN medications on the mornings of psilocybin sessions
• Agree that for one week before each psilocybin 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.

Exclusion Criteria:

General medical exclusion criteria:

• Women who are pregnant (as indicated by a positive urine pregnancy test assessed at intake and before each drug session) or nursing; women who are of child-bearing potential and sexually active who are not practicing an effective means of birth control
• Cardiovascular conditions: coronary artery disease, stroke, angina, uncontrolled hypertension, a clinically significant ECG abnormality (e.g., atrial fibrillation), or TIA in the past year
• Epilepsy with history of seizures
• Insulin-dependent diabetes; if taking oral hypoglycemic agent, then no history of hypoglycemia
• Currently taking psychoactive prescription medication on a regular (e.g., daily) basis
• Currently taking on a regular (e.g., daily) basis any medications having a primary centrally-acting pharmacological effect on serotonin neurons or medications that are MAO inhibitors. For individuals who have intermittent or PRN use of such medications, psilocybin sessions will not be conducted until at least 5 half-lives of the agent have elapsed after the last dose.
• More than 20% outside the upper or lower range of ideal body weight

Psychiatric Exclusion Criteria:

• Current or past history of meeting DSM-IV criteria for Schizophrenia, Psychotic Disorder (unless substance-induced or due to a medical condition), or Bipolar I or II Disorder.
• Current or past history within the last 5 years of meeting DSM-IV criteria for alcohol or drug dependence (excluding caffeine and nicotine) or severe major depression.
• Have a first or second degree relative with Schizophrenia, Psychotic Disorder (unless substance induced or due to a medical condition), or Bipolar I or II Disorder.
• Currently meets DSM-IV criteria for Anorexia Nervosa, Bulimia Nervosa, or other psychiatric conditions judged to be incompatible with establishment of rapport or safe exposure to psilocybin