Effects of Hallucinogens and Other Drugs on Mood and Performance

Inclusion Criteria: * Be 21 to 50 years old * Have given written informed consent * Have a high school level of education * Have a self-reported interest in psychedelic drugs and altered states of consciousness * Have used classic, serotonergic hallucinogens or dissociative anesthetic hallucinogens (e.g., LSD, psilocybin mushrooms, ayahuasca, ketamine, PCP) without untoward effects. Volunteers must report "liking" of psychedelic and psychedelic-like drugs and report having used hallucinogens at least 5 times in their lifetime and at least once within the last 2 years * 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 usually consume caffeinated beverages, he or she must agree not to do so on session days * Cigarette smokers must agree to abstain from smoking on session days from 1 hour before drug administration until at least 6 hours after drug administration * Agree to refrain from using any psychoactive drugs, including alcoholic beverages, within 24 hours of each drug administration. Exceptions include daily use of caffeine and nicotine. * Be healthy and psychologically 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 that for one week before each 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 * Agree not to take any PRN prescription medications on the mornings of the sessions * Be willing and able to participate 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, 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 severe obsessive-compulsive disorder, dysthymic disorder, or panic disorder. * Current, 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 dissociative disorder, anorexia nervosa, bulimia nervosa, or other psychiatric conditions judged to be incompatible with establishment of rapport or safe exposure to study compounds