Concord Prison Experiment
The experiment was conducted between 1960–1963 in Concord State Prison, a maximum-security prison for young offenders, in Concord, Massachusetts by a team of Harvard University researchers under the direction of Timothy Leary, which included Michael Hollingshead and Allan Cohen, Alfred Alschuder, George Litwin, Ralph Metzner, Gunther Weil, and Ralph Schwitzgebel, with Madison Presnell as the medical and psychiatric adviser. The original study involved the administration of psilocybin to assist group psychotherapy for 32 prisoners in an effort to reduce recidivism rates.
Records at Concord State Prison suggested that 64 percent of the 32 subjects would return to prison within six months of parole. However, after six months, only 25 percent of those on parole had returned, six for technical parole violations and two for new offenses. Few short-term projects with prisoners have been effective to even a minor degree. In addition, the personality test scores indicated a measurable positive change when pre-psilocybin and post-psilocybin results were compared.
The results of this experiment have been largely contested by a follow-up study, citing several problems including differences in the length of time after release that the study group versus the control group were compared, and other methodology factors including the difference between subjects re-incarcerated for parole violations versus imprisoned for new crimes. This study concluded that only a statistically slight improvement could be shown (as opposed to the radical improvement originally reported). In his interview within the study, Leary expressed that the major lesson of the Concord Prison experiment was that the key to a long-term reduction in overall recidivism rates might be the combination of the pre-release administration of psilocybin-assisted group psychotherapy with a comprehensive post-release follow-up program modeled on Alcoholics Anonymous groups to offer support to the released prisoners. The study concluded that whether a new program of psilocybin-assisted group psychotherapy and post-release programs would significantly reduce recidivism rates is an empirical question that deserves to be addressed within the context of a new experiment.
Study by researchers from the University of Alabama at Birmingham and Johns Hopkins University School of Medicine collected data on 25,622 individuals under community corrections supervision in Treatment Accountability for Safer Communities and found that hallucinogen use predicted a reduced likelihood to fail the TASC program. Results suggest that hallucinogens may promote alcohol and other drug abstinence and prosocial behavior in a population with high rates of recidivism.