A group of researchers from Johns Hopkins School of Medicine led by Griffiths conducted a study to assess the immediate and long-term psychological effects of the psilocybin experience, using a modified version of the mystical experience questionnaire and a rigorous double-blind procedure. When asked in an interview about the similarity of his work with Leary's, Griffiths explained the difference: "We are conducting rigorous, systematic research with psilocybin under carefully monitored conditions, a route which Dr. Leary abandoned in the early 1960s." The National Institute of Drug Abuse-funded study, published in 2006, has been praised by experts for the soundness of its experimental design. In the experiment, 36 volunteers without prior experience with hallucinogens were given psilocybin and methylphenidate (Ritalin) in separate sessions; the methylphenidate sessions served as a control and psychoactive placebo. The degree of mystical experience was measured using a questionnaire developed by Ralph W. Hood; 61% of subjects reported a "complete mystical experience" after their psilocybin session, while only 13% reported such an outcome after their experience with methylphenidate. Two months after taking psilocybin, 79% of the participants reported moderately to greatly increased life satisfaction and sense of well-being. About 36% of participants also had a strong to extreme "experience of fear" or dysphoria (i.e., a "bad trip") at some point during the psilocybin session (which was not reported by any subject during the methylphenidate session); about one-third of these (13% of the total) reported that this dysphoria dominated the entire session. These negative effects were reported to be easily managed by the researchers and did not have a lasting negative effect on the subject's sense of well-being.