Psilocybin and Addiction
"The results of the present study have implications for understanding the abuse of hallucinogens. Although psilocybin is regulated by the federal government under the most restrictive category (Schedule I) of the Controlled Substances Act, the National Institute on Drug Abuse (2001, 2005) does not consider psilocybin and the other classical hallucinogens to be drugs of 'addiction' because they do not produce compulsive drug-seeking behavior as do classic addicting drugs such as cocaine, amphetamine, heroin, and alcohol. This conclusion is consistent with observations that psilocybin and other classic hallucinogens do not maintain reliable drug self-administration in animal laboratory models of drug abuse (Griffiths et al. 1980; Fantegrossi et al. 2004) and that most recreational users of classical hallucinogens decrease or stop their use over time (National Institute on Drug Abuse 2001). In the present study, psilocybin did not produce a classic euphorigenic profile of effects: measures of anxiety and dysphoria (monitor ratings of anxiety: AIA scale on the APZ Questionnaire, LSD scale on the ARCI) were significantly greater after psilocybin than after methylphenidate"
Griffiths, R. R.; Richards, W. A.; McCann, U.; Jesse, R., " Psilocybin can occasion mystical-type experiences having substantial and sustained personal meaning and spiritual significance,"Psychopharmacology (Heidelberg, Germany: August 2006), Volume 187, Number 3, p. 281.