Substance abuse and psychosis. The strange case of opioids.
Psychoses correlated with substance abuse prove to be more common in cases involving cannabinoids, stimulants, hallucinogens, alcohol and polyabuse. Among substance abusers, it has not been ascertained whether opioids have a psychotic effect. The aim of this review is to investigate whether, among substances of abuse, a distinction can be drawn between pro-psychotic and anti-psychotic agents on the basis of the relationship between these substances and psychosis. Studies were identified by searching through multiple literature databases, including PubMed, Scopus, Web of Knowledge. Hand searches through reference lists of relevant reviews were used to complement the computer searches. Looking at the relationships linking substances of abuse with psychosis, a distinction can, in fact, be drawn between pro-psychotic and anti-psychotic substances. Even if there are no differences in the addictive processes involved, opiates are the only sedative drugs that possess an anti-psychotic effect. The whole topic of opiate agonism merits is due for reconsideration it is not only the anticraving action of opiate agonism, but also its effectiveness on the psychopathological level that qualifies it as to be viewed as a powerful tool in treating mental illness.