Objective: The impact of substance abuse on violent behavior in patients suffering from schizophrenia is well-known. However, the association between the pattern of substance abuse and certain aspects of criminal behavior like the severity of offense, the previous history of violence and the age at onset of the criminal career is still unclear.
Method: To assess the relationship between substance abuse, schizophrenia and violent behavior we examined healthy non-offenders; healthy offenders; non-offenders suffering from schizophrenia; and offenders suffering from schizophrenia, with respect to different patterns of substance abuse (none, alcohol only, illicit drugs only, and multiple substances).
Results: Healthy offenders as well as offenders and non-offenders suffering from schizophrenia are characterized by increased rates of alcohol and illicit drug abuse. Especially multiple substance abuse appears to lower the threshold of aggression and illegal behavior. This effect is more pronounced in subjects suffering from schizophrenia. In both offender groups the abuse of psychoactive substances is associated with an earlier onset of the criminal career, but has no impact on the severity of the offenses.
Conclusion: Our results point to the need for a differentiated view on the contribution of substance abuse to the criminality of subjects suffering from schizophrenia.
Keywords: schizophrenia, substance abuse, alcohol, illicit drugs, criminal behavior, violence