Schizophrenia and criminal offending : risk factors and the role of treatment

Abstract

Background: The present thesis is written with the overall aim of advancing knowledge of criminal offending among individuals with schizophrenia. This may lead to better and more cost-effective methods for the prevention of criminal offending and, hopefully, to the reduction of public fear of mentally disordered persons. One aim of the thesis was to study risk factors for criminal offending, specifically risk factors related to antisocial behaviour, low socioeconomic status, problematic substance use, and low intelligence. Another aim of the thesis was to study the role of treatment for the reduction of criminal offending.

Methods: A quantitative research design was used throughout the thesis. Papers I and II were based on data from The Comparative Study of the Prevention of Crime by Mentally Ill Persons (CSPCMIP), an international, multi-site follow-up study on forensic and general psychiatric patients in community care (N = 307). Papers III and IV were based on Swedish conscription data of 1969-1970 (N = 49 398; participants with a diagnosis of schizophrenia, n = 377) and follow-up data from the National Hospital Register and the National Crime Register. The participants of all four papers were males.

Results: Risk factors for criminal offending present in childhood or early adulthood were found to be similar for the participants with a diagnosis of schizophrenia as compared to the participants with no diagnosis of schizophrenia, specifically risk factors related to antisocial behaviour and problematic substance use (paper III). Associations were found between lower verbal intelligence and younger age of onset of non-violent criminal offending (paper I). A number of typologies of alcohol use disorder, including the well known Type I/II Type A/B typology, were replicated (paper II). No associations were found between inpatient psychiatric treatment and criminal offending (paper IV).

Conclusions: Criminal offending among individuals with schizophrenia shares many similarities with criminal offending among individuals with no mental disorder. It is a complex phenomenon with many factors involved from a macro to a micro level, some of them out of reach for psychiatric treatment efforts. It is suggested that criminal offending among individuals with schizophrenia should be studied within a common criminological framework. Methods and theories used in criminology may be of value for the field. Also, forensic psychiatric services may gain from adopting the what works approach from the correctional services.