The present thesis investigates the association between violent crime and schizophre-nia. Research literature, clinicians and the public seem to have mixed and often contra-dicting opinions on whether and why individuals with schizophrenia are at elevated risk of violent criminal offending. Therefore, this thesis is written with the overall aim of advancing knowledge of violent criminal offending among individuals with schizo-phrenia. This may lead to enhanced methods for the prevention of violent criminal of-fending and, hopefully to the reduction of stigmatisation and public fear of people with schizophrenia.
A systematic review design was used throughout this thesis to search bibliographic databases and reference lists from 1970 to March 2018. Included are studies that report on risks of violent crime in individuals with schizophrenia compared with general pop-ulation samples. After applying a set of inclusion- and exclusion criteria, nine individu-al studies were identified reporting data from 20.550 individuals with schizophrenia. The data were synthesised by using a meta-analysis and all odds ratios were pooled using the random-effects model. Furthermore, the additional data, which was not appli-cable for meta-analytic synthesising, is included in a discussion to further the under-standing of the association
The systematic review and meta-analysis finds that the odds ratios for violent crime in those with schizophrenia compared to those without vary from 1,8 to 6,4 with substan-tial heterogeneity. It was considered whether or not to include the pooled odds ratio for the combined meta-analysis, given that the estimation might be affected by the hetero-geneity and the presence of publication bias. With this consideration in mind, at last, it was decided to include the pooled results. Therefore, the overall odds ratio indicates that people with schizophrenia have a fourfold risk of violent criminal offending com-pared to the general population.
The discussion of the results suggests that although schizophrenia is associated with an increased risk of violent criminal offending, this association appears to be mediated by a number of confounders. Firstly, the risk factors for violent criminal offending present in childhood or early adulthood are found to be similar for individuals with schizo-phrenia as compared to the general population, specifically low socioeconomic status and the presence of conduct disorder in childhood and adolescence. Secondly, all of the included studies report that substance abuse comorbidity is a substantial risk factor, thus this should be investigated further. Lastly, the symptomatology of schizophrenia or more specifically the psychotic symptoms, might be contributing to the increased risk.
Although violence associated with schizophrenia is significantly higher than that ob-served among the general population, the absolute amount of violent crime committed by these individuals is still low. Moreover, the percentage of individuals with schizo-phrenia who engage in violent behaviour is also low and it is not clear in the research literature which types of violent crime individuals with schizophrenia are more likely to commit. If these results are not reported the majority, who are not violent are left with discrimination and stigmatisation.