Severe Mental Illness and Risk of Sexual Offending in Men: A Case-Control Study Based on Swedish National Registers

Objective: To examine the comorbidity of severe mental illness with sexual offending in men.

Method: A case-control design was used to investigate psychiatric hospitalization and sexual offending. Data were obtained from Swedish national registers for crime, hospital discharge diagnoses (based on International Classification of Diseases revisions 9 and 10), demographic, and socioeconomic factors for the years 1988 through 2000. All male sexual offenders (N = 8495) in Sweden were included and compared with a random sample of male controls taken from the general population (N = 19,935). The population attributable risk fraction (the proportion of all sexual crimes throughout the study period that were committed by patients with a history of psychiatric hospitalization) was also estimated.

Results: After adjustment for demographic and socioeconomic confounders, sexual offenders were 6 times more likely to have a history of psychiatric hospitalization compared with the general population (OR = 6.3, 95% CI = 5.7 to 6.9). Sexual offenders were significantly more likely to have a severe mental illness than the general population, whether this was schizophrenia (OR = 4.8, 95% CI = 3.4 to 6.7), other psychoses (OR = 5.2, 95% CI = 3.9 to 6.8), or bipolar affective disorder (OR = 3.4, 95% CI = 1.8 to 6.4). The proportion of all sexual crimes committed by hospitalized psychiatric patients (the population attributable risk fraction) was 20.1%.

Conclusion: The increased relative risk of psychiatric hospitalization and severe mental illness in sexual offenders is contrary to much expert opinion in the field. If these findings are replicated in other settings, policies in the criminal justice system regarding the assessment, management, and treatment of sexual offenders may need review.