Criminal offending before and after the onset of psychosis: examination of an offender typology.

OBJECTIVE: Clinicians often consider whether or not offenders with psychosis have a history of offending pre-dating the onset of their illness. The typology of offenders based on age at first offence, developed in the field of criminology, has been recently extended to mentally disordered groups, but this ignores the potential role of illness onset.

METHOD: Using a large UK cohort of individuals with both psychosis and offending histories (n=331), we compared those with a history of offending pre-dating their illness (pre-morbid offenders) to those who commenced offending after becoming unwell (post-morbid offenders). We compared the demographic, clinical and offending pattern characteristics of the two groups.

RESULTS: 198 (60%) had offended before the onset of psychosis. These pre-morbid offenders were more likely to be male, have a lower pre-morbid IQ and have had a history of neurological abnormality. Pre-morbid offenders also committed more crime overall, but this was due to an excess of acquisitive, drug and minor offending, rather than violent offending, which was comparable to the post-morbid offending group.

CONCLUSION: Currently, standardised clinical risk assessment tools view offenders with mental illness as a homogenous group with respect to life-course patterns of offending in relation to illness. Taking account of an individual's pathway to offending may improve risk assessment and management.