Trajectories Of Offending In People With Psychotic Illness And Other Mental Disorders: A Population Study

Abstract Background Trajectory analysis has been used to study long-term patterns of offending and identify offending groups. Only few studies have explored patterns in people with psychotic illness and these were restricted to adult offenders. This study examines offending trajectories, and identifies risk factors, for people aged 10-26 with psychotic illness (PI) and other mental disorders (OMD) compared to those with no mental disorders (NMD). Methods This is a whole-population record-linkage study of 184,147 people born in Western Australia (WA) 1983-1991 using data from WA psychiatric case register, WA corrective services and other state-wide registers. Group-based trajectory modelling was used to identify offending trajectories. Results Four offender groups were identified for each mental health status (MHS) group: MHS groups had similar offending patterns, however PI had a lower proportion of individuals in the G1 group and later offending onset in the G3 group. Gender, indigenous status, substance use, childhood victimisation and parental offending were risk factors associated with group membership; for PI, childhood victimisation and parental offending were only significant in the G4 group. Conclusions Overall offending patterns and risk factors were similar for all MHS groups, however, some differences were observed for PI. Key messages To reduce offending in this population, interventions need to occur at an early age.