THE RISK of violent offending has been estimated to be several times higher in people with mental illness.
Exploring this claim further, scientists from the University of Western Australia’s (UWA) School of Psychiatry and Clinical Neurosciences and Crime Research Centre have recently completed an epidemiological whole-population longitudinal study assessing patterns of offending across psychiatric and non-psychiatric populations.
According to UWA Professor Vera Morgan the mean percentage of annual change in the number of arrests in 1985-1996 rose significantly for offenders with a psychiatric illness and dropped significantly for those with no mental illness.
However, the research found the highest arrest prevalence was most evident in people with substance abuse disorders – rating three out of five arrested.
Prof Morgan and her research team used a study cohort of Western Australians born from 1955-1969 and those arrested between 1985-1996.
“In this epidemiological study we look at patterns of criminal offending in relation to whether a person had a mental illness or not across a whole population over a substantial period of time,” says Prof Morgan.
Of the study cohort 116,656 people had been arrested and 40,478 were on the psychiatric case register.
This equates to 32.1 per cent of people with a recorded psychiatric illness having an arrest.
One in 10 offenders had a history of psychiatric illness.
This rose to one in five violent offenders having a psychiatric illness.
Male offenders registered significantly higher than female.
Personality disorders equated to 35.9 per cent while schizophrenia had an arrest prevalence of 38.7 per cent.
Co-morbid substance abuse disorder increased the risk of violent offending in people with schizophrenia.
However, people diagnosed solely with schizophrenia showed no definitive pattern over time of increased offending.
“A peak occurred early in the 1990s [which] possibly related to the relocation of patients with schizophrenia from hospitals to the community before proper resources were in place,” Prof Morgan says.
First arrest often preceded first contact with mental health services.
“An arrest may be the result of changes in behaviour in the early stages of a psychotic illness,” says Prof Morgan.
“It may bring a person to the attention of authorities and their illness finally identified by mental health services.
“With correct diagnosis; medication and other treatments can be started and a mental health plan put into place.”
Conclusively arrests for offenders with a psychiatric illness increased over time and dropped for those with no mental illness.
The research highlights the role of substance abuse as a key risk factor for criminal offending, especially when co-occurring with mental illnesses such as schizophrenia.
“It is imperative for well-designed epidemiological studies to provide a rational basis for understanding the association between criminal offending and mental illness,” says Prof Morgan.