Low crime rate among mentally ill patients in Hong Kong

Researchers at the Castle Peak Hospital and Queen Mary Hospital have shown in a 10-year retrospective review study that the estimated crime rate for mentally ill patients and estimated prevalence of mental disorders among prisoners are relatively low in Hong Kong.

A total of 7,535 incarcerated offenders (male, 74.8 percent; mean age at admission, 41.3 years) who were referred to and seen by psychiatrists at the Siu Lam Psychiatric Centre (SLPC) from 1 January 2011 to 31 December 2020 were included in the study. “The results of this study are believed to be representative as SLPC is the only correctional facility purpose-built in Hong Kong for mentally ill offenders,” said the researchers. [Asia Pac Psychiatry 2021;doi:10.1111/appy.12505]

The study showed that the estimated prevalence of mental illness among incarcerated offenders was 7.1 percent – slightly lower than the global figures – with a higher prevalence among male offenders (8.2 percent) than female offenders (5.0 percent).

The estimated yearly crime rate for mentally ill patients was 43.3–263.2 per 100,000 population, which was lower than the average overall yearly crime rate of 453.0 per 100,000 population for the general population in Hong Kong, suggesting that mentally ill patients may not be as offensive as perceived by the general public.

In SLPC, the three most common psychiatric diagnoses were schizophrenia and related disorders (22.8 percent), mental and behaviour disorders due to psychoactive substance use (18.6 percent), and mood disorders (8.8 percent).

Among the offenders seen at SLPC, the three most common offences were theft and related offences (20.5 percent), acts intended to cause injury (19.7 percent), and illicit drug offences (11.6 percent). When the prevalence rate from the Hong Kong Mental Morbidity Survey (HKMMS) was adopted, estimated yearly rates of all crimes among the mentally ill patients were lower than rates in the general population in Hong Kong, except for homicide and related offences, which were slightly higher in the mentally ill patients than the general population (0.6 vs 0.5 per 100,000 population).

Age was found to be a risk factor for violent offences only for offenders diagnosed with schizophrenia and related disorders (odds ratio, 1.96; 95 percent confidence interval, 1.22 to 3.16, p<0.01). Male gender was the only risk factor identified for violent offences for all mentally ill offenders. However, repeated incarceration was not associated with violent offences. Continued risk assessment and management should be in place to predict and manage the risk of violence among offenders.

“This is the first study that attempted to estimate the prevalence of mental illnesses among the incarcerated population in Hong Kong, and also the first study to compare the estimated crime rates of mentally ill patients with the overall crime rate in the Hong Kong population,” pointed out the researchers.

“While aggression is one of the dimensions for stigmatization of mentally ill patients, our results support that mental disorders alone are neither necessary nor sufficient causes of violent and nonviolent offences. Our findings may assist in alleviating the stigmatization for mentally ill patients in Hong Kong,” noted the researchers.