Severe mental illness trumps PCL-R and HCR-20: Commentary on Simpson et al.

In the current issue of this journal, Simpson et al. (2015) examine a series of 232 forensic patients from Toronto, most of whom have schizophrenia or a related psychosis, and propose a typology based on the age of onset of mental illness compared to the index offence. All of the offenders were found to be unfit to stand trial or not criminally responsible for their actions because of the severity of mental illness. A quarter of the offenders had committed serious violent offences, including homicide, attempted murder and aggravated assault.

Although the study population is defined by the presence of a severe mental illness, the analysis mainly considers the criminological characteristics of the sample, and does not directly examine clinical variables, for example, intellectual function of the pattern of symptoms or treatment. The study does report the scores on a scale to estimate the probability of future violence (Historical Clinical Risk Management–20, HCR-20), and the clinical items on the HCR-20 include lack of insight, active symptoms and lack of response to treatment. The authors also report the average scores on the Psychopathy Checklist–Revised (PCL-R), a scale to measure antisocial attitudes and behaviours, on the basis that it has ‘excellent reliability and validity for future violence and delinquency’. However, the PCL-R is probably not a valid measure in people with severe mental illness, given the impairment in social skills and impulse control often associated with disabling psychotic illness. In any case, the reported mean PCL-R scores were relatively low when compared to other offender populations.

The study observed that around a quarter of the sample had a criminal career averaging more than 10 years and more than 10 convictions before they were found to be not criminally responsible or unfit to stand trial. This finding raises the question of how those earlier offences were dealt with by the courts, and whether there was a progression in the severity of mental illness, or in the seriousness of the offences. The characteristics of that sub-sample with a long criminal history were comparable to a series of serious non-lethal violent offenders (Yee et al., 2011), which found a relatively small proportion (16%) of the psychotic offenders had been diagnosed with psychosis for the first time, a mean age of first conviction several years before the diagnosis of mental illness and high rates of substance use and other criminological risk factors.

The analysis by Simpson et al. differs from the approach taken in other recent studies, for example, case linkage studies that compare the dates of onset of criminal offending with the dates of first contact with mental health services (e.g. Munkner et al., 2003), which found the majority of initial offending in people subsequently found to have schizophrenia took place immediately before the diagnosis. The analysis also departs from the findings of studies of phase of illness at the time of serious violent offences due to mental illness (e.g. Nielssen et al., 2012), which show that about half of the most serious offences by the mentally ill were committed prior to initial treatment, often after a long duration of untreated psychosis.

Simpson et al. describe another group of forensic patients with a relatively late onset of illness, and with few or no offences prior to the index offence. It would have been of considerable interest to know whether a proportion of those offenders presented for treatment for the first time by committing an offence, and whether they also had a long duration of untreated illness, because reducing the duration of untreated psychosis and assertive treatment of first episode psychosis might prevent some episodes of serious violence and self-harm.

As well as being of limited use in formulating policies to reduce violence by the mentally ill, it is also difficult to see how the typology devised by Simpson et al. would be of any value to the Ontario Review Board, or any similar authority, in deciding whether to release a forensic patient. Decisions to release forensic patients almost invariably turn on the response to treatment and the advice about the arrangements made for support and supervision after release. Release decisions have to be made regardless of the patient’s scores on the HCR-20 and PCL-R, as those scores tend to be fixed, whereas the course of serious mental illness is often permanently changed by a period of adequate treatment and participation in rehabilitation programmes. We do know from Simpson’s earlier work in New Zealand and a recent study from NSW (Hayes et al., 2014) that released forensic patients have low rates of re-offending, including patients with long criminal histories. This suggests that for people who have committed offences while seriously mentally ill, the individual’s circumstances and response to treatment are more important than historical factors in deciding on the conditions of release.

See Research by Simpson et al., 49(11): 1048–1059.