I have delved into this issue before, saying that psychiatrists (the missionaries) were torn between trying to normalise mental illness, and (the actuaries) admitting that some psychiatric illnesses have deleterious effects on behaviour, particularly an increase in violence.
Now there are startling new results from a large, representative sample of Norwegians, showing that the rate of violence is about 7 times higher in schizophrenics as compared to controls, and 3 times higher for those with bi-polar disorder.
Genetic and environmental determinants of violence risk in psychotic disorders: a multivariate quantitative genetic study of 1.8 million Swedish twins and siblings
Molecular Psychiatry advance online publication 15 December 2015; doi: 10.1038/mp.2015.184
A Sariaslan, H Larsson and S Fazel email@example.com
Advance online publication 15 December 2015
Amir Sariaslan, formerly at the Karolinska, and now with colleages at Oxford, is becoming known for delving into the large goldmine of Swedish epidemeolgy and coming up with sparkling nuggets.
These are startling figures, based on excellent and very large samples, showing very high levels of substance abuse for schizophrenia and bipolar disorder, and high rates of violence for both, but particularly schizophrenia. Women seem to get bipolar disorder, men schizophrenia. Immigrants are slightly over-represented in bipolar and over twice as likely to get schizophrenia, a commonly found pattern. Schizophrenia particularly damages employment prospects and marriage prospects.
We observed, for instance, that nearly one in four (23%) schizophrenia patients had ever been convicted of a violent crime, whereas the equivalent prevalence was 11% in patients diagnosed with bipolar disorder and 3% in controls.
Schizophrenia was a stronger predictor of violent crime (r=0.32) than bipolar disorder (r=0.23). Consistent with previous quantitative and molecular genetic studies demonstrating important pleiotropic effects between the examined phenotypes,13, 14, 15 we found that 67% of the correlation between schizophrenia and violent crime, and 51% of the correlation between bipolar disorder and violent crime was attributed to additive genetic influences that were shared between the psychotic disorders, substance misuse, and violent crime. This suggests that the increased risk for violence in these patient groups could largely be attributed to the same genetic factors that simultaneously increased their liabilities to substance misuse and to be diagnosed with the psychotic disorders in the first place. However, we additionally observed a novel finding in that the additive genetic influences that were unrelated to substance misuse explained approximately a fifth (21%) of the correlation with violent criminality in bipolar disorder but none of the same correlation in schizophrenia. In other words, we found support for the existence of disorder-specific genetic effects linking bipolar disorder (but not schizophrenia) to increased violence risk. This implies that aetiological models involving psychotic disorders should not only focus on genetic and environmental factors that are shared between the disorders but also on those factors that are unique to each disorder.
Once again, very little shows up for C, the shared variance of family life we used to think had such an influence.
Here are the two disorders on their own, showing high heritability together with substance abuse, something disorder specific for bi-polar, and unique disorder-specific variance for both.
The authors are circumspect about the implication of their findings. They observe: Clinically, these findings illustrate the importance of risk assessments that consider substance misuse comorbidity, integrated treatments for multiple adverse risks and strong collaborations between criminal justice, substance misuse and mental health services.
If nearly one in four schizophrenics are convicted of violent crime then both the problem and the solution are now much clearer. I had formerly believed what I had been told, which is that violence was so rare in psychosis that it could not be prevented, other than by restricting the freedom of a very large number of schizophrenic patients. These findings suggest that for every schizophrenic patient closely monitored for substance abuse and aggressive behaviour 3 patients will be mildly restricted, a very tolerable ratio. This, in my view, totally changes the Number Needed to Treat calculation in favour of close monitoring. We routinely suggest treatments where the numbers needed to treat are 10 or higher. So long as the coordinated treatment regime were properly managed, few interventions would be show such extraordinary returns on treatment.
I do not want to stigmatise psychiatrists who deal with schizophrenic patients, but they now have a different calculation to make, and new findings to discuss with secure ward hospital administrators and, most of all, legislators. There is a case for preventative medicine in psychosis. This is nothing to do with stigmatisation and a lot to do with evidence-led interventions.