People taking drugs for psychiatric problems like schizophrenia and bipolar disorder are less likely to commit a violent crime compared to when they are not on the drugs, a new study has found.
Those taking antipsychotic medication to treat psychiatric illness are 45% less likely to commit a violent crime compared to when they are not using the drugs, researchers from Oxford University and the Karolinska Institutet in Sweden have found.
The use of mood stabilising drugs is also associated with a reduced rate of violent crime, although the reduction is less pronounced and only seen in men with bipolar disorder.
'Patients with psychiatric disorders are at risk of perpetrating violent acts, as well as being victims,' says lead author Dr Seena Fazel of Oxford University's Department of Psychiatry. 'Until now, we have not known whether antipsychotics and mood stabilizers reduce risks of violence. By comparing the same people when they are on medication compared to when they are not, our study provides evidence of potentially substantial reductions in risk of violence, and suggests that violence is to a large extent preventable in patients with psychiatric disorders.'
The researchers used Swedish national health registries to study psychiatric diagnoses and any subsequent criminal convictions in over 80,000 patients prescribed antipsychotic or mood stabilising drugs from 2006 to 2009.
They have published their findings in the medical journal The Lancet.
Antipsychotic medication (such as clozapine or risperidone) and mood stabilising drugs (such as lithium or carbamazepine) are used to treat a variety of mental health conditions. But they are most commonly used to treat schizophrenia, bipolar disorder, and related disorders that affect up to 2% of the general population.
Previous studies have found that people prescribed these drugs are less likely to relapse or be readmitted to hospital for their illness. However, until now there has been very little evidence for these drugs' effects on real-world outcomes beyond symptom relief – outcomes such as reducing violent behaviour. This is despite increasing prescription rates in many countries.
Commenting on the study in a separate article in the Lancet, Professor Sheilagh Hodgins of the Université de Montréal in Canada and Karolinska Institutet writes that: '[This] well executed study provides a basis for future clinical studies aiming to establish how antipsychotics and mood stabilisers can be used to reduce aggressive behaviour. The study illustrates again that de-identified data from national registers that were established for administrative reasons can be used by epidemiologists to identify potential strategies to reduce health-related social problems.'
The study was funded by The Wellcome Trust, the Swedish Prison and Probation Service, the Swedish Research Council, and the Swedish Research Council for Health, Working Life and Welfare.