Patients who have been prescribed mood stabilizers or antipsychotic medications for mental illness symptoms are less likely to be convicted of violent crimes when they are taking their medications than when they are not, according to British and Swedish researchers.
That may seem obvious, but while there is already good evidence for the value of those drugs in preventing relapse and relieving psychiatric symptoms, “evidence about the effects of pharmacotherapy on other important outcomes, including violent behavior, is scarce,” wrote Seena Fazel, M.D., a Wellcome Trust Senior Research Fellow and an honorary consultant forensic psychiatrist at the University of Oxford, in England, and colleagues online May 8 in The Lancet.
“This is another piece of evidence that treatment works and that it’s important to get people connected with psychiatric services,” commented Marvin Swartz, M.D., a professor of psychiatry and behavioral sciences at Duke University, who was not involved with Fazel’s study.
The researchers looked at linked national population, medical, and criminal registers in Sweden to collect data on 82,647 patients who were prescribed the medications from 2006 to 2009. They adopted a within-individual approach, comparing rates of violent crime in the same person when that individual was on and off the medication. During the study, 3,261 of the patients were convicted of violent crimes.
Violent crime fell by 45 percent when patients were taking their antipsychotic medications and by 24 percent when taking a mood stabilizer, reported Fazel. A nonsignificant reduction in crime also occurred among those talking clozapine, but use of selective serotonin reuptake inhibitors did not affect rates of criminal convictions.
The difference in risk of committing a violent crime was similar regardless of whether a treated patient stopped taking medication or an untreated one started. Greater reductions in crime were associated with higher dosages of antipsychotics but not with the dosages of mood stabilizers or clozapine.
Despite having been prescribed antipsychotics or mood stabilizers, only about 40 percent of the patients in the study had been diagnosed with schizophrenia, other psychoses, or bipolar disorder, noted Fazel and colleagues
“Nevertheless, the consistency of our findings across diagnostic boundaries suggests the mechanism of the antipsychotic action in risk reduction might not only include psychotic symptoms, but also behavioral traits of anger and hostility.”
Swartz noted that there are many pathways to violent crime and offered several possible explanations of why being treated with these medications may lessen violent crime.
“It could be that the drug might make a person less aggressive or less impulsive or might treat some other underlying condition,” he suggested in an interview with Psychiatric News. “Or perhaps they are not using substances when they are taking their medications.” Substance use coupled with mental illness has been shown in several studies to be more strongly associated with violence than the presence of mental illness alone.
There may be an element of reverse causation that accounts for some of the effects shown in the study, Swartz added. “Perhaps people taking the drugs are more tractable, more ready to change their lives and so less likely to commit crimes,” he said. “But these are not mutually exclusive explanations.”
Other processes might be at work, Fazel also acknowledged. “Antipsychotic or mood-stabilizing medication might lead to nonpharmacological benefits, such as more regular contact with health care staff, psychological interventions, or support from family and [caregivers].”
Patients of both sexes benefited from antipsychotic treatment when they were diagnosed with a psychotic disorder, but crime declined only among men taking a mood stabilizer, not among women, the researchers pointed out. Finally, crime decreased when an antipsychotic was added to a mood stabilizer but not when the reverse occurred. Depot antipsychotic formulations worked as well as oral drugs.
Aside from the higher adherence implied by the use of depot medications, the physician is alerted if patients do not show up for their next injection and can mobilize resources to find these patients and get them back on their regimen, said Swartz.
“[The] potential effects [of these drugs] on violence and crime should also be taken into account in decisions about management for these groups of patients,” concluded Fazel and colleagues. ■