Treatment of substance abuse in mentally ill patients may lessen the risk of future violence, according to a recent study.

Researchers from the University of Buffalo Research Institute on Addictions found that reducing substance abuse has a greater influence in reducing violent acts by patients with severe mental illness than improving their mental health.

"We were surprised to find that the severity of the patient's psychiatric symptoms was not the primary factor in predicting later aggression," Clara Bradizza, senior research scientist at RIA and co-author of the study, said in a statement. "Rather, the patient's substance abuse was the factor most closely associated with future aggression."

Although the vast majority of people with mental illness do not engage in violent acts, the risk of violence is greater among the severely mentally ill than among the general population, and the connection between severe mental illness, substance abuse and aggression is a significant concern for community safety, treatment programs and public policy.

For the study, researchers followed nearly 300 patients over a six-month period following admission to an outpatient dual-diagnosis treatment program that provided both substance abuse and mental illness treatment.

"Our findings suggest that treatment attendance is very important for these individuals and treatment programs should include interventions that are likely to decrease substance abuse, as this may provide the additional benefit of reducing the risk of later aggression among dual-diagnosis patients," Bradizza said. "This not only improves the lives of affected individuals and their families, but also provides a safer environment for society as a whole."

The findings were published in the current online edition of the Journal of Substance Abuse Treatment.