Concerns about individuals with mental illnesses perpetrating violence have been greatly amplified since the 32 homicides at Virginia Tech in 2007. However, recent research into the relationship between mental illnesses and violence shows a complicated relationship. An epidemiological study involving several thousand individuals was completed in an attempt to tease-out the impact of mental illness on the risk of violent behavior.[i]
These researchers concluded that the relationship between severe mental illness alone and violence is not statistically significant. In other words, people suffering from a severe mental illness alone, without any other risk factors, were not at an increased risk of committing a violent act, and in fact, have the same chance of being violent as any other person in the general population during the next three years.[ii]
However, that being stated, the incidence of violence is higher for individuals with mental illnesses. How could that be? The incidence of violence is higher for individuals with mental illnesses because individuals with mental illnesses are more likely than the general population to also be associated with risk factors for violence and the combination of these other risk factors and mental illness lead to higher risks for violence than just the risk factor alone.
For example, “people with co-occurring mental illness and substance abuse and/or dependence had significantly higher incidence of violent acts” , and more than people with substance abuse alone. Further, 46% people with severe mental illness also had a lifetime history of substance abuse.[iii] Also, people with severe mental illnesses are more likely to have been victimized and prone to other environmental stressors, such as unemployment, which elevates the risk of violence.[iv]
These researchers stated that “the occurrence of 3 factors (severe mental illness, substance abuse and/or dependence, history of violence) was associated with a distinctly higher than average risk of violence.[v] The researchers concluded as follows” The current study aimed to clarify the link between mental disorder and violence, and the results provide empirical evidence that (1) severe mental illness is not a robust predictor of future violence, (2) people with co-occurring severe mental illness and substance abuse/dependence have a higher incidence of violence than people with substance abuse/dependence alone; (3) people with severe mental illness report histories and environmental stressors associated with elevated violence risk; and (4) severe mental illness alone is not an independent contributor to explaining variance in multivariate analyses of different types of violence….The data shows that it is simplistic as well as inaccurate to say the cause of violence among mentally ill individuals is the mental illness itself; instead, the current study finds that mental illness is clearly relevant to violence risk but that its causal roles are complex, indirect, and embedded in a web of other (and arguably more) important individual and situational cofactors to consider.”[vi]
[i] Elbogen, Eric B., and Sally C. Johnson, 2009, The Intricate Link Between Violence and Mental Disorder, Results from the National Epidemiologic Survey on Alcohol and Related Conditions, Arch. Gen. Psychiatry, 2009; 66(2):152-161.
[ii] Ibid. p. 157.
[iii] Ibid. p. 156.
[iv] Ibid. p. 156.
[v] Ibid p. 159
[vi] Ibid p. 159.