Mental illness and the risk of self- and other-directed aggression: Results from the National Survey on Drug Use and Health.

Aggression and mental illness have been classically interlinked, often causing controversy and debate. Previous studies have shown that mental illness can be a risk factor to self- and other-directed aggression. However, these associations have rarely been simultaneously studied within the same population. Therefore, we aimed to study whether psychiatric disorders differentially increase the likelihood of one subtype of aggression over the other. We used the publicly available data of the National Survey on Drug Use and Health (NSDUH) from 2008 through 2014, for a total sample of 270,227 adult respondents. We designed our independent variable according to three categories: no mental illness (NMI), low or moderate (LMMI) and serious (SMI). We constructed regression models to estimate the odds ratios for those having a mental illness committing (a) a subtype of aggression over the past year compared with no aggression and (b) other-directed compared to self-directed aggression. We found that most respondents with mental illness reported no past-year aggression of any type. However, respondents with mental illness had higher odds of perpetrating all subtypes of aggression. Additionally, respondents with LMMI and SMI were respectively 1.7 and 3 times more likely to engage in self- rather than other-directed aggression. Future research should focus on identifying accurate and reliable predictors of self- and other-directed aggression among individuals with mental illness.