Background: The aim of this study was to investigate whether 'dual diagnosis' (substance misuse and severe mental illness) is associated with aggression and offending.
Method: Twenty-seven people meeting the criteria for both psychotic illness and a substance use disorder and 65 people with psychosis only were interviewed. Case notes were also examined and keyworkers asked to rate substance misuse and aggression.
Results: The severity of aggression and offending among this community treatment sample was low. Individuals with a dual diagnosis were significantly more likely than those with psychosis only to report any history of committing an offence (P = 0.001), or recent hostile behaviour (P = 0.001). Keyworkers were more likely to report recent aggression among the dually diagnosed (P = 0.01). Significant differences persisted when we used logistic regression to control for potentially confounding demographic and clinical variables.
Conclusions: Dual diagnosis may be an important factor in aggression and offending among severely mentally ill individuals in inner-city areas. Accurate risk assessment requires examination of substance use.