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.