To evaluate the effectiveness of NGAs, in particular olanzapine and risperidone, in treating aggressive behaviour in PWID for who previous medication with First Generation Antipsychotics (FGAs) were not effective.

62 subjects with intellectual disability underwent to a two-arm, parallel group pragmatic trial of olanzapine and risperidone with balanced randomisation and blind assessment of outcomes after a switch from a treatment with FGAs. Psychiatric disorders were evaluated by Diagnostic Assessment for the Severely Handicapped (DASH). Aggressive behaviour was assessed by Overt Aggression Scale (OAS) and clinical outcome by Clinical Global Impression (CGI) Scale. Side effects were assessed with specific scales, laboratory and instrumental tests.

Both risperidone and olanzapine resulted to be more effective than FGas in reducing aggressive behavior and in treating concurrent psychiatric disorders. the degree of improvement in our sample was very high for OAS and CGI scores. Both compounds resulted to be well tolerated, with side-effects similar to those encountered in other patient populations.

Our findings seem to confirm previous literature on that olanzapine and risperidone can be effective in reducing aggressive behaviour in PWID. Although NGas have shown greater efficacy and safety than FGAs, there is still a need for controlled trial and more methodically researches to confirm their benefit.