Risperidone and olanzapine in adults with intellectual disability: a clinical naturalistic study

Atypical antipsychotics are the first-line treatment for psychosis and are commonly used for behavioural problems in people with intellectual disabilities (ID), but a comprehensive evidence base for this approach is lacking. We studied prescription trends and the clinical effectiveness of risperidone and olanzapine in people with ID in a clinical, naturalistic setting. The results suggest that both drugs are well tolerated and effective in treating target symptoms across a range of diagnoses and ID. Both risperidone and olanzapine appear to reach full efficacy within 3 months, after which improvement reaches a plateau, as reflected in the Clinical Global Impression-Improvement scale. Compliance with both drugs is high. Olanzapine tended to be prescribed mostly for psychotic disorders, and showed good rates of response, whereas risperidone was prescribed mostly for people with behavioural disturbance associated with a psychiatric diagnosis. Furthermore, approximately one-quarter of the risperidone group were prescribed the medication for a behavioural disorder associated with a pervasive developmental disorder. Again, the medication was broadly effective in treatment. Both medications were also used to effectively treat affective disorders in a small percentage of patients. This study appears to indicate that both medications could be of significant clinical benefit for people with ID across a wide range of diagnoses and level of ID, although further controlled trials are required.