Possible Induction of Mania and Hypomania by Olanzapine or Risperidone: A Critical Review of Reported Cases

Background: Risperidone and olanzapine areatypical antipsychotics that are now widely used in clinicalpractice.

Method: A MEDLINE search (1966-1999) showedthat, following the introduction of these agents in recent years,26 cases of induced hypomanic and manic syndromes have beenreported during standard olanzapine (N = 10) or risperidone (N =16) treatment.

Results: A critical analysis of these casereports reveals that the effects on mood were sometimesinsufficiently documented and that in about half of them (N = 16)evidence is highly suggestive of a causative role of risperidoneor olanzapine in the induction of (hypo)manic symptomatology.

Conclusion: Despite limitations, the availableliterature confirms intriguing effects of these 2 antipsychoticson mood. The risk factors as well as the mechanisms of actionunderlying these effects remain to be clarified.