There are very few comparative controlled trials of risperidone versus olanzapine in manic patients. No previous naturalistic study has compared the efficacy of these two antipsychotics in the natural environment of manic inpatients.

The aim of this retrospective and naturalistic study was to evaluate the efficacy of acute treatment with risperidone vs. olanzapine in Bipolar I manic inpatients.

(1) Patients: the study includes all the inpatients diagnosed with bipolar I manic episode (DSM-IV) who were admitted during the years 2009 to 2014. Patients treated with risperidone and olanzapine concomitantly (n = 6) and patients not treated with risperidone or olanzapine (n = 129) were excluded.

The patients finally included (n = 183) were separated in two groups:

– treated with risperidone (n = 89);

– treated with olanzapine (n = 94).

(2) The Student-T test was used to compare, between the groups, the mean of scores in YMRS and CGI-S scales and the mean of length of stay.

Baseline characteristics were similar between the groups. The majority of patients were also treated with mood stabilizers (46% with lithium and 45% with valproate).

The mean decrease in CGI-S scores from baseline to the day of discharge was significantly (P < 0.003) higher in the risperidone group (−2.81 vs. −2.36). The length of stay was significantly (P < 0.004) lower in the olanzapine group (mean of 23.03 days vs. mean of 30.3).

(1) The CGI-S scores in manic patients treated with risperidone decreased more than in patients treated with olanzapine during admission. (2) The length of stay was significantly lower in patients treated with olanzapine.

The authors have not supplied their declaration of competing interest.