An updated systematic review that included published and unpublished data of quetiapine for acute bipolar depression has not been performed.

To review the efficacy and the tolerability of quetiapine, either as monotherapy or in combination, in the treatment of acute bipolar depression.

We included all randomized control trials (RCTs) comparing oral quetiapine with other treatments in bipolar I or II disorders. Published and unpublished randomized, controlled trials were identified using the Cochrane Central Register of Controlled Trials, MEDLINE, ISI Web of Science, CINAHL, PsycINFO, and ClinicalTrials.gov. The primary outcome was the average change in depressive score, such as the Montgomery-Asberg Depression Rating Scale (MADRS) in adults or the Children's Depression Rating Scale-Revised (CDRS-R) in child and adolescents.

Overall, 11 RCTs with 3,488 participants were included. There was a significant difference, favoring quetiapine, in the change score of the MADRS (MD −4.66 CI −5.59 to -3.73). Quetiapine was also associated with significant improvement in clinical global impression, quality of life, quality of sleep, anxiety, and disability. Compared with placebo, quetiapine might cause more adverse effects of extrapyramidal side effects, sedation, somnolence, dizziness, fatigue, constipation, dry mouth, increased appetite, and weight gain.

The findings from this study underscore the efficacy of quetiapine as monotherapy for acute bipolar depression. It also highlighted the protective effect of quetiapine for the switching into mania. Limit data did not support the use of quetiapine in child and adolescents.