Morning sunlight reduces length of hospitalization in bipolar depression

Background: Bright artificial light improves non-seasonal depression. Preliminary observations suggest that sunlight could share this effect. Methods: Length of hospitalization was recorded for a sample of 415 unipolar and 187 bipolar depressed inpatients, assigned to rooms with eastern (E) or western (W) windows. Results: Bipolar inpatients in E rooms (exposed to direct sunlight in the morning) had a mean 3.67-day shorter hospital stay than patients in W rooms. No effect was found in unipolar inpatients. Conclusions: Natural sunlight can be an underestimated and uncontrolled light therapy for bipolar depression. Limitations: This is a naturalistic retrospective observation, which needs to be confirmed by prospective studies.