The effect of bright light therapy on irritability in bipolar depression: a single-blind randomised control trial

Objective: The symptom-complex irritability, widely used in descriptions of bipolar patients’ manic and mixed states, also represents a common feature in depressive phases. Irritability negatively affects the clinical course of depression, leading to a higher risk of treatment non-adherence, violence, and suicide attempts. Nevertheless, proportional attention from the scientific literature seems to be scarce. We conducted the first randomised controlled trial with the aim of evaluating BLT as a possible therapeutic strategy for irritability in bipolar depression. Methods: 180 inpatients were randomly assigned to: Group A exposed to bright light therapy (BLT) daily, or Group B treated with pharmacotherapy only. A qualitative assessment of irritability was performed after a 4-week program. Results: Group A showed about one-third fewer cases of irritability compared to Group B, this reduction was not related to the overall remission of depressive symptoms. Conclusions: The present study supports the usefulness of BLT in irritability in bipolar depression.