Effectiveness of bright light therapy in patients suffering from unipolar or bipolar depression; A naturalistic study

Background and objectives Depressive disorders, both unipolar (MDD) and bipolar (BD), impact patients and society greatly. In bipolar depression and seasonal affective disorder the episodic nature and periodicity relate to changes in circadian rhythms. Bright light therapy (BLT) is thought to ameliorate symptoms of depression through its influence on circadian rhythms. Effectiveness of BLT has not been thoroughly established in real-world clinical samples. Methods For seventy-four patients with depression Inventory of Depressive Symptoms – Self Rated (IDS-SR) scores were available through Routine Outcome Monitoring (ROM) used in BLT in the outpatient clinic for mood disorders. Patients received one or two weeks of add-on BLT as usual care. Patients suffering from MDD ( n = 33, 60.6 % female, mean age 36.1 ± 11.5 years) were compared to patients suffering from BD ( n = 41, 70.7 % female, mean age 45.0 ± 14.5 years) and changes in individual symptoms were analyzed for these two groups as well as the whole cohort. Results IDS-SR scores decreased significantly in both groups of patients and did not differ in effect size between the groups. Explorative analyses of the effects on individual items of the IDS-SR showed that items related to core symptoms of depression such a as mood, concentration and energy level showed the largest improvements. Conclusion Self-report depressive symptoms in patients suffering from either MDD or BD decreased in this naturalistic cohort after receiving BLT.