The effect of bright light therapy on depressive symptoms in adults with intellectual disabilities: Results of a multicentre randomized controlled trial

BACKGROUND: Although a large number of adults with intellectual disabilities have depressive symptoms, non‐pharmacological treatments are scarce. The present authors investigated whether bright light therapy (BLT) is effective in decreasing depressive symptoms compared to care as usual. METHODS: This multicentre randomized controlled trial consisted of three study groups (10,000 lux BLT, dim light BLT and a no‐BLT group). Participants received BLT for 30 min in the morning (14 consecutive days), additional to their regular care. Primary outcome was as follows: depressive symptoms measured with the ADAMS Depressive Mood subscale 1 week after the end of BLT (same time period in the no‐BLT group). RESULTS: Forty‐one participants were included in our trial. In both BLT groups, a significant decrease in depressive symptoms was seen. No significant differences were found between 10,000 lux BLT and no‐BLT (p = .199) and no significant differences between dim light BLT and no‐BLT (p = .451). A minimum amount of side effects and no adverse events were reported. CONCLUSIONS: In both BLT interventions, a decrease in depressive symptoms was seen. With 10,000 lux BLT, depressive symptoms decreased even below the clinical cut‐off point, which makes BLT a promising intervention for clinical practice.