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

The trial did not reach its planned sample size. 41 participants were included, but the aim was at least 57 participants in each group. With 12, 15 and 14 participants assigned, the study was small and may not have enough power to detect differences. One participant was excluded after the intervention for not following the 14-day schedule. Participants and caregivers were not blinded to the lightbox brightness. Many participants were taking psychotropic medication, especially antipsychotics, so bright light therapy was tested as an add-on to usual care, not as stand-alone treatment. Baseline sex distribution differed between groups and was corrected for in analyses. When participants with fewer than 10 bright light days were excluded, the primary outcome still showed no significant between-group differences. No participant had a major depressive disorder at baseline, so findings may not apply to severe depression.

PB, DF, HH and PH report grants from the Dioraphte Foundation and Foundation for Support VCVGZ for the conduct of the study. PB, DF, HH and PH report funding from three care provider centres of the HA-ID Consort (Abrona, Amarant and Ipse de Bruggen) during the study.

Do not conclude that bright light therapy is proven to reduce depressive symptoms in adults with intellectual disabilities. The primary comparison against usual care was not significant, the dim light group also showed within-group decreases, and the trial was small with many participants taking psychotropic medication.