Efficacy of light therapy for a college student sample with non-seasonal subthreshold depression: An RCT study

Abstract

Background: Light therapy has been successfully used to treat seasonal and non-seasonal depression, but there is limited evidence for its efficacy in subthreshold depression. This study examines the efficacy of light therapy for symptoms of depression and anxiety in non-seasonal subthreshold depression.

Methods: College students with non-seasonal subthreshold depression were recruited. The participants were randomly allocated to one of the three conditions: high- (LT-5000 lux) and low-intensity (LT-500 lux) light therapy conditions and a waiting-list control condition (WLC). The primary outcome was Hamilton Depression Rating Scale (HAMD), and secondary outcomes were Beck Depression Inventory-II (BDI-II) and state anxiety inventory (SAI), which were assessed at baseline (Week 0), during the trial (Week 4), and after completion of the light therapy (Week 8).

Results: A total of 142 participants completed the trial. The LT-5000 (effect size [d] = 1.56, 95% CI: 1.15 to 1.98) and LT-500 conditions (d = 0.84, 95% CI: 0.43 to 1.26) were significantly superior to the WLC condition. For the LT-5000, LT-500, and WLC conditions by the end of the 8-week trial, a response on the HAMD was achieved by 70.0%, 42.0% and 19.0% of the participants, and remission was achieved by 76.0%, 54.0%, and 19.0%, respectively.

Limitations: The subjects were not followed up regularly after completion of the trial.

Conclusion: Light therapy, both at high- and low-intensity, was efficacious in the treatment of college students with non-seasonal subthreshold depression. High-intensity light therapy was superior to low-intensity light therapy by the end of an 8-week trial.

Keywords: College student; Intensity; Light therapy; RCT; Subthreshold depression.