Review of: Youngstedt SD et al, Mil Med 2021 (Epub ahead of print)

Study type: Randomized, sham-controlled trial

As stated in the previous brief, PTSD is difficult to treat, and numerous interventions for PTSD have failed with veterans. This study took a different approach; it is the first randomized controlled trial of light therapy for PTSD.

Conducted at the VA Medical Center in Columbia, South Carolina, this study randomized 69 veterans with combat-related PTSD (from Afghanistan and/or Iraq) to 4 weeks of morning bright light treatment or a placebo. Those with a history of winter depression were excluded.

Light therapy consisted of 30 minutes of 10,000 lux ultraviolet-filtered white light within one hour of arising. The placebo was an inactivated negative ion generator, which has been used to control for light therapy in other studies. Participants were blindly rated on the Clinician-Administered PTSD Scale (CAPS) and Clinical Global Impressions scale (CGI). Self-reported measures of depression, anxiety, side effects, and sleep were elicited at baseline and upon completion of the study. Sleep variables were indirectly measured via continuous wrist actigraphic recording. Approximately two-thirds of the participants in the study were simultaneously receiving other treatments for PTSD. The study was funded by the VA.

Bright light significantly improved CAPS and CGI scores, with a large effect size (1.1) compared to placebo. Additionally, significantly more subjects receiving bright light achieved a response (reduction > 33%) compared to placebo (44.1% vs 8.6%). However, no participant achieved remission from PTSD. Remarkably, scores for depression, anxiety, and sleep did not differ between treatment and control. There were no significant side effects with light therapy, though headache and eye strain can occur and it should be used with caution in ocular disease. Although the subjects were not blinded to their treatment, there was no significant difference in expectation of improvement between treatment and control.

Most mental illnesses, including PTSD, are associated with circadian rhythm abnormalities, which may explain some of these benefits. Light therapy also modulates serotonin. However, this doesn’t explain why sleep and depression did not improve with light therapy.

We reached out to the lead author (Youngstedt), who shared his impression that light therapy improved symptoms unique to PTSD.

TCPR’s Take
This well-designed study found bright light therapy made a meaningful difference in veterans with combat-related PTSD. Although it’s only one study, we don’t have many options for this population, and light therapy has a good safety record in depression. Consider it in patients who want a non-medication approach, and in those with seasonal depression (see TCPR Feb 2019 for directions on light therapy).