Bright Light Therapy: Side Effects and Benefits Across the Symptom Spectrum

Background: Bright light therapy has been established for treatment of winter depression, or seasonal affective disorder (SAD). Analysis of side effects most often have focused on a narrow set of suspected symptoms, based on clinical observation (e.g., headache, eyestrain, nausea, insomnia, and hyperactivity). This study broadens the purview to a set of 88 physical and subjective symptoms that might emerge, remit, or remain unchanged relative to baseline, thus reducing bias toward assessment of presumed side effects.

Method: Eighty-three patients with SAD (DSM-III-R criteria for mood disorders with seasonal pattern [winter type] and National Institute of Mental Health criteria for SAD) received bright light therapy at 10,000 lux for 30 minutes daily in the morning or evening for 10 to 14 days. They completed a questionnaire (Systematic Assessment for Treatment Emergent Effects), rating symptom severity before and after treatment. Results were compared for morning or evening treatment and for responders and nonresponders.

Results: Several side effects emerged—mostly mildly—including jumpiness/jitteriness (8.8%), headache (8.4%), and nausea (15.9%), mirroring findings of past studies with a less inclusive scope. In most cases, remission rate equalled or exceeded emergence rate. Several nondepressive symptoms also showed large improvement, including poor vision and skin rash/itch/irritation. Being overactive/excited/elated showed greater emergence under morning light and greater remission under evening light. Emergence of nausea was greater than remission in responders.

Conclusion: The dominant effect of light treatment was improvement in bothersome symptoms. Although patients should be advised of side effects and guided in dose manipulations to reduce them, attention also should be drawn to the substantial benefit-to-risk ratio. Improvement of symptoms outside the depressive cluster, seen in both responders and nonresponders, may point to new therapeutic uses of light therapy.