Light therapy for seasonal affective disorder in a clinical office setting

To determine predictors of response to light therapy (LT) for seasonal affective disorder, winter version, in a clinical office setting for patients with a spectrum of seasonality defined by the Seasonal Pattern Assessment Questionnaire (SPAQ).

A retrospective review was done of charts of 51 patients who had been treated with a 1-week light therapy intervention. Patient self-rated scales applied in a standard manner were used to measure clinical progress. The Beck Depression Inventory (BDI) with added atypical features was used as the primary outcome variable. Sleep patterns were analyzed and the effect of psychotropic medications on outcome was determined. Seven point scales were used to assess expected response and global response. The importance of having LT set up and available in an office setting was evaluated. Retrospective degree of disability was measured based on the SPAQ degree of problem. The severity of the depressive episode was determined based on BDI score at entry.

Seasonality (how a patient's symptoms vary as a function of the season of the year), degree of disability based on the SPAQ, and severity of depressive episode at entry based on the BDI predicted response to LT. Greater severity at baseline based on BDI score predicted less chance of attaining full remission within 7 days of treatment compared with patients with lower severity scores at entry on the BDI. Sleep patterns relative to a fixed treatment time of 7 AM did not predict LT response. Light therapy was effective on its own, and the results were mixed as to whether adding LT to an existing antidepressant medication produced superior results.

Degree of seasonality can be used as a predictor of response to LT and may be clinically useful when suggesting that patients consider a trial of LT.