Enhanced inflammatory and T-helper-1 type responses but suppressed lymphocyte proliferation in patients with seasonal affective disorder and treated by light therapy

Abstract Background Animals show seasonal changes in the endocrine and immune system in response to winter stressors. Even though increased inflammation has been implicated in the pathophysiology of depression, whether immune disorder is a key mediator in seasonal affective depression (SAD) is unknown. Here, we hypothesized that short photoperiods in winter may induce inflammatory response, which contributes to SAD, and that light treatments should normalize immune function and improve depressive symptoms. Methods Twenty patients with a diagnosis of SAD, and a score on the HAM-29 of 20 or higher were recruited for this study. Twenty-one healthy subjects with no personal and family history o…