Electroretinography in seasonal affective disorder

Retinal mechanisms have been hypothesized in the pathophysiology of seasonal affective disorder (SAD). Electroretinography (ERG) is a noninvasive electrophysiologic test that provides an objective measure of photoreceptor and retinal function. We conducted dark-adapted ERG examinations with a bright white light stimulus in a group of depressed, drug-free patients with seasonal affective disorder (6 men, 18 women) diagnosed by DSM-III-R criteria, and a group of sex- and age-matched control subjects (6 men, 16 women) during the winter. A significant difference was found between SAD patients and controls, but female SAD patients had lower ERG b-wave amplitudes than female controls, while male SAD patients had higher amplitudes than the matched controls. The ERG b-wave implicit times (times from onset of stimulus to peak of b-wave) were significantly longer in the left eyes of the male control subjects. These data may indicate subtle retinal changes in patients with SAD, but the results must be considered preliminary because of the small number of subjects studied and the large intersubject variability in the ERG procedure.