Changes in regional cerebral blood flow following light treatment for seasonal affective disorder: responders versus nonresponders.

BACKGROUND: Several brain imaging studies of antidepressant pharmacologic treatment utilizing single photon emission computed tomography (SPECT) have reported a normalization of deficits in cerebral blood flow (CBF) associated with recovery; other studies report no change, or a reduction in CBF following successful treatment. There have been no published SPECT studies of seasonal affective disorder (SAD) assessing response to light treatment in relation to changes in regional CBF (rCBF). In this study, we sought to test the hypothesis that increases in rCBF would be observed in SAD patients who responded to light treatment. METHODS: Ten depressed patients with SAD underwent functional brain imaging studies with 99mTc-hexamethylpropyleneamine oxime SPECT before and after light treatment. RESULTS: Relative increases in rCBF were observed in all brain regions compared to cerebellum in treatment responders, whereas nonresponders showed no change or decreases in rCBF relative to cerebellum. Significant differences in mean percentage change in rCBF between responders (n = 5) and nonresponders (n = 5) were detected in frontal and cingulate cortex, and thalamus. CONCLUSIONS: These findings provide preliminary support for the hypothesis that an increase in rCBF is associated with recovery from depression in SAD.