Project 170885

Seasonal affective disorder (SAD) is a condition characterized by cyclic fall and winter depression followed by spring and summer remission. Although the origin of the disorder is not known, the consensus is that SAD patients are more susceptible to the seasonal decrease in light exposure and that light therapy is the treatment of choice for these patients. However, both the susceptibility to light changes and the relationship between light and mood regulation remain unclear. Members of our group showed that SAD patients' retina is less sensitive to light. Given that light is transmitted by the retina to the brain, we do not yet know whether retinal changes contribute to the disorder via an impact on brain response to light. Recently, it was shown that is it possible to measure brain response to light in humans using functional magnetic resonance imaging (fMRI). The main goal of this three-year research program is to assess brain and retinal sensitivity to light in SAD patients. In this study, 32 patients with SAD and 32 matched healthy participants will be evaluated in both winter and summer in order to assess seasonal variation in both retinal and brain sensitivity to light. This study will contribute to a better understanding of the underlying mechanisms of SAD, which could lead to better treatment of the disorder as light therapy is effective in about 60% of the patients, and open new research avenues on other psychiatric desorders.

using fMRI and electroretinogram to assess seasonal variation in brain and retinal sensitivity to light in SAD patients