Grant: Master's Award: Canada Graduate Scholarships

Seasonal affective disorder (SAD) is a type of clinical depression in which sufferers experience sad mood, low energy, sleepiness and weight gain in the winter with full recovery in the spring. In Canada, rates of SAD range from 1 to 6% (higher at northern latitudes). Unfortunately, there is virtually no information on the biology of SAD. Given the high rate of SAD in Canada and its impact on the health of Canadians, there is an urgent need for research to understand the biology of this illness to develop methods of prevention and treatment. Serotonin is a brain chemical that helps maintain healthy mood and having too little serotonin is associated with depressive symptoms like sad mood. In the brain, serotonin is removed by vacuum cleaner proteins called serotonin transporters (5-HTT). In 2008, we discovered that healthy people have more serotonin vacuum cleaners in winter than summer in brain areas that regulate mood. We think that the winter increase in 5-HTT levels leads to lower brain serotonin and winter depression. We also believe that this increase is caused by changes in light levels in the environment. In the 2008 study we brain-scanned different healthy people in the summer and winter. In this study, we would like to scan the same people (healthy and SAD) in both summer and winter. Most importantly, as we think that overly elevated 5-HTT levels lead serotonin loss and winter depression, we wish to see if seasonal changes in these protein levels are greater in people with SAD. We would also like to scan people with SAD before and after light therapy to determine if light exposure can normalize 5-HTT levels. If the seasonal change in 5-HTT levels is greater in SAD, we can develop ways to prevent the winter 5-HTT increase to treat or prevent SAD. If light exposure normalizes the winter increase in 5-HTT levels, we can use the brain scanner to determine what aspects (colour, intensity, etc.) best reduce the winter elevation to optimize SAD treatment.