Grant: Operating Grant

Rates of seasonal affective disorder (SAD) range from 1 to 6 percent (highest at Northern latitudes). 40 percent of people with SAD switch to clinical depression and 25 percent of healthy people have seasonal changes in mood, energy, appetite and sleep affecting function. In 2008, we discovered that the mood supporting chemical serotonin is removed more in people brain scanned during winter than people brain scanned during the summer. This was published in the top psychiatry journal (Archives of General Psychiatry). This earlier study scanned different people in summer and winter. In the proposed study, we would like to brain scan the same people in summer and winter. Also, we would like to see if seasonal changes in serotonin removal are greater in people with SAD. Finally we would like to understand whether light exposure will decrease the serotonin removal.If the season change in serotonin removal is greater in SAD, then we should develop ways to prevent it. If light prevents the serotonin removal, we can then test out different ways of doing light exposure (timing, color etc.) so as to best prevent the serotonin removal in small groups of people, using the brain scan as a calibration. This would hasten development of better light treatment for preventing seasonal sadness in winter.