There was a comprehensive study done on the effects of light therapy on people with bipolar 1 disorder. Especially those of us who can't take antidepressants because we are so prone to severe mania. My psychiatrist read the study and thought it was worth a try for my depressive episodes. It's been moderately effective. It has occasionally flip me into hypomania so he monitors my use carefully. It's the only treatment for depression I can use though.