Bipolar type II depression is a very frequent condition for which we still have a significant lack of acute treatments. There is now consistent evidence that light-therapy treatment produced a significant decrease of depressive symptoms for seasonal and non-seasonal unipolar depression. But there are no long-term studies of light therapy for the treatment of non-seasonal unipolar depression. It is also important to note that many of these studies involved co-therapy with antidepressant drugs or sleep-deprivation, making the interpretation of the results even more difficult.