A reader asks:

Can light therapy be useful for depression that is not related to seasonal change, i.e., major depressive episodes, cycling/chronic depression?

Answer:

Although these applications have not been studied as extensively as light therapy for SAD, all indications are Yes. Clinical trials have been completed showing benefit of light therapy to non-seasonal recurrent, chronic, bipolar and even rapid cycling depression. We are not yet sure whether the same “early morning light prescription” as is used for SAD will prove optimal for non-seasonal depression. However, the most recent trials show clear benefit of morning light compared to placebo. In cases of bipolar and rapid cycling depression — variants of “manic depression” — light therapy should not be attempted without using a mood stabilizing drug, because of the risk of a sudden switch to the disruptive “high” state. This clearly implies that the treatment must be done under professional guidance and supervision.