A reader asks:

 I notice an antidepressant effect if I use my light box in the early morning. However, I am phase-advanced, so I do not sleep well if I use the light in the morning. However, when I use the light in the evening, I do not notice an antidepressant effect. Would I get the effect by using the light in the mid-morning plus the evening?


There is no harm trying, but we cannot confidently predict the result. It has been hypothesized that “early types” need a phase delay (from evening light) to show the antidepressant effect, while “late types” will respond to phase advances (from morning light). Thus far, there are no strong data to support for that hypothesis — most people respond to phase advances, regardless of their chronotype.

You might find the following trick helpful: use the light in late evening, right before bedtime, for one week. (You may find your sleep episode delays.) Then, immediately switch to morning light at your new wake-up time. That will give you the desired phase advance, and your sleep may stabilize without premature awakening.