A reader asks:

I am new (last 10 or so days) to light box use and am still learning the ropes of all the different variables. I also seem to be prone to the anxiety side effect when I get too much light. On any given day, is there any way to tell when I have gotten “enough” light? I have tried stopping “early” but have not gotten enough of the antidepressant effect. I would like to be able to stop just short of the anxiety starting.


First off, 10 days is too soon to know confidently how much light you will need to establish and maintain the antidepressant effect. Clearly, you should extinguish the lights at first inkling of an anxiety side effect, and set your session shorter on the following days. You may be able to sustain a longer session by sitting farther from the light box — try this in steps of 6 inches. If you can tolerate a short session (say, 10 minutes) in early morning, you can try adding a second short session at midday. If the anxiety persists after a few weeks of such testing, it is just possible that you will need to investigate an alternate treatment approach, such as negative air ionization or medication.