A reader asks:

 I used a light box for about 10 days, and ended up experiencing anxiety and irritability, even after cutting back on the time of exposure (from 20 to 10 minutes), and increasing the distance between my eyes and the light box by 6 and 12 inches. Does this mean I am just one of those people who cannot use a light box?

Answer:

You may be correct that your anxiety is a side effect of light exposure. But not necessarily. Do you get equally anxious when outdoors in sunlight? It seems that you should be working under clinical supervision, not self-treating. There are too many possible factors that might interact, and a Q&A forum such as this is not the place to do it. One possibility is that you are reacting specifically to the far-blue component of light from the box. If so, you could try screening it out with wrap-around blue-blocking lenses which maximize transmission of longer wavelengths (see 65% model at http://www.noir-medical.com/). If your anxiety persists, you should abstain from light therapy and seek an alternate treatment.