Light therapy in bipolar SAD: screen first, start low

The risk of hypomanic switch with light therapy in bipolar-spectrum SAD is real, especially in late winter when circadian timing is sensitive, so screen with the Mood Disorder Questionnaire (MDQ) or Hypomania Checklist (HCL-32) first, and if positive, start with very brief morning exposure (15–20 min at 2,000–5,000 lux) and monitor closely.

Late winter is tricky because the days are getting longer already—adding light therapy can push someone who’s already on the edge of springtime activation into hypomania. The standard 30–60 minutes at 10,000 lux is too aggressive for bipolar spectrum. I think the evidence supports starting at half that dose and checking in after three to five days.

The screening piece is non-negotiable in my book. You want the MDQ or HCL-32 because they catch subtle bipolar II or cyclothymic features that a simple “have you ever been manic?” question won’t. If someone screens positive, you don’t necessarily say no to light therapy, but you change the risk/benefit calculus—you might want a mood stabilizer onboard, you use lower intensity, and you have a clear “stop if you feel wired” plan.

The specific timing risk in