Light therapy beats ionization for SAD

Light therapy is the better option for winter SAD, and there isn’t strong evidence that negative air ionization works well enough to recommend it as a replacement.

Here’s the deal: A few small studies in the 1990s and early 2000s suggested that high-density negative ions (think a few million per cubic centimeter) might lift mood in SAD. But the effect is modest at best. A 2006 study from Columbia that compared ions to light therapy found that light therapy worked significantly better, and that high-density ions were only marginally better than placebo.

You rarely see negative ionization mentioned in clinical guidelines for SAD anymore. Light therapy has consistently better evidence — it works for about 60–80% of people when used correctly, and it doesn’t require you to buy some device that may or may not put out the right ion density (most consumer ionizers don’t hit the levels used in studies anyway).

The “late winter” detail doesn’t change much. If you’re struggling in February or March, light therapy is still your best bet. Ionization isn’t harmful, but it’s not where I’d put my money.

Buy a proper 10,000 lux light box instead.