Light Therapy for Depression: What It Is and How to Use It
Light therapy is sometimes treated as a vague wellness suggestion — "get outside more" — when it's actually a specific, protocol-driven treatment with real evidence behind it, most established for seasonal affective disorder but genuinely useful in other contexts too. Getting the details right (brightness, timing, duration) is most of what determines whether it actually works.
Last updated September 2026
The actual protocol
A light box delivering 10,000 lux — about 20 times brighter than typical indoor lighting — used for about 30 to 45 minutes, first thing in the morning, is the standard evidence-based protocol. Morning timing isn't arbitrary: it's specifically what helps reset circadian rhythm, which is a large part of how this treatment works. The box is used at a specified distance with the light entering peripheral vision (not requiring you to stare directly into it), while doing something else — reading, eating breakfast, working.
A real light box filters out harmful UV wavelengths, unlike sitting near a bright window or under ordinary room lighting, which is why an actual light therapy device matters rather than just "more light exposure" generally.
How quickly it works, and for how long you'd use it
Effects typically build over one to two weeks rather than working immediately, and for seasonal depression it's generally used consistently across the darker months (fall through spring), not just during an acute flare. Stopping and expecting the effect to persist indefinitely isn't how it works — it's more like an ongoing daily treatment during the relevant season than a short course.
Beyond seasonal depression
The strongest evidence is for seasonal affective disorder, but light therapy also shows modest, real benefit for non-seasonal depression, and it's specifically used for postpartum depression — where the circadian disruption from irregular infant feeding schedules makes the mechanism especially relevant, alongside its role in resetting sleep patterns more broadly.
Who should check with a provider first
Light therapy can trigger a manic or hypomanic episode in someone with bipolar disorder, which is a real reason to confirm that diagnosis isn't in the picture before starting on your own — see the PMDD-versus-mood-disorders comparison if you're not sure. People with certain eye conditions, or taking medications that increase light sensitivity, should also check with a provider before starting rather than assuming it's automatically safe because it's non-medication.
Worth discussing with your provider
Educational information only — general patterns that vary by person. This is not medical advice, a diagnosis, or a substitute for care from your own clinician.
More from Education