Therapies · lesson 8 of 10
Bright light therapy: the well-proven one
10,000 lux in the morning — how it works, who it helps, and how to use a light box.
7 min read · reviewed October 2026
Not red light — a signal to your brain
A light box works through your eyes, not your skin. Bright light reaches specialised light-sensitive cells in the retina — most responsive to blue-ish light — that report straight to your brain's master clock, shifting circadian timing and influencing mood systems. A red panel can't do this job (those cells respond poorly to deep red), and a light box doesn't do what red-light therapy claims. Different tools, different evidence.
The best-studied dose for seasonal affective disorder: about 10,000 lux of white light at the eyes for roughly 30 minutes, soon after waking. For comparison, a bright indoor room is usually only a few hundred lux.
A dimmer box gives 2,500 lux at your eyes. Roughly how long would a session need to be to match the classic dose?
Somewhere between 0 and 180 min.
Reveal the answer →
~2 hours
Dose is intensity × time: the classic protocols were ~10,000 lux for 30 minutes or ~2,500 lux for about 2 hours. That's why a small lamp that only reaches 10,000 lux a few centimetres from your face is a poor buy — you won't sit that close for long.
How strong is the evidence?
For winter depression, bright light is one of the best-supported non-drug treatments there is, with effects comparable to antidepressant medication in controlled trials. It has also shown benefit in non-seasonal depression.
How it works →
Winter depression is often tied to a body clock that drifts later as mornings get darker. Morning light shifts the clock earlier and acts on mood-regulating pathways through the retina's direct connections to the brain. Timing matters: morning light moves your clock earlier; late-evening light pushes it later.
What the studies show →
A meta-analysis of randomized trials found bright light for seasonal depression — and for non-seasonal depression — had effect sizes similar to most antidepressant drug trials, while noting that only about 13% of the studies met its quality criteria (Golden et al., American Journal of Psychiatry, 2005). In a placebo-controlled trial in non-seasonal major depression, 10,000 lux for 30 minutes each morning beat placebo both alone and combined with fluoxetine, while fluoxetine alone did not beat placebo (Lam et al., JAMA Psychiatry, 2016).
Using a light box well
- Use it daily within about an hour of waking — ~30 minutes at 10,000 lux, or as your clinician advises.
- Sit at the distance where your box actually delivers 10,000 lux — check the manual.
- Keep your eyes open with the light in view, slightly above and in front of you. Don't stare into it; read or eat breakfast.
- If winter low mood returns every year, start as the days shorten and continue through the dark months.
- Avoid late-evening sessions unless advised — they can push your sleep later.
- Give it a couple of weeks. If you're not improving, or feel worse, see a clinician.
What to look for in a light box
10,000 lux at a stated, practical distance; white light with UV filtered out; and a surface big enough that small head movements don't take you out of the beam. Colour-changing 'mood' lamps and ordinary daylight bulbs don't qualify — looking bright isn't the same as 10,000 lux at your eyes.
You want to treat winter low mood. Which option matches the evidence?
- A 660 nm red-light panel on your chest
- A 10,000-lux white light box used in the morning
- A PEMF mat on an 'alpha wave' setting
- A warm, dim lamp in the evening
Show the answer →
B.A 10,000-lux white light box used in the morning
Bright white light at the eyes in the morning is the studied treatment. Red light acts (if at all) on the skin it reaches, not your body clock, and evening light pushes your rhythm the wrong way.
Free outdoor morning light, dim evenings and a fixed wake time — the Sleep track covers the daily light habits a box builds on.