SAD lamps: what's a real light box and how to use one

Seasonal affective disorder (SAD) is a recognised pattern of depression occurring at the same time each year, most commonly with onset in autumn or winter and remission in spring. Bright-light therapy is an evidence-based non-pharmacological option. The two studies cited on this page cover non-seasonal depression and SAD prevention rather than SAD treatment, so read them with that in mind.

What the evidence shows#

A 2019 Cochrane review (Nussbaumer-Streit et al.) looked at light therapy for preventing SAD, not treating it. The review found only one small, low-quality trial (46 people) comparing bright light, infrared light, and no treatment as a preventive measure, and drew no conclusions about efficacy because the evidence was too limited. It did not compare light therapy against antidepressants.

Lam et al. 2016 (JAMA Psychiatry) is a trial in adults with non-seasonal major depression, not SAD. Light therapy alone significantly outperformed placebo; fluoxetine alone did not reach statistical significance over placebo; the combination of light and fluoxetine had the largest effect. Effects typically appeared within a few weeks of consistent use.

What a "real" light box is#

The specifications matter. Many consumer products marketed as "SAD lamps" don't meet them:

• Intensity: 10,000 lux at the distance you'll actually use it (typically 16–24 inches from the face). Many low-cost lamps quote intensity at unrealistic distances.
• Spectrum: Broad-spectrum white light. UV is filtered out in compliant medical devices.
• Size: A larger panel makes consistent eye exposure easier without staring directly at the unit.
• Certification: Look for CE marking.

How to use it#

The standard protocol from the clinical trials:

• 30 minutes per session at 10,000 lux.
• Within the first hour of waking. Earlier is generally better.
• Eyes open: the light needs to reach the retina. You can read, eat breakfast, work. You don't need to stare at the box.
• Daily, throughout the dark months.

Shorter sessions at lower lux are sometimes recommended for sensitive users (e.g. 20 minutes at 5,000 lux), but the evidence base is strongest for 30 minutes at 10,000 lux.

Side effects#

Bright light therapy is well-tolerated. Reported side effects include:

• Eye strain or headache, particularly in the first week
• Nausea (rare)
• In bipolar disorder, light therapy can occasionally trigger hypomania; clinical supervision is advised.

People with retinal conditions (macular degeneration, retinal detachment) should consult an ophthalmologist before starting.

Where it fits in NHS care#

NICE guideline NG222 (depression in adults) says people with winter depression who want to try light therapy instead of antidepressants or psychological treatment should be told that the evidence for its efficacy is uncertain. Light boxes are not routinely provided on the NHS in all areas, but GPs can recommend specific products. In Scotland and parts of England, some occupational therapy services have light boxes available for trial.

If you suspect you have SAD, the appropriate first step is a GP appointment, not buying a light box independently. SAD overlaps with non-seasonal depression and other conditions in ways that affect treatment choice.

What this isn't#

Bright light therapy is for SAD and certain delayed sleep phase disorders. It is not a treatment for general low mood, fatigue, or non-seasonal depression. For those, NICE guidance points to other first-line interventions.

It also is not the same as the LED panels marketed as "red light therapy" (see the red light page). Different wavelengths, different evidence base, different indications.