The short version
- •Light therapy uses daily exposure to a bright light box (typically 10,000 lux for ~30 minutes in the morning) to treat depression — especially seasonal affective disorder (SAD).
- •It is a first-line treatment for SAD, with efficacy comparable to antidepressants, and has growing evidence for non-seasonal depression as well.
- •It works by acting on the circadian system and brain pathways that regulate mood, helping reset a disrupted body clock and lift mood.
- •It is non-drug, generally well-tolerated (mild side effects like eyestrain or headache), and relatively fast-acting — many people respond within 1-2 weeks.
- •Proper use matters: the right intensity, timing (usually morning), and duration; and caution/medical guidance is needed in bipolar disorder (switch risk) and certain eye conditions.
- •For patients with a seasonal pattern, light therapy is a simple, evidence-based tool that can be used alongside other treatments including ketamine.
What it is
Light therapy (bright light therapy) is the therapeutic use of daily exposure to bright artificial light, most commonly delivered by a light box providing about 10,000 lux of broad-spectrum white light (with UV filtered out) for roughly 20-30 minutes, typically in the morning. Its best-established use is seasonal affective disorder — depression with a seasonal (usually fall/winter) pattern thought to involve circadian rhythm disruption and reduced light exposure in darker months. Light therapy is believed to work by acting on the circadian system (the body clock) and on serotonergic and other mood-regulating pathways, helping to re-entrain a shifted rhythm and lift mood. Beyond SAD, accumulating evidence supports light therapy for non-seasonal depression too, often as an adjunct. It is non-pharmacological, generally well-tolerated, and relatively rapid in onset. Correct parameters matter — intensity, wavelength, timing, and duration — and certain situations (bipolar disorder, retinal disease, photosensitizing medications) call for medical guidance.
What it helps with
First-line treatment, with efficacy comparable to antidepressants for the seasonal pattern.
Growing evidence supports it as an adjunct or treatment for non-seasonal depression.
Bipolar depression
Can help but requires caution and clinical guidance due to the risk of triggering a mood switch.
Properly timed light helps re-align a disrupted body clock that contributes to sleep problems.
What to expect
A light box, daily
~10,000 lux for 20-30 minutes, usually within an hour of waking, sitting near the box with eyes open (not staring at it).
Relatively fast
Many people notice improvement within one to two weeks.
Mild side effects
Occasional eyestrain, headache, or jitteriness, usually managed by adjusting timing or distance.
Get the parameters right
Intensity, timing, and duration matter; bipolar disorder and eye conditions warrant medical guidance.
The evidence
Light therapy is an evidence-based, first-line treatment for seasonal affective disorder. A landmark review and meta-analysis (Golden 2005) found bright light therapy efficacious for seasonal depression with effect sizes comparable to antidepressant medication, and supportive evidence for non-seasonal depression. It is recommended in clinical guidelines for SAD, and is increasingly used as an adjunct in non-seasonal depression.
How it pairs with ketamine
For patients whose depression has a seasonal component, light therapy is a simple, low-risk, evidence-based tool that complements other treatments. It addresses a specific circadian contributor that ketamine does not target directly, so the two can be used together — ketamine for a treatment-resistant depressive episode and light therapy to address the seasonal/circadian driver and support maintenance through darker months. As with any treatment in someone with bipolar disorder, the switch risk of light therapy is managed with clinical guidance, the same caution that applies to ketamine and antidepressants.
Frequently asked
Does light therapy actually work for depression?
Yes, particularly for seasonal affective disorder, where it's a first-line treatment with effectiveness comparable to antidepressants. There's also growing evidence for non-seasonal depression. It works by acting on the circadian system and mood pathways, and many people respond within one to two weeks.
How do I use a light box correctly?
Typically a 10,000-lux box for about 20-30 minutes in the morning, sitting near it with your eyes open but not staring directly at it. Intensity, timing, and duration all matter, so following guidance (and getting medical input if you have bipolar disorder or an eye condition) is important.
Is light therapy safe?
For most people, yes — side effects are usually mild (eyestrain, headache, occasional jitteriness). The main cautions are bipolar disorder (light can trigger a mood switch, so it's used with clinical guidance) and certain eye conditions or photosensitizing medications.
Can I use light therapy with ketamine?
Yes. They target different things — ketamine the depressive episode, light therapy the seasonal/circadian contributor — so they're compatible and can be used together, especially for depression with a seasonal pattern.
References
- Golden RN et al. 2005, American Journal of Psychiatry. Review and meta-analysis finding bright light therapy efficacious for seasonal (and supportively non-seasonal) depression, with effect sizes comparable to antidepressants. PMID 15800134