Light & photobiomodulation
Bright Light Therapy for Depression
Graded on: depression scores, response and remission in winter seasonal depression and non-seasonal major depression on clinician-rated scales (SIGH-SAD, HAM-D, MADRS).
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How this letter has changedLatest: October 2026 · Added.
New device record. Randomized trials against dim light or an inactive device replicate a benefit on clinician-rated depression scales in winter seasonal depression and in non-seasonal major depression (Lam et al., JAMA Psychiatry 2016; PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 26580307. Menegaz de Almeida et al., JAMA Psychiatry 2025; PMID 39356500). Held at B rather than A because blinding is hard with a visible light and is not confirmed trial by trial, and one placebo-controlled trial found a benefit only on strict remission criteria (Eastman et al., Arch Gen Psychiatry 1998; PMID 9783558). The record carries the hypomania caution for bipolar disorder (Tuunainen et al., Cochrane 2004; PMID 15106233) and does not cover prevention, timing, colored light or sunlight after waking. Decided by Arnold Sandlow, D.C.PMID 26580307 PMID 39356500 PMID 9783558 PMID 15106233
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Bright light therapy means sitting near a special lamp, many times brighter than room light, for about 30 minutes a day. In studies of people with winter depression, and of people with depression at other times of year, it lifted mood more than a dim light did. It works best in the morning in some studies, though not in all. It is not the same as getting sunlight after waking, which has never been tested this way. In people with bipolar disorder, bright light can bring on an overexcited, high mood.
A letter describes the human evidence, not the product, the manufacturer, or the intervention's worth.
See the full evidence record →Graded on Depression scores, response and remission in winter seasonal depression and non-seasonal major depression on clinician-rated scales (SIGH-SAD, HAM-D, MADRS).
Why this gradeThe reasoning, and what the grade does not cover.
Grade B. Randomized trials replicate the effect on clinician-rated depression scales in two populations, winter seasonal depression and non-seasonal major depression, run by independent, government-funded groups in the United States and Canada, and pooled analyses from 2004 to 2026 point the same way (Golden et al., 2005; PMID 15800134. Menegaz de Almeida et al., 2025; PMID 39356500). Under the rule as revised in September 2026 a validated scale scored by a clinician blinded to treatment can carry an A. The letter is held at B because that blinding is not confirmed trial by trial: a participant can see whether a light is bright, so the placebos are dim lights or inactive negative ion generators, and how well the blind held is not reported across the trials. The placebo-controlled results are also mixed on their main analyses: Eastman et al. (1998; PMID 9783558) found no difference in mean scores at 4 weeks and a benefit only on strict remission criteria, and the 2004 Cochrane review found the overall effect short of statistical significance, with benefit in its high-quality and morning-light trials (PMID 15106233). Where a letter is disputed, EBL takes the lower one. Decided by Arnold Sandlow, D.C., in October 2026.
WHAT THIS GRADE DOES NOT COVERpreventing winter depression before it starts (one small trial, no conclusion; PMID 30883670); bipolar depression (positive but nonconclusive; PMID 31826657); morning rather than evening timing, where the main analyses differ (PMID 9783557, PMID 9783559); dawn simulators, blue-only, green or red light; any outcome beyond symptom scales, since no trial measures suicide attempts, hospitalization or relapse; and sunlight within 30 minutes of waking in healthy people, which no randomized trial has tested. It covers adults with winter seasonal depression or non-seasonal major depression treated with white light at about 10,000 lux (6,000 lux for longer sessions in one trial) for 30 to 90 minutes a day.
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Light therapy can trigger hypomania or mania in people with bipolar disorder. A Cochrane review of non-seasonal depression found hypomania more common on bright light than on the control treatment (risk ratio 4.91, about one case for every 8 people treated). A 2020 meta-analysis A study that pools the numbers from several trials into one combined estimate. of 7 trials in bipolar depression, where light was added to existing treatment, found no difference in mood switches. People with a bipolar history are screened by the treating clinician before a course of light, the same as before an antidepressant.
The evidence, in full14 papers, each linked to its PubMed record.
Winter seasonal depression. Terman et al. (Arch Gen Psychiatry, 1998; PMID 9783557): 158 patients, 10,000 lux for 30 minutes; morning and evening light did not differ on the main analysis and both beat a low-density negative ion placebo An inactive substitute made to look like the real treatment, so participants cannot tell which one they received.; morning light did better only on a stringent remission criterion; high-density negative ions also worked; NIMH-funded. Eastman et al. (Arch Gen Psychiatry, 1998; PMID 9783558): 96 patients, about 6,000 lux for 90 minutes a day for 4 weeks against a sham A fake version of a procedure or device used as the comparison, so participants cannot tell which one they received. negative ion generator; no difference in mean depression scores at 4 weeks, but more full or near-full remissions on morning light from week 3 (61% morning, 50% evening, 32% placebo by one criterion); NIMH-funded. Lewy et al. (Arch Gen Psychiatry, 1998; PMID 9783559): 51 patients, morning light shifted the body clock earlier and was more antidepressant than evening light; no placebo arm; NIH-funded. Lam et al. (Am J Psychiatry, 2006; PMID 16648320): 96 patients, 10,000 lux light plus placebo capsule against dim light plus fluoxetine 20 mg for 8 weeks; no difference between them, response 67% in each group; no double-placebo arm. Golden et al. (Am J Psychiatry, 2005; PMID 15800134): meta-analysis, bright light effect size How large a difference the treatment made, as distinct from whether the difference could be detected at all. 0.84 (8 trials) and dawn simulation 0.73 (5 trials) in seasonal depression. Chen et al. (J Affect Disord, 2024; PMID 38220102): network meta-analysis of 21 trials and 1,037 people; light beat control treatments, with the quality of evidence rated low. Wan et al. (Medicine, 2025; PMID 40629637): network meta-analysis of 17 trials and 773 patients; white light ranked above green, blue and red. Non-seasonal major depression. Lam et al. (JAMA Psychiatry, 2016; PMID 26580307): 122 adults, double-blind Neither the participants nor the people assessing them know who received the real treatment until the trial ends., 8 weeks, 10,000 lux for 30 minutes early in the morning; on the MADRS, light alone beat an inactive negative ion generator plus placebo pill (effect size 0.80) and light plus fluoxetine did best (1.11), while fluoxetine alone did not separate from placebo (0.24); funded by the Canadian Institutes of Health Research. Menegaz de Almeida et al. (JAMA Psychiatry, 2025; PMID 39356500): 11 trials and 858 patients, light added to treatment; remission 40.7% versus 23.5% (odds ratio 2.42) and response 60.4% versus 38.6% (odds ratio 2.34). Tong et al. (Asian J Psychiatr, 2024; PMID 39067131): 15 trials and 883 patients; standardized mean difference 0.48. Wang et al. (Gen Hosp Psychiatry, 2026; PMID 42097096): trials from 2020 to 2025; standardized mean difference 0.35 in non-seasonal major depression. Tuunainen et al. (Cochrane, 2004; PMID 15106233): 20 trials, mostly light added to drugs or sleep deprivation and mostly under 8 days; the overall benefit did not reach statistical significance, while high-quality trials (standardized mean difference 0.90) and morning-light trials did; hypomania was more common on bright light (risk ratio 4.91, number needed to harm 8). Kept in the record: Lam et al. (Can J Psychiatry, 2020; PMID 31826657), 7 trials and 259 patients with bipolar depression, light added to treatment improved Hamilton scores (standardized mean difference 0.43) with no difference in mood switches, evidence the authors call nonconclusive; Nussbaumer-Streit et al. (Cochrane, 2019; PMID 30883670), light to prevent winter depression, one eligible trial of 46 people, very low quality, no conclusion possible.
A clinician-rated depression scale (the SIGH-SAD for seasonal depression, the HAM-D or MADRS otherwise) at baseline and weekly through the first 8 weeks, because the trials measured change over 1 to 8 weeks and one found the benefit over placebo took 3 weeks to appear. In anyone with a history of bipolar disorder, signs of mood elevation as well as depression.
Evidence notes: randomized trial, meta-analysis
Endpoint The outcome a trial measures to decide whether the treatment worked, such as heart attacks, blood pressure or a symptom score. graded: Depression scores, response and remission in winter seasonal depression and non-seasonal major depression on clinician-rated scales (SIGH-SAD, HAM-D, MADRS) (clinician_rated)
Last reviewed: October 2026
Educational use only · Not medical advice · EBL grades published human evidence and does not recommend treatment. Stopping a prescription is a decision for your physician.
As studiedDose, form, population and duration for every use.
Light boxes, lamps and glasses sold for mood vary in brightness, spectrum and the distance at which the stated lux is reached. This grade describes white light at about 10,000 lux at the distance the trials used; blue-only, green and red light ranked below white light in a 2025 network meta-analysis (PMID 40629637).
A grade describes the intervention that was tested. Where the product on the shelf differs from it, this says so.
Primary evidence14 papers, each linked to its PubMed record.
Winter seasonal depression. Terman et al. (Arch Gen Psychiatry, 1998; PMID 9783557): 158 patients, 10,000 lux for 30 minutes; morning and evening light did not differ on the main analysis and both beat a low-density negative ion placebo; morning light did better only on a stringent remission criterion; high-density negative ions also worked; NIMH-funded. Eastman et al. (Arch Gen Psychiatry, 1998; PMID 9783558): 96 patients, about 6,000 lux for 90 minutes a day for 4 weeks against a sham negative ion generator; no difference in mean depression scores at 4 weeks, but more full or near-full remissions on morning light from week 3 (61% morning, 50% evening, 32% placebo by one criterion); NIMH-funded. Lewy et al. (Arch Gen Psychiatry, 1998; PMID 9783559): 51 patients, morning light shifted the body clock earlier and was more antidepressant than evening light; no placebo arm; NIH-funded. Lam et al. (Am J Psychiatry, 2006; PMID 16648320): 96 patients, 10,000 lux light plus placebo capsule against dim light plus fluoxetine 20 mg for 8 weeks; no difference between them, response 67% in each group; no double-placebo arm. Golden et al. (Am J Psychiatry, 2005; PMID 15800134): meta-analysis, bright light effect size 0.84 (8 trials) and dawn simulation 0.73 (5 trials) in seasonal depression. Chen et al. (J Affect Disord, 2024; PMID 38220102): network meta-analysis of 21 trials and 1,037 people; light beat control treatments, with the quality of evidence rated low. Wan et al. (Medicine, 2025; PMID 40629637): network meta-analysis of 17 trials and 773 patients; white light ranked above green, blue and red. Non-seasonal major depression. Lam et al. (JAMA Psychiatry, 2016; PMID 26580307): 122 adults, double-blind, 8 weeks, 10,000 lux for 30 minutes early in the morning; on the MADRS, light alone beat an inactive negative ion generator plus placebo pill (effect size 0.80) and light plus fluoxetine did best (1.11), while fluoxetine alone did not separate from placebo (0.24); funded by the Canadian Institutes of Health Research. Menegaz de Almeida et al. (JAMA Psychiatry, 2025; PMID 39356500): 11 trials and 858 patients, light added to treatment; remission 40.7% versus 23.5% (odds ratio 2.42) and response 60.4% versus 38.6% (odds ratio 2.34). Tong et al. (Asian J Psychiatr, 2024; PMID 39067131): 15 trials and 883 patients; standardized mean difference 0.48. Wang et al. (Gen Hosp Psychiatry, 2026; PMID 42097096): trials from 2020 to 2025; standardized mean difference 0.35 in non-seasonal major depression. Tuunainen et al. (Cochrane, 2004; PMID 15106233): 20 trials, mostly light added to drugs or sleep deprivation and mostly under 8 days; the overall benefit did not reach statistical significance, while high-quality trials (standardized mean difference 0.90) and morning-light trials did; hypomania was more common on bright light (risk ratio 4.91, number needed to harm 8). Kept in the record: Lam et al. (Can J Psychiatry, 2020; PMID 31826657), 7 trials and 259 patients with bipolar depression, light added to treatment improved Hamilton scores (standardized mean difference 0.43) with no difference in mood switches, evidence the authors call nonconclusive; Nussbaumer-Streit et al. (Cochrane, 2019; PMID 30883670), light to prevent winter depression, one eligible trial of 46 people, very low quality, no conclusion possible.
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("light therapy"[tiab] OR "bright light"[tiab] OR phototherapy[tiab]) AND (depression[tiab] OR depressive[tiab] OR "seasonal affective"[tiab]) AND meta-analysis[pt] AND 2024:2026[dp]Grades move when new trials publish. A free monthly email lists every grade EBL moved, with the reason and the trial behind it: the sign-up is on the Evidence Log →