Do light therapy boxes help mood, sleep, and energy?

A light box shines bright, cool-white light toward your eyes while you sit nearby reading or eating breakfast. Trials used 10,000 lux for about 30 minutes a day in the morning, for 8 weeks^1,3.

Winter depression (SAD). A meta-analysis of randomised trials found large benefits from bright light (effect size 0.84) and from dawn simulation (0.73)⁶. In the Can-SAD trial, light matched fluoxetine, with a response in 67% of each group, and light worked sooner at one week¹. For more, see Natural Management of Seasonal Affective Disorder.

Other depression. A meta-analysis of 20 trials (881 people) found a modest benefit (standardised mean difference -0.41), but high risk of bias and inconsistency make the evidence poor². In an 8-week trial of 122 adults, light alone beat placebo (effect size 0.80), light plus fluoxetine did best (response 75.9% versus 33.3% on placebo), and fluoxetine alone did not beat placebo³. As an add-on to an antidepressant, earlier trials found no benefit⁶.

Sleep timing. The American Academy of Sleep Medicine endorses timed light therapy for adults with advanced sleep-wake phase disorder, for children and teens with delayed sleep-wake phase disorder, and for older adults with dementia, at a second-tier level of confidence⁴. In a trial of 60 young people with delayed sleep, everyone improved over three weeks whether given green or red light, so light's specific role is unclear, and relapse was common⁷.

Energy. The best evidence is in cancer survivors with fatigue: bright white light cut fatigue 17% more than dim red light over four weeks⁵. We found no good trials in healthy people, so do not expect a coffee substitute.

Dawn simulators and prevention. In a 95-person trial, a dawn simulator beat both bright light and placebo, although bright light did not beat placebo there, unlike in other trials⁸. Starting light therapy in autumn to prevent winter depression has only very low-quality evidence⁹.

Safety. In 50 people with SAD, 10,000-lux light caused no eye changes after weeks of use or, in 17 of them, after 3 to 6 years¹⁰. The side-effect profile compares well with medicines, but clinicians watch for hypomania and jitteriness, especially in the first days¹¹.

Not the same as red light therapy. Red-light panels use red and near-infrared wavelengths for different claims; see How Red Light Therapy Works.

Meta-analysis of randomised trials. Golden and colleagues searched PubMed for randomised trials of light therapy for mood disorders, and only 13% of studies met their criteria. Bright light for SAD (8 studies) had an effect size of 0.84 (95% CI 0.60 to 1.08), dawn simulation for SAD (5 studies) 0.73 (0.37 to 1.08), and bright light for non-seasonal depression (3 studies) 0.53 (0.18 to 0.89). Bright light as an add-on to antidepressants for non-seasonal depression (5 studies) had an effect size of -0.01 (-0.36 to 0.34), meaning no benefit. The authors noted that many reports lacked rigorous designs and that defining a placebo light is difficult⁶.

Light versus fluoxetine. The Can-SAD trial randomised 96 patients with winter depression to 8 weeks of 10,000-lux light for 30 minutes each morning plus a placebo capsule, or to a 100-lux dim light plus fluoxetine 20 mg a day. Response rates were 67% in both groups and remission 50% versus 54%, with light ahead at one week only. Fluoxetine caused more agitation, sleep disturbance and palpitations. There was no double-placebo group¹.

Non-seasonal depression. In Lam and colleagues' 8-week trial, 122 adults were randomised to light (10,000 lux, 30 minutes in the early morning), fluoxetine, both, or placebo. Mean improvements on the MADRS depression scale were 13.4 (light), 8.8 (fluoxetine), 16.9 (both) and 6.5 (placebo). Light alone (effect size 0.80, 0.28 to 1.31) and the combination (1.11, 0.54 to 1.64) beat placebo; fluoxetine alone (0.24, -0.27 to 0.74) did not. Response was 50% with light, 29% with fluoxetine, 75.9% with both and 33.3% with placebo³. Perera and colleagues' meta-analysis of 20 trials in 881 people found a standardised mean difference of -0.41 (-0.64 to -0.18) with heterogeneity of 60%, and rated the evidence poor².

A conflicting result. Avery and colleagues randomised 95 people with SAD to bright light (10,000 lux for 30 minutes at 6:00), dawn simulation (a 1.5-hour signal peaking at 250 lux) or a dim red placebo for six weeks. Dawn simulation beat the placebo and the bright light for remission and response, while bright light did not differ significantly from placebo. That contrasts with most other trials. The authors also found that hours of sunshine in the previous week predicted remission and response⁸.

Prevention. The Cochrane review of light therapy to prevent SAD found only one eligible study, in 46 people, with high risk of bias. SAD developed in 43% (6 of 14) with bright light, 33% (5 of 15) with infrared light and 67% (6 of 9) with no treatment. The risk ratio for bright light was 0.64 (0.30 to 1.38), which is very low-quality evidence⁹.

Bipolar depression. In a 6-week trial, 46 adults with bipolar depression on stable medication were randomised to 7,000-lux white light at midday or 50-lux dim red light. Remission was 68.2% versus 22.2% (adjusted odds ratio 12.6), and no one switched mood¹². It is a small trial in closely monitored people.

Sleep timing. The 2015 American Academy of Sleep Medicine guideline gave second-tier endorsement to timed light for adults with advanced sleep-wake phase disorder, children and adolescents with delayed sleep-wake phase disorder, and older adults with dementia⁴. In Richardson and colleagues' trial of 60 people aged 13 to 24 with delayed sleep-wake phase disorder, three weeks of green or red light after waking, with sitting or movement, produced no difference between groups. All improved, with effects on sleep timing of d = 0.30 to 0.46 after treatment, but relapse was common and 38% asked for more treatment⁷.

Energy and fatigue. Johnson and colleagues randomised 81 cancer survivors with fatigue to a bright white light device (n = 42) or dim red light (n = 39) for 30 minutes on waking for 28 days. Fatigue fell 17% more with bright white light (between-group d = 0.30), and both groups improved on mood and quality of life⁵.

Safety. Gallin and colleagues examined the eyes of 50 people with SAD before and after 30 minutes of 10,000 lux daily for 2 to 8 weeks, and again in 17 of them after 3 to 6 years (60 to 1,250 hours of exposure). They found no ocular abnormalities, but still recommended monitoring for people with existing eye disease or on photosensitising drugs¹⁰. Terman and Terman's review describes a favourable side-effect profile, with emergent hypomania and autonomic activation the main watch points¹¹.

Bottom line (confidence 3). Bright light likely helps winter depression about as well as an antidepressant and appears to help some non-seasonal depression, though trial quality is poor. For sleep timing the guideline-level support is narrow, and the evidence for general energy is thin. Light therapy is low-risk for most people, but those with bipolar disorder or eye disease need supervision.