Bright-Light Therapy: Evidence and Safety

What it is

Bright-light therapy means sitting in front of a specialized bright light box or lamp, sometimes called a SAD lamp, to simulate daylight, usually for a mood condition. [1] It is a clinical idea that has also become a consumer product. This page covers the evidence and the safety questions. It does not give lamp settings, distances or schedules; those depend on the person and the condition and belong with a clinician. Evidence labels used: established, promising but limited, mixed, insufficient evidence and Proper evidence not found (we looked and found nothing usable).

What it claims

Claims range from treating winter depression to improving energy, sleep timing or focus in healthy people. Only the first has meaningful trial evidence, and even that evidence has limits.

Seasonal affective disorder (SAD)

The NHS lists light therapy alongside antidepressants and talking therapies as a SAD treatment, but says it is not usually available on the NHS because there is not enough evidence to tell whether it works. [1] For prevention in people with a past history of SAD, a Cochrane review found only one eligible study, with 46 people and high risk of bias, and rated the evidence very low quality. [2] Label: mixed to insufficient evidence, depending on the question (treating a current episode versus preventing a future one).

Non-seasonal depression

• A 2024 meta-analysis of 15 randomized trials (883 patients) with major depressive disorder reported lower depression scores with bright light. [3]
• A 2025 meta-analysis in JAMA Psychiatry pooled 11 trials (858 patients) of bright light added to usual treatment and reported higher remission (40.7% versus 23.5%) and response rates. [4]
• An older Cochrane review (2004) described the quality of reporting as poor, and many studies did not report adverse effects systematically. [5]

Label: promising but limited as an add-on. These trials were small, and who counts as a "control" (dim red light, no light) varies. A mood-score change in a trial is not the same as a guarantee for you.

Side effects and cautions

• The 2004 Cochrane review found hypomania (an elevated, overactive mood state) was more common in the bright-light group than in controls. [5] People with bipolar disorder need specialist guidance first.
• The NHS advises speaking to a GP before trying light therapy, because it may be unsuitable with certain eye conditions or with medicines that increase light sensitivity. [1]
• The NHS also says a bought light box should be UV-free and carry a UKCA or CE mark, and its instructions followed. [1] Marks differ by country; this is UK advice. Other countries' rules were not verified for this page.
• Eye and skin safety for light devices more broadly: Light Devices: Eye and Skin Safety.

Who should check first

People with eye disease or past eye surgery, bipolar disorder, a history of mania, or light-sensitizing medicines, and anyone with severe depression or thoughts of self-harm. In the US, the 988 Suicide & Crisis Lifeline can be reached by calling or texting 988. A lamp is not a substitute for care; see talking with a health professional.

Wellness use in healthy people

Proper evidence not found in the sources we checked that bright-light lamps improve mood, focus or sleep in people without a diagnosed condition. Timing and body-clock questions are covered in morning light and the circadian rhythm and circadian rhythm disorders.

How to evaluate a product claim

1. Does it name the condition and cite trials in that condition?
2. Does it use "lux" at an unstated distance? A brightness number is meaningless without distance and duration; see light device specifications.
3. Does it promise results without telling you who should not use it?