Bright light therapy works for about 40% of depression patients, analysis shows

Bright light therapy, which is sometimes used to treat seasonal affective disorders, also works for people with other types of depression, a new analysis has found.

An estimated 40 per cent of patients with depression responded to bright light therapy (BLT), which mimics sunlight, according to the research review published in JAMA Psychiatry.

That’s compared with 23 per cent among the control group, which included people who got lower levels of light exposure, antidepressants, or a placebo.

BLT has long been recommended for people with seasonal affective disorder (SAD), a type of depression that can sap people’s energy or affect their sleep schedule and typically hits during the darker winter months.

But the new findings indicate this light therapy could also be helpful for patients with non-seasonal depression. Given an estimated 50 per cent of depression patients don’t respond to initial treatments, the researchers said, they also suggest it could serve as a cheaper first-line therapy.

“BLT may be able to serve as [an additional] treatment in several locations around the globe and, consequently, in the more diverse economic environments,” the study authors from Brazilian universities said.

Their analysis included nearly 860 patients across 11 studies conducted between 2005 and 2024, and they used light boxes with an intensity of 5,000 to 10,000 lux of light, which is the level of exposure recommended by experts.

Across the studies, patients treated with BLT were more likely to respond to treatment and see their depression symptoms subside, and saw a greater reduction in depression scores compared with the control group.

BLT patients saw positive results regardless of how long researchers tracked them, the analysis also found. Even so, none of the studies followed patients for longer than a few weeks.

“Our analysis revealed that a treatment duration of one week may be as effective as a six-week duration,” Artur Menegaz de Almeida, the study’s lead author and a medical student at the Federal University of Mato Grosso (UFMT) in Brazil, told Euronews Health.

“However, this finding requires further investigation to better understand the time-response relationship in bright light therapy”.

It’s also not entirely clear why light appears to affect mood, Menegaz de Almeida added. Based on mice studies, researchers think that when light passes through the eyes, it could act as a stimulus for parts of the brain that regulate mood, affect, and the circadian rhythm, or the body’s internal clock.

“Since bright light therapy has been shown to benefit both seasonal affective disorder (SAD) and non-seasonal depressive disorders, it is possible that a similar mechanism is involved,” Menegaz de Almeida said.

He also emphasised that common artificial light may not be strong enough to regulate people’s moods, given “the light we assessed is not the same as a typical sun-lamp”.