LongevityApril 27, 2026·4 min read
By the CIRRUS Editorial Team — how we write and source this
Light therapy for seasonal affective disorder: the specific protocol the evidence actually supports
Not all light boxes and usage patterns are equally effective — the trial evidence points to specific intensity, timing, and duration parameters.
Bright light therapy has some of the strongest evidence of any non-pharmacological treatment for seasonal affective disorder, with multiple randomized trials and meta-analyses finding effect sizes comparable to antidepressant medication for this specific condition — a notably strong evidence base for a non-drug intervention.
The trial-validated protocol is more specific than casually sitting near a bright lamp: typically 10,000 lux light intensity, used for 20-30 minutes each morning, ideally shortly after waking, with the light positioned at an angle to indirectly reach the eyes rather than requiring direct staring at the source — deviating meaningfully from these parameters (lower lux, evening timing, inconsistent use) has less supporting trial evidence and anecdotally less effect.
Timing appears to matter mechanistically, not just as a scheduling convenience — morning light exposure is thought to help realign circadian rhythm timing that's disrupted in seasonal affective disorder, which is part of why evening use hasn't shown comparable results in trials and in some cases has been associated with sleep disruption instead of benefit.
This article is general health information, not medical advice, and doesn’t replace evaluation by your own physician. Talk to a doctor about anything specific to your own diagnosis or treatment.