Light therapy is one of the few non-pharmacological treatments with solid evidence for seasonal depression and sleep disorders. Here is how it works and how to use it correctly.
Autumn. Dark by four in the afternoon. You come home in the dark. Wake up in the dark. Mood drops. You crave carbohydrates and sleep. "Just the autumn blues," you tell yourself. Maybe. But those blues have a biological mechanism — and an equally biological solution.
Light therapy (phototherapy) involves exposure to bright artificial light at an intensity of 2,500 to 10,000 lux for 20 to 60 minutes, typically in the morning. A standard incandescent or fluorescent lamp produces 200 to 500 lux — fundamentally different. A sunny day outdoors delivers 10,000 to 100,000 lux.
Light acts on melanopsin-containing retinal cells that transmit time-of-day signals to the suprachiasmatic nucleus — the brain's circadian pacemaker. This resets the circadian clock and suppresses melatonin production during daytime hours.
Seasonal affective disorder (SAD) — the primary indication, supported by extensive research. Light therapy is a first-line treatment for SAD, equivalent to antidepressants, with considerably fewer side effects.
Non-seasonal depression: meta-analyses show that light therapy is also effective for depression not tied to season — particularly when added to antidepressant medication. Circadian rhythm disruptions: delayed sleep phase disorder (morning light shifts the clock earlier), shift work sleep disorder, jet lag recovery.
Timing: morning, within the first 30 to 60 minutes after waking. This is when light has the strongest phase-advancing effect on the circadian clock. Evening light has the opposite effect — it shifts the rhythm later.
Intensity: at least 10,000 lux (for a 10,000-lux lamp — 20 to 30 minutes; for 2,500 lux — about an hour). Distance from the lamp: typically 30 to 60 cm.
Position: do not look directly into the lamp — look past it or engage in another activity (breakfast, reading). Eyes must be open — light needs to reach the retina.
Consistency: daily, at the same time. Effects typically appear after 2 to 4 weeks. For seasonal depression — throughout the dark season.
Light therapy is generally safe. Side effects are rare: mild headache or a feeling of "warmth" in the first few days, occasionally excessive alertness if used in the evening (which is why evening use is not recommended). In bipolar disorder — only under medical supervision, as it can trigger hypomania.
Light therapy is a simple, safe, and effective tool that is frequently underused. For many people, it is the difference between "surviving" the winter months and actually feeling well.
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This article is for informational and educational purposes only. It is not a substitute for professional psychological advice, diagnosis, or treatment. If you are in a crisis situation, please reach out to a qualified mental health professional or a crisis helpline.