You probably know the feeling. The clocks change, the mornings go dark, and something in you slows down. Most of us just call it the winter blues.
For a smaller group of people, that slump is heavier and lasts for months. Doctors call it seasonal affective disorder, or SAD.
A new meta-analysis in Journal of Affective Disorders Reports looked at how long people need to stick with light therapy before it actually helps.
Researchers from Taipei Medical University pooled 17 randomized controlled and crossover trials.
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The pattern was clear. Light therapy did ease SAD symptoms, but not right away. Only after about two weeks of daily use did the drop in symptoms reach statistical significance.
The effect at one week did not.
The two-week mark matters for winter mood
That timeline matters because November is exactly when many people start feeling the shift and reach for a light box.
If they expect a quick fix after a few days and do not get one, they often give up.
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The meta-analysis suggests they stop just before the treatment would have started working.
A light box is not a mood switch. It is more like exercise. Short sessions over several days add up before you feel much.
Not ordinary lamps
The devices sold for SAD are not ordinary lamps. The standard dose used in research and in clinical practice is a 10,000-lux light box.
According to the National Institute of Mental Health (NIMH), the person sits in front of a very bright light box every day for about 30 to 45 minutes.
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The Mayo Clinic advises using the box within the first hour after waking up, for 20 to 30 minutes.
Your eyes stay open, but you do not stare into the light. You can read, eat breakfast, or check email while it does its work.
Consistency is the thing the trial data keeps pointing to. One missed morning is fine. A week off probably resets the clock on when you will feel the benefit.
When to call a doctor?
SAD is more common than people assume. The NIMH estimates that millions of Americans experience it, and it hits women more often than men.
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Symptoms usually begin in late fall or early winter and ease as daylight returns in spring.
Low mood, oversleeping, and strong carbohydrate cravings are classic signs.
A persistent sad, anxious, or empty mood that lasts most of the day, nearly every day, for at least two weeks is a signal to speak with a doctor or mental health professional.
Light therapy is one of four main treatments the NIMH lists. The others are talk therapy, antidepressant medication, and vitamin D.
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A doctor can also check whether a light box is safe for you. Certain eye conditions and some medications make bright-light exposure riskier, which is why a quick conversation before starting is worth it.
If you already have a light box sitting in a drawer from last winter, the practical takeaway from the new review is simple.
Set it up this week, use it within the first hour of waking, and mark two weeks on the calendar before judging whether it is helping.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.