Afternoon light box is a solid backup, not the star player

Using a light box in the afternoon for late-winter SAD can help, but it’s not as effective as morning use and comes with a sleep-timing trade-off.

Morning light therapy is the gold standard because it shifts your circadian rhythm earlier — exactly what you need when winter has you waking up in the dark and feeling sluggish all day. Afternoon light still boosts mood, serotonin, and alertness, which is real. That afternoon slump? Light box can crush it.

The downside: too much light late in the day can push your body clock later, making it harder to fall asleep. If you’re doing afternoon sessions, keep them before 3 or 4pm, and don’t go longer than 30 minutes. Some people are more sensitive than others.

For late-winter SAD specifically, the sun is coming back, so you might not even need a light box at all if you can grab a real daylight walk around lunch. But if you’re stuck indoors or the gray won’t lift, afternoon light is better than nothing.

Just don’t make it your first choice. Morning still wins.