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As winter transitions into spring, longer days of sunshine and warmer weather can improve one’s mood after a cold winter keeps us inside. However, for some individuals in Philadelphia, this change doesn’t happen right away.
Seasonal affective disorder, or SAD, is a type of depression linked to seasonal changes, typically appearing during fall and winter, when daylight hours decrease. Unlike other types of depression, SAD follows a predictable pattern.
“It has an annual recurrence … typically fall and winter when the days are shorter,” said Dr. George Brainard, professor of neurology at Thomas Jefferson University who directs Jefferson’s Light Research program.
But as spring nears, those feelings of depression don’t always vanish.
“Symptoms are very high still” throughout March, he said. “They begin to reduce in April and May.”
Why is seasonal affective disorder present in early spring?
The delay results from the body’s reaction to changing light. During the winter months, reduced sunlight can disrupt circadian rhythms, often referred to as the body’s internal clock. Less sunlight can also impact hormones like melatonin and serotonin, which regulate sleep and mood.
As daylight increases, those systems take time to adjust. “You get a bright day, you might get a momentary relief [from] the acute effects of light, but you’re not getting the full relief because you’re not fully in the seasonal change yet,” Brainard said. “Your body takes time to reset and re-adapt to the lengthening days.”
The lag in readjusting is most often felt in early spring, especially as temperatures fluctuate and sunny days give way to cold, gray weather.