It’s been getting darker earlier and earlier, and evenings are about to feel even longer with the end of daylight-saving time on Sunday — a shift that for many seems to exacerbate or accelerate feelings of seasonal depression.
There isn’t comprehensive research on how “falling back” an hour affects people with seasonal affective disorder, a type of depression often linked with light levels. One 2017 Danish study found an 11% increase in hospital visits for depression in the 10 days after the fall time change, but didn’t distinguish between SAD and other kinds of depression.
In general, though, the annual time change does coincide with the time of year that people with SAD feel symptoms more acutely. And many people who don’t have a formal diagnosis of SAD or depression also report feeling “a little more blue,” said doctors who specialize in mood disorders and sleep medicine.
“With daylight hours decreasing inherently with the season shift, separate from daylight-saving time, that definitely means people with SAD are starting to get affected by it right now,” said Dr. Kristin Raj, co-chief of Stanford’s mood disorders clinic and an associate professor of psychiatry and behavioral sciences.
It’s hard to determine whether the shift back to standard time helps or worsens SAD overall. On one hand, there’s more light in the morning, which is thought to help some people. On the other hand, it gets darker earlier, so some may feel less motivated to go out and do things, which could exacerbate their symptoms since physical movement helps boost serotonin and combat depression.
“So it depends on which part of the day we’re looking at that may help or worsen the symptoms of depression with seasonality,” said Dr. Kin Yuen, a UCSF sleep medicine specialist.
It’s not entirely clear why light affects mood, but it’s likely linked to the impact light has on the circadian rhythm, the body’s 24-hour internal clock.
“Light is what resets people’s circadian rhythms,” Raj said. “There’s something about the circadian rhythm that impacts mood as well.”
It’s also not clear why getting exposure to morning light, as opposed to afternoon or evening light, can help SAD. But it may be related to when the body naturally produces melatonin, the hormone that signals it’s time to sleep. Melatonin levels peak in the evening, “so there’s something about getting light 10 to 12 hours after those peak melatonin levels that really helps shift your circadian rhythm to realize it’s morning and this is the time to be waking up,” Raj said.
Those with SAD or those who struggle with adjusting to the time change may find that getting exposure to natural light or artificial light of a certain intensity in the morning helps.
That could mean taking a 10 to 20 minute outdoor walk in the morning. Or, if it’s hard to get out of the house, bright light therapy for about 20 minutes — light bulbs with at least 10,000 lux, a measurement of their intensity — has been shown to help people acclimate.
Dawn simulation light therapy also can help reset circadian rhythms and boost mood, Raj said. This consists of lights that gradually brighten ahead of normal wake-up time.
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Rachel Carter is a health and wellness expert dedicated to helping readers lead healthier lives. With a background in nutrition, she offers evidence-based advice on fitness, nutrition, and mental well-being.
