- Research shows daylight savings time can have a substantial, yet short-term impact on sleep.
- Seasonal changes may also result in mood changes and seasonal affective disorder (SAD).
- To adjust to a new wake and sleep time, maintain a consistent sleep schedule and change gradually until your body syncs up with the new time.
On Sunday, November 3, most people in the United States will set their clocks back one hour as daylight saving time (DST) ends.
During the fall and winter, when the days are shorter, the body’s internal clock may become disrupted due to a lack of exposure to sunlight. This may lead to the symptoms we know as seasonal depression or seasonal affective disorder (SAD).
In addition to mood changes, daylight savings time may also disrupt sleep. A
Daylight savings time impacts quality sleep and can also influence mood, alertness, and appetite. Here’s what you need to know.
The human body has an internal clock, or circadian rhythm, that cycles through daily periods of sleep and wakefulness.
“In mammals, including humans, the strongest time signal is light,” Sara Benjaminn, MD, a clinical associate with the Department of Neurology at the Johns Hopkins School of Medicine, told Healthline.
“The system that coordinates our sleep-wake rhythm is the suprachiasmatic nucleus, which receives light input from photosensitive retinal ganglion cells and then sends signals to other regions of the hypothalamus to regulate the timing of different body systems, including when different hormones are released, when we want to eat, and when to sleep or be awake,” Benjamin explained.
Nancy Foldvary-Schaefer, DO, director of the Sleep Disorders Center in Cleveland Clinic’s Neurological Institute, explained that human beings have a pacemaker (the suprachiasmatic nucleus) that regulates circadian rhythms in the brain and maintains a 24-hour cycle through a pathway involving the retina, which is sensitive to light and dark.
Light stimulates wakefulness and dark stimulates sleep pathways and the release of melatonin, which is an endogenous hormone that promotes sleep.
The body’s internal clock is set based upon our exposure to sunlight.
When light enters our eyes, it sends the message to our brain that it’s time to wake up. When it’s dark outside, a hormonal signal is sent to our brain that it’s time to sleep.
People who experience winter depression or seasonal affective disorder are already prone to disturbances in their body clock. It’s thought that time changes could make depression worse by disrupting the body clock even further.
A 2017 study found an 11% increase in depressive episodes during the switch from daylight saving to standard time.
While seasonal affective disorder can be difficult to navigate during the darker winter months, treatment options are available, such as:
- medications (i.e. SSRIs)
- psychotherapy
- light therapy
Reducing your risk for seasonal depression
- Begin treatment early.
- If possible, plan to travel to a sunnier location when you’re most prone to depression.
- Get out and walk in the morning sunlight.
- Don’t be afraid to ask for help if you need it.
The change in seasons may affect mental and physical health in various ways.
“Seasons bring changes in light and temperature that affect activity levels and mood,” Foldvary-Schaefer said. “In the realm of sleep and brain function, shorter, darker, and colder days tend to bring more sadness and can worsen depression.”
Physically, this also can lead to more daytime sleepiness and fatigue, major symptoms of sleep disorders.
People with insomnia and hypersomnia tend to feel better in the summer months. Sunlight also stimulates vitamin D production, which is important for immunity, Foldvary-Schaefer explained.
In addition, circadian misalignment may cause changes in sleep, cognition, mood, metabolism, immune health, cardiac function, and muscle strength.
“Summer is a time of bright daytime light and outdoor activities; this increases exposure to daytime light and promotes robust circadian alignment,” Melissa Knauert, MD, PhD, associate professor of pulmonary medicine at Yale School of Medicine, told Healthline.
“Winter is a time of more limited daytime light and indoor activities which exacerbate the loss of exposure to daytime light; this loss of light weakens the circadian system’s alignment and thus contributes to dysfunction at the organ level,” Knauert noted.
Nearly 50% of people in the U.S. are
“Everyone has an individual sleep need and circadian predilection, Foldvary-Schaefer said, noting that some people may naturally be “night owls” and prefer the darker days.
When the time falls back, we gain an hour of sleep, which may be helpful for many people. However, Foldvary-Schaefer explained that sleep disturbances more often occur in the spring when we add an hour of sleep loss to a chronically sleep-deprived state.
Interestingly,
Shift workers face their own challenges, as their wake time is often against the human condition, making time shifts an added challenge, Foldvary-Schaefer noted.
“Most people adapt better to the ‘fall back’ to standard time than they do to daylight savings time, although they like having more daylight in the evening for evening activities,” Benjamin said. “They get an extra hour of sleep with this time change, and there is lighter in the morning, which is helpful for people to be more alert in the morning.”
Still, with either time change, there can be an uptick in sleep disruption and mood changes. Some people may be less inclined to go back out after work if it is dark, for example, and that may impact mood as they have changes in social interactions, Benjamin explained.
Standard time aligns with most people’s circadian rhythm much better than daylight savings time, so many people sleep less during daylight savings time. They may stay up later due to more hours of light and have more trouble waking up at the desired time for work and school, Benjamin added.
When the days become shorter, there are several ways to make the transition as smooth as possible.
Exposure to natural light during the day, such as sitting near a window at lunch or going outside for a short walk, can be helpful, Benjamin said.
“The spring transition to daylight savings time means it is darker in the morning, so they may need to allow extra time to make sure that they are alert in the morning before driving, for example, exercising at home,” Benjamin noted.
“If people have trouble falling asleep in the evening, especially people who need an early bedtime due to an early wake time for work, we suggest wearing sunglasses when going outside in the evening.”
According to Knauert, promoting overall sleep health is one of the best ways to build resilience to the changes between standard and daylight savings time. This includes strategies such as sleeping at least 7 hours per night and maintaining a consistent sleep schedule throughout the week. The key is to make the switch gradually.
Knauert suggested going to bed 5 to 10 minutes later each night starting a week before the end of daylight savings time.
The end of daylight saving time can result in numerous health changes, most notably disruptions in sleep and mood changes like seasonal depression.
Humans have a circadian rhythm that is directly impacted by light. When the seasons change, it can take time for the body to adjust.
To adapt to changing the clocks, experts suggest a regular sleep schedule and going to bed a few minutes later each night to compensate for the hour difference.
