Seasonal Affective Disorder and Sleep, Part 1

(December 12, 2023) — Many people talk about not liking winter or having the winter blues, but Seasonal Affective Disorder is much more serious.

What Is Seasonal Affective Disorder?

“SAD is a type of clinical depression that comes and goes with the seasons, at about the same time every year,” said Dr. Anuj Chandra, medical director of the Advanced Center for Sleep Disorders. “For some people, it’s so serious that they are clinically depressed for half of the year.”

For most people who suffer from it, SAD begins in the late fall or early winter when the days get shorter, but smaller numbers of people have seasonal depression in the spring and summer.

Up to 10 percent of people in the United States are thought to have SAD, depending on where they live. For example, surveys show that SAD affects 9.7 percent of people in New Hampshire but only 1.4 percent in Florida. It affects women more than men and becomes more common the further north you go.

How SAD Works

SAD affects people most often during the fall and winter because the amount of sunlight during the day is lower. Sunlight is a major influence on your body’s circadian rhythms, the “internal clock” that sets the timing for many body functions.

Normally, darkness at night signals your brain that it is time for your body to slow down, and bright sun the next morning tells your brain that it’s time for your body to wake up and be alert. In the fall and winter, we get shorter days with fewer hours of sunlight so the body’s internal timing is thrown off.

Experts are not certain why it works that way. One theory is that the way your body produces melatonin changes. Usually, melatonin increase at night to promote sleep then fall in the morning, which helps you wake up. For people with SAD, however, melatonin levels peak later at night and last longer in the morning, making it harder to wake up, causing fatigue during the day, and making it hard to fall asleep at night.

SAD and Sleep

Sleep problems are common for people with SAD, including:

• Excessive sleepiness during the day
• Sleeping two hours or more longer at night, compared to the summer months
• Difficulty waking in the morning
• Frequent nightmares

“SAD creates a persistent pattern of disturbed sleep,” said Dr. Chandra. “It can be a never ending cycle of insomnia, poor sleep, and fatigue. All of that makes depression worse.”

The effects can be mild, but for some people, the effects are much more extreme: strong sadness, fatigue, hopelessness, lack of interest in normally enjoyable activities, and social withdrawal.

How to Recognize SAD

How do you know you have SAD?

Seasonal pattern — Symptoms follow the seasons. SAD typically occurs in the fall and winter, then resolves when the days get longer in spring and summer. Among the small number of people who experience warm weather SAD, the pattern of onset and relief is still seasonal.

Daily symptoms — A SAD diagnosis requires you to experience five symptoms of clinical depression every day over a period of time. If you have fewer symptoms, that doesn’t mean you don’t have a problem, just that you’re not suffering from clinical depression.

Read more about SAD in Part 2, Treatment for Seasonal Affective Disorder.