How the Darker Days Downshift Your Metabolism and Mood

Understanding your connection to the shift in seasons can help you adapt and avoid the winter blues
Oct 4 2022

Along with pretty rust-colored leaves and pumpkin spice lattes, there’s another, less-celebrated hallmark of the fall season—the onset of a mental and emotional slump known as seasonal affective disorder.

Known also by its very appropriate acronym, SAD, this disorder can sometimes be severe enough to significantly disrupt day-to-day functioning.

As temperatures steadily fall and sunset times continue their relentless backward march toward winter solstice, an estimated 10 million Americans, according to Boston University School of Medicine, will suffer symptoms associated with major depression, which could include feeling hopeless or worthless, having low energy and motivation, feeling depressed most of the time, experiencing weight gain, withdrawing from social activities, and having trouble sleeping.

While these symptoms are characteristic of major depression in general, what distinguishes SAD is the seasonal nature of the depression. In most cases, it begins, predictably, with the loss of daylight in the fall, lasts throughout the late fall and winter months, and resolves itself in the springtime with increased amounts of daylight. And while SAD is a serious condition that often results in a clinical diagnosis, millions more experience a milder version of it, known simply as the “winter blues.”

Scientists haven’t identified a single cause of SAD, but several theories exist on just what could be causing the spiral into depression. It’s possible that a single factor or combination of factors could contribute to the development of SAD.

Some research indicates that serotonin, a brain chemical and neurotransmitter that’s long been understood to work as a mood stabilizer, may play an important role in SAD. A review published in 2013 in the European Review for Medical and Pharmacological Sciences, titled “Role of Serotonin in Seasonal Affective Disorder,” concluded that people with SAD have lower levels of serotonin activity than those of the healthy population, and that a “decrease in the level of serotonin directly intensifies this disorder.”

Other studies indicate that exposure to sunlight plays an important role in regulating serotonin production, with levels rising and falling along with increased or decreased exposure to bright sunlight, respectively. This has led to speculation that, in those with SAD, this regulation doesn’t function properly, contributing to lower serotonin levels.

These particular theories have become somewhat more controversial in recent months after a large systematic review published in the Molecular Psychiatry raised significant doubts about the serotonin theory of depression, suggesting more complex factors are involved.

Nonetheless, scientists find quantitative factors helpful in understanding what is happening in the brain and body and have looked at other biochemical elements as well.

For instance, people who suffer from SAD may also produce too much of the sleep-regulating hormone melatonin. According to the Cleveland Clinic, melatonin is naturally produced by the brain’s pineal gland in response to light and darkness, increasing production in low light and decreasing it during times of bright daylight.

In those with SAD, melatonin production, which normally increases over the dark winter months, may rise to abnormally high levels, causing excessive tiredness and low energy. It’s thought that high levels of melatonin, combined with low levels of serotonin, may work together to disrupt the body’s normal circadian rhythms, making it difficult to adjust to seasonal changes in day length.

People suffering from depression are also often low in vitamin D, and researchers speculate that there may be a significant association between the two.

Along with dietary sources of vitamin D, the body produces vitamin D when the skin (without sunscreen) is exposed to sunshine. Since hours of sunlight are greatly reduced during the winter months, and those already struggling with depression may be even less inclined to spend time outdoors, the problem of vitamin D deficiency may be exacerbated.

Also, vitamin D plays a role in promoting serotonin production, so it’s plausible that a falling level of vitamin D, which is particularly common in those suffering from SAD, could further aggravate the effects of low serotonin activity.

It’s worth noting that the shift to sedentary indoor lifestyles has contributed to a significant reduction in sun exposure, which can reduce vitamin D levels, disrupt circadian rhythms and melatonin production, and affect serotonin activity.

One more possible cause of SAD may be that some people carry a biological, or genetic, predisposition to the disorder.

Dr. Norman Rosenthal, a psychiatrist, scientist, and author of the best-seller “Winter Blues,” who first described SAD in the 1980s, told The Epoch Times that there may be a genetic component.

“It’s common for people with SAD to have relatives who also experience similar symptoms,” he said. “Various studies have looked at what are known as candidate genes, which means genes that control various brain processes suspected as being involved in mood regulation. Some of these studies have shown abnormalities in SAD patients compared to healthy controls.

“The conservative position at this time is that SAD probably has a genetic basis, but its exact nature has yet to be fully understood.”

Women between the ages of 20 and 40 tend to experience SAD at far higher rates than men of the same age—four times as often—leading to speculation that there may be a significant link between the dominant female hormones estrogen and progesterone, and a susceptibility to seasonal depression.

Rosenthal cited findings that suggest the cyclical pattern of estrogen and progesterone secretion over a woman’s lifetime could play a role.

“We have observed that when girls enter puberty, they begin to show a greater tendency to develop mood changes with the seasons. This hasn’t been found when boys enter puberty,” he said.

“On the other side of the fertility cycle, after the menopause, women appear to be less susceptible to seasonal mood changes. These observational findings suggest that the cyclical secretion of estrogen and progesterone during the fertile phase of development in women contributes to their tendency to experience seasonal changes and behavior, which, in some cases, may present as the symptoms of SAD.”

It’s important to note that even though researchers are unclear on exactly what may cause SAD symptoms, human beings have likely always experienced seasonal shifts in mood and behavior to some degree.

According to the Cleveland Clinic, between 10 percent and 20 percent of U.S. adults may experience the winter blues, leaving them feeling down in the dumps for a while. It’s when the change in mood, outlook, and behavior is severe and debilitating that there’s a real cause for concern.

Practices to Counter Seasonal Depression

For those suffering under the heavy weight of SAD, or even just feeling down once gray skies and shorter days become the norm, there are several interventions that can help.

Increase Your Exposure to Bright Light

Since SAD is directly related to a decreased exposure to light, it makes sense that the first remedy of choice is to purposefully increase exposure to bright light. We normally think of SAD as being due mainly to decreased daylight hours, but any major shift toward light deprivation can have a depressing impact.

Moving from a sun-drenched state, such as Florida, to Vermont, for example, or from a light-filled home to a darker one, or even from an office with large windows to a basement room can all have an effect. Making your living environment lighter and brighter is a start. Moving your desk or chair next to a window, painting with lighter colors, and using more lamps or other indoor lighting can help. Spend some time outdoors on bright days, even when it’s cold.

When that’s not enough, try light therapy using a light box or dawn simulator. Pioneered by Rosenthal in the 1980s, light therapy has been successfully used to treat SAD ever since.

This therapy involves sitting in front of a light box for a set amount of time (usually between 20 and 90 minutes, first thing in the morning). The light emitted is designed to mimic outdoor light and is about 20 times more intense than ordinary indoor light, while filtering out most UV light.

This exposure to bright light is thought to inhibit the release of melatonin, according to a study published in Sleep Medicine Clinics in 2015.

In general, you want sunlight in the morning and day and to avoid blue light at night so that you can maintain healthy melatonin production.

Healthy Lifestyle Habits

Exercise is well known for its ability to reduce anxiety, improve sleep, and trigger a release in the body of “feel-good” chemicals called endorphins. These benefits are all helpful in treating depression. According to Harvard Health, exercise works just as well as taking antidepressant medication for some people, making it a potentially powerful help.

Also, because people suffering from depression often crave sweet and starchy carbohydrates, opting for healthy, well-balanced meals that include lean protein, vegetables, and complex carbohydrates can help stabilize blood sugar and energy levels.

Spend Time With Others

Researchers from Massachusetts General Hospital identified social connections as being the single most protective factor against depression.

Whether through walks, volunteer work, meeting for tea, or a shared club or activity, spending time with other people can help lift the feelings of loneliness and isolation that often accompany depression. Conversation with other positive people can help to shift the focus away from negative thoughts and put things into perspective.

Talk Therapy (Cognitive Behavior Therapy)

For serious depression, seeking help from a mental health professional may be prudent. Cognitive behavior therapy, in which a therapist helps to break down and identify negative thought patterns and challenge them, has been found to be effective not only in helping current depression, but even in reducing the risk of relapse into depression in subsequent years.

“Cognitive behavior therapy, researched by Kelly Rohan at the University of Vermont, has shown that helping people with SAD work on their automatic negative thoughts and self-defeating behaviors can have a powerfully positive effect,” Rosenthal noted.

While several different therapies for SAD, including antidepressants, have been found to be helpful in treating its depressive symptoms, SAD is a condition that likely has multiple contributing factors and is best helped using several different approaches.

“In my experience, the best results in treating people with SAD come from combining different methods of treatment,” Rosenthal said.

The good news is that, for people suffering from SAD, help is certainly available.

An Ancient Chinese View of Winter Mood Changes

Winter mood shifts are a reflection of the interconnection between human beings and nature, according to traditional Chinese culture.

In the traditional Chinese calendar, the year is broken up into 24 solar terms of about two weeks each. This calendar system is used to help people align with the season and live a harmonious life.

The single largest division this calendar draws in the year is between a yang period comprising the warmer time of the year, and a yin period comprising the cooler part of the year.

The yang energy of the warmer months is expansive. This is the time to grow, socialize, and work. The yin energy of the cooler months is recessive. It’s the time to recede, introspect, and rest.

This perspective informs habits and helps people to understand what they need at different times of the year. For instance, under the guidance of this calendar, January is a terrible time for any resolution requiring an expanse of energy, like taking up a new gym habit. That kind of resolution should be saved for the spring, when the Earth is awakening and you can ride the wave of growing energy naturally occurring at that time.

January is, however, a great time for resolutions that require introspection and self-discovery. The quiet, inward nature of the season lends itself to calm reflection.

It’s possible that those who suffer depression during the winter months, beyond being affected by the lack of sunlight and social activity of the warmer months, are also being compelled to look inward and resolve issues that may more easily escape their attention at other times of the year.

That isn’t to negate any of the other views or issues that come with SAD, simply to offer that winter is naturally a time to draw inward and tend to your inner world.

Zrinka Peters is a freelance writer focussing on health, wellness, and education topics. She has a BA in English Literature from Simon Fraser University in Canada and has been published in a wide variety of print and online publications including Health Digest,, Today's Catholic Teacher, and
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