Hello Darkness, My Old Friend
By: Dana G Smith
Tags: Psychology, Winter, Serotonin, Seasonal Depression

Hello Darkness, My Old Friend

Why your brain is so SAD

Image: Fertnig/Getty

This is a modified excerpt from Inside Your Head 🧠, a weekly newsletter exploring why your brain makes you think, feel, and act the way you do, written by me, Elemental’s senior writer and a former brain scientist. Subscribe here so you won’t miss the next one.

I’ve been feeling a little sad lately. I’ve never been a winter person, but this year, with no holiday parties or vacations to lighten the mood, the short, cold, gray days feel particularly bleak. Not to mention the layer of grief and fear that comes from the tenth month of a pandemic that’s killing more than 2,000 Americans every day. (Aren’t you glad you decided to read this uplifting article?!)

I also know, however, that this feeling isn’t really me — or at least it’s not my normal state of being for nine months out of the year. It’s seasonal affective disorder (SAD!), with some pandemic fatigue and despair sprinkled on top.

Seasonal affective disorder afflicts 5% of U.S. adults, although numbers vary depending on geography. For example, nearly 10% of people in Alaska experience SAD, whereas the prevalence in Florida is only 1.4%.

SAD is more than just the winter blues, writes Ashley Laderer in an Elemental article on seasonal affective disorder from last winter. “It’s typically a repetitive mood cycle where each year, as fall and winter come along, the person starts to experience depressive symptoms — low mood, anhedonia [inability to feel pleasure], poor concentration, sense of guilt or worthlessness, changes in appetite and weight, and changes in sleep,” says Paraskevi Noulas, PsyD, a clinical assistant professor in the department of psychiatry at NYU Langone Health.

Scientists think that seasonal depression is linked to changes in your circadian rhythm — the 24-hour internal clock that dictates many of your hormone levels and, as a result, your energy levels throughout the day. Morning light triggers the start of the cycle each day by activating light-sensitive cells in the suprachiasmatic nucleus (SCN) — a group of about 10,000 neurons in the brain that act as the body’s pacemaker. In the winter, weaker sunlight, less time outside, and shorter days can deprive the SCN of those important light cues, throwing off the body’s schedule.

One of the first and most important steps in your daily circadian rhythm, triggered by morning light, is suppressing the production of the sleep hormone melatonin. Some research suggests that people who experience SAD have either a longer or a delayed melatonin period during the winter. As a result, it can be harder to get out of bed in the morning and you may feel groggy throughout the day.

Levels of the neurochemical serotonin also fluctuate with the seasons, with the lowest levels occurring in December and January. Serotonin is strongly implicated in depression, and most antidepressant drugs work in part by increasing levels of the neurochemical in the brain. Sunlight also seems to affect serotonin activity, although scientists aren’t exactly sure how. It could be that in people with SAD, low light results in more serotonin being sucked back up into brain cells. Another theory is that cells require vitamin D to produce serotonin, and so low vitamin D levels from a lack of sunshine result in less serotonin being made.

The most common treatment for seasonal affective disorder is light therapy. Using a “SAD lamp” in the morning is supposed to help kick-start your circadian rhythm by substituting a bright, white, artificial light for the sun. The support for SAD lamps’ efficacy at treating seasonal affective disorder is growing, and the consensus seems to be that they won’t hurt you and they may help, so you might as well try it. You could also try forcing yourself to go for a walk first thing in the morning.

Interestingly, some of the coldest, darkest places on Earth, like Iceland and Norway, have the lowest rates of seasonal affective disorder. This may be because of genetic variations that protect people there from the negative psychological effects of darkness. (Scientists think SAD may be tied to your genes.) Or it could be due to a shift in mindset. Ardsheer Ali writes in Elemental that rather than dreading the winter, residents of Tromsø, Norway, located north of the Arctic Circle, await its arrival with excitement, and their positive attitude about the season is tied to their well-being.

They look forward to ski season and the shelter of home. Koselig — the Norwegian term for coziness — is a notion widely embraced across the island. Norwegians find a wonderful warmth in snuggling up under the covers when the world outside is frozen. [Among Norwegians,] having a positive wintertime mindset was associated with greater life satisfaction. Participants who agreed more with the positive statements [about the season] reflected signs of better mental well-being during the dark winter.

Let it snow, let it snow, let it koselig.