Among the symptoms of SAD are sadness, low energy, fatigue, losing interest in activities we once enjoyed, changes in appetite, weight and sleeping patterns, and social withdrawal.
CNN  — 

Does the wintertime make you want to hibernate like a bear?

If you’ve ever felt less energetic, less motivated, in a bad mood, and less inclined to socialize as the nights get longer and the days grow shorter, know that these feelings are shared by many.

Seasonal affective disorder, or SAD, is a form of recurrent depression with a seasonal pattern that occurs more frequently the farther people live from the equator, most typically during the colder months of the year. The winter blues are said to peak on the third Monday in January – sometimes called Blue Monday – but of course feeling low isn’t confined to just one day.

Among the symptoms of SAD are sadness, low energy, fatigue, losing interest in activities we once enjoyed, changes in appetite, weight and sleeping patterns, and social withdrawal.

A widespread problem

While SAD is more prevalent among women in their fertile years, it affects both men and women.

Five percent of Americans experience SAD in its “syndromal” form – where symptoms can severely impact a person’s ability to function, according to Dr. Norman Rosenthal, a clinical professor of psychiatry at Georgetown University School of Medicine and author of the book “Winter Blues.”

About 15% more Americans deal with its “subsyndromal” form, where symptoms may not be severe enough for a diagnosis, Rosenthal said. In the US, “1 in 5 people are having some trouble with the winter,” he added.

A pioneer in the research on SAD, Rosenthal first described and diagnosed the disorder in the 1980s after observing his own shift in mood and energy when he moved from Johannesburg, South Africa, to New York City in 1976.

The extended period of darkness brought about by the end of daylight saving time caught him by surprise. “I was dragging. I wasn’t exuberant like I had been,” Rosenthal explained.

“I struggled through until the spring, and then the energy came back. This happened for three straight years.”

What causes SAD?

The causes of SAD are still a topic of debate in the scientific community.

Rosenthal listed biological vulnerability (such as genetics and gender), reduced environmental light and stress as causes for the disorder.

Rosenthal explained that people with SAD need a higher intensity of light to feel energized in winter, as evidenced by their abnormal winter melatonin secretion patterns. Melatonin is a hormone involved in the regulation of our sleep-wake cycle.

Serotonin, a neurotransmitter that affects mood, is also frequently named in the conversation around SAD and its underpinnings.

“There is evidence that brain serotonin varies seasonally, decreasing as the day length shortens. There is also evidence that bright light shining on the eyes gets transformed into nerve signals that stimulate serotonin transmission in parts of the brain responsible for regulating mood,” Rosenthal explained.

“One hypothesis is that these serotonin pathways are affected in people with SAD such that they don’t work as efficiently when there is not enough light around,” he added.

Other experts believe we just don’t know enough about the neurochemical factors influencing SAD.

“We don’t know how mood is regulated by the brain, despite many decades of research. Consequently, we do not know what causes SAD,” said Dr. Paul Desan, associate professor of psychiatry and director of the Winter Depression Research Clinic at the Yale School of Medicine.

While there’s more to be learned about the causes of SAD, important strides have been made in how to treat it, and raising awareness on those options is key, according to Desan.

“I think this is a major public health problem and most people still are very ignorant about treatment opportunities,” he said.

Because feeling crummier during the winter is such a commonplace experience, Desan thinks that can cause people to take SAD less seriously.

“But some people really do have very important changes in how they feel in the winter, and we really would like to get the word out,” he added.

How to treat SAD

For many SAD patients, bright light therapy is a very effective treatment. As little as 30 minutes of exposure per day makes a significant difference, Desan said.

“We advise people to be in 10,000 lux,” a measure of bright light comparable to being outside on a sunny day in July, he explained.

“It’s clear that the treatment is more powerful in the morning than at any other time of the day, so we recommend people do it as early as possible, and certainly before 8 a.m.,” he said.

“We advise people to do it seven days a week. With a few weeks of that kind of treatment, the vast majority of people with seasonal affective disorder are 100% better,” Desan added.

While there are plenty of options on the market for light boxes that promise to help make the winter blues go away, not all devices are created equal. Many of them are too small or too dim.

In a 2019 study, Desan and colleagues tested 24 devices with three criteria in mind: they should produce at least 7,000 lux at a reasonable distance, they should still provide at least 5,000 lux if the user’s head moved 6 inches (15.2 centimeters) in another direction, and they should obtain an acceptable rating from users in terms of glaring and adequate diffusion.

They found three large light boxes that met their criteria, as well as three smaller units (with smaller devices, users might have to adjust their distance from the light source to reap the full benefits). Their picks can be found on the Winter Depression Research Clinic’s website.

“The problem is the FDA doesn’t regulate these light devices,” Desan said. “That means a lot of companies have produced really crappy things that are really just a waste of people’s money,” he added.

If you have a retinal disease, or a medical condition like diabetes that can cause retinal disease, Desan recommends talking to your eye doctor before trying bright light therapy.

Light therapy might not be sufficient in some cases or might not be a good fit for some.

Rosenthal said additional effective ways to treat SAD are medication and talk therapy, “especially if the person uses a cognitive behavioral approach, which has been shown to be effective.”

He also emphasized the importance of staying active (exercising, going outside for walks during the daylight hours) and staying social.

“Don’t burrow in like a bear. Keep active and remember that how you behave is going to affect how you feel,” Rosenthal advised.

In any case, and especially if you are treating depression, you should consult with a mental health professional to get an accurate diagnosis and the best approach for you.