As winter approaches and daylight hours grow shorter, people prone to seasonal depression can feel it in their bodies and brains.

“It’s a feeling of panic, fear, anxiety and dread all in one,” said Germaine Pataki, 63, of Saskatoon, Saskatchewan.

She’s among the millions of people estimated to have seasonal affective disorder, or SAD. Her coping strategies include yoga, walking and an antidepressant medication. She’s also part of a Facebook group for people with SAD.

“I try to focus on helping others through it,” Pataki said. “This gives me purpose.”

People with SAD typically have episodes of depression that begin in the fall and ease in the spring or summer.

Changing the clocks back to standard time, which happened this past weekend, can be a trigger for SAD.

A milder form, subsyndromal SAD, is recognized by medical experts, and there’s also a summer variety of seasonal depression, though less is known about it.

In 1984, a team led by Dr. Norman Rosenthal, then a researcher at the National Institutes of Health, first described SAD and coined the term.

“I believe that because it is easy to remember, the acronym has stuck,” he said.

What causes seasonal affective disorder?

Scientists are learning how specialized cells in our eyes turn the blue wavelength part of the light spectrum into neural signals affecting mood and alertness.

Sunlight is loaded with the blue light, so when the cells absorb it, our brains’ alertness centers are activated and we feel more wakeful and possibly even happier.

Researcher Kathryn Roecklein at the University of Pittsburgh tested people with and without SAD to see how their eyes reacted to blue light. As a group, people with SAD were less sensitive to blue light than others, especially during winter months. That suggests a cause for wintertime depression.

“In the winter, when the light levels drop, that combined with a lower sensitivity, might be too low for healthy functioning, leading to depression,” Roecklein said.

Does light therapy help?

Many people with SAD respond to light therapy, said Dr. Paul Desan of Yale University’s Winter Depression Research Clinic.

“The first thing to try is light,” Desan said. “When we get patients on exposure to bright light for a half an hour or so every morning, the majority of patients get dramatically better. We don’t even need medications.”

The therapy involves devices that emit light about 20 times brighter than regular indoor light.

Research supports using a light that’s about 10,000 lux, a measure of brightness. You need to use it for 30 minutes every morning, according to the research. Desan said this can help not only people with SAD but also those with less-severe winter blahs.

Special lights run from $70 to $400. Some products marketed for SAD are too dim to do much good, Desan said.

If your doctor diagnosed you with SAD, check with your insurance company to see if the cost of a light might be covered, Desan suggested.

What about talk therapy or medication?

Antidepressant medications are a first-line treatment for SAD, along with light therapy. Doctors also recommend keeping a regular sleep schedule and walking outside, even on cloudy days.

Light therapy’s benefits can fade when people stop using it. One type of talk therapy — cognitive behavioral therapy, or CBT — has been shown in studies to have more durable effects, University of Vermont researcher Kelly Rohan said.

CBT involves working with a therapist to identify and modify unhelpful thoughts.

Working with a therapist can help people take small steps toward having fun again.