A man and a dog walk Sunday, February 11, 2018, at Kereiakes Park. Spending time outdoors during the winter may help reduce symptoms of seasonal affective disorder. (Bac Totrong/photo@bgdailynews.com)

It’s not just the “winter blues.”

Seasonal affective disorder, or SAD, is a weather-dependent form of depression that occurs primarily in the fall and winter months. About a half-million people in the U.S. suffer from winter SAD, and another 10 to 20 percent suffer from a more mild form of winter depression, according to the Cleveland Clinic, a nonprofit academic medical center.

In recent years, diagnoses of the disorder have become more common, according to Dr. Joseph Grau, a psychiatrist at The Medical Center at Bowling Green.

“The rate of seasonal affective disorder probably hasn’t changed over the last 100 years,” Grau said, but there are more diagnoses now because “people have become increasingly aware of the seasonal nature of depression for some people.”

Jonathan Lee, a licensed marriage and family therapist at More to Life Counseling in Bowling Green, also treats seasonal affective disorder.

“I think it’s very common, more common than people believe,” Lee said. “Over half of the population suffers from seasonal depression at some point. Some people just manage it better than others.”

It’s easy to mistake weather-related moods with seasonal depression. During the past month, Bowling Green received more than 11 inches of rain, so many people probably remained indoors more than normal. That can make people feel gloomy and constrained but not necessarily clinically depressed, according to Grau.

Seasonal winter depression extends beyond a depressed mood with symptoms such as low energy, hypersomnia, overeating, weight gain, carbohydrate cravings and social withdrawal, such as a loss of interest in usual activities.

Though less common, some people experience season-related depression during the summer. These folks might experience low appetite, insomnia, agitation, restlessness, anxiety and episodes of violent behavior, according the National Institute of Mental Health.

The causes of SAD are unknown. But there are biological clues to why people might feel sleepier or have delayed circadian rhythms during shorter sunlight days.

Darkness increases people’s production of the sleep-regulating hormone melatonin, and people produce less vitamin D, which plays a role in serotonin activity, with limited exposure to sunlight, according to NIMH.

Seasonal depression treatments commonly involve LED-light devices, vitamin D supplementation, cognitive behavior therapy, antidepressants, melatonin and spending time outdoors.

In Lee’s experience, seasonal depression among the local population has been strongly associated with a deficiency in vitamin D. That’s why his first recommendation to people displaying symptoms of SAD is to get tested for a deficiency – and begin supplementation with vitamin D3 if necessary. In the past few years, only a handful of patients had normal levels of at least 50 or 60 nanograms per milliliter, according to Lee.

“We’re not outside a whole lot,” Lee said. “We get D3 from the sun and very few foods.”

Vitamin D supplementation by itself is not regarded as an effective treatment for seasonal depression, according to NIMH.

Medications such as selective serotonin reuptake inhibitors, which is a form of antidepressant, is a common treatment method. Medications are especially helpful when a SAD patient has sleep disturbances, according to Grau. But the pills can have some problematic side effects – and people react differently to certain medications.

Cognitive behavior therapy, which More to Life Counseling and most psychiatrists offer, can help people identify activities that promote pleasure and positive emotions and is considered an effective treatment for SAD.

“Psychotherapy has an important place for the treatment of patients,” Grau said. “Depression is like any other health problem … there are psychological consequences.”

In 2008, the Food and Drug Administration approved physicians to perform a new form of depression therapy called transcranial magnetic stimulation, which is a noninvasive form of brain stimulation. Repetitive treatments have shown to be well-tolerated compared to alternatives such as antidepressants.

“I would offer the opinion that seasonal affective disorder is in fact a form of major depressive disorder,” Grau said, so neurostimulation is a “reasonable option.”

The Medical Center offers transcranial magnetic stimulation, or TMS.

“We’ve seen good results with TMS, for major depressive and seasonal affective disorder,” Grau said.

Light therapy is potentially the most important treatment method for some SAD patients. Light therapy lamps, which can cost $40 or $400, mimic sunshine and provide the full spectrum of light. For 35 to 45 minutes a day, people can set the devices next to them while reading a book or working in the office.

“For people with SAD, it can make a huge difference,” Grau said, but “it either works very well or doesn’t work at all.”

Some scientists also advocate fitting in more time outdoors in the actual sunshine and in nature as often as possible in the winter for multiple mental benefits.

“It’s certainly helps people to be out in the sunshine with fresh air, getting exercise,” Grau said, because it helps minimize the effects of depression by improving mood. “I don’t think it can do anything but help to be outside.”

The farther someone lives from the equator – Bowling Green sits about 2,500 miles away – the shorter the winter days, and the more likely they will experience seasonal affective disorder.

“It’s helpful to understand the beneficial impact of sunlight on mood,” Grau said.

People might recognize that they feel better when it’s sunny or if they travel to somewhere sunny, but perhaps misunderstand seasonal affective disorder, according to Lee.

“We dismiss it way too often,” Lee said, or adopt the mentality that “I’ll feel better in April.”