Winter solstice, the shortest day of the year, occurs this Saturday, December 21, in the Northern Hemisphere. Many people feel the effects both mentally and physically of less sunlight. You might feel sad, tired or anxious during these dark days but sometimes the “winter blues” can develop into something more serious.

According to Study Finds, when people experience daily, persistent symptoms of mood changes and lethargy, they may be suffering from seasonal affective disorder, or SAD.  About 10 million Americans experience SAD, which is a form of depression that usually affects people from mid to late fall through the early days of spring. “The most common misconception is that it is ‘just’ winter blues and not that big of a deal,” said Dr. Jeff Temple, licensed psychologist and professor at the University of Texas Medical Branch.  “On the contrary, it impacts millions of Americans with symptoms consistent with major depression.”

Experts say that SAD can be potentially triggered by a lack of serotonin, the mood-regulating brain chemical that dims with less daylight. Less exposure to the sun’s rays also reduces vitamin D levels, which support serotonin levels and metabolism.

Dr. Norman Rosenthal, author of Defeating SAD: A Guide to Health and Happiness Through All Seasons, who first described SAD and pioneered the use of light therapy in its treatment, tells Newsmax that several factors contribute to feeling blue in the winter.

“These include a genetic component, stress, and a lack of environmental light,” he explains. “We can feel sad at any time of the year and it’s part of the normal palette of human emotions. For example, we feel sad when we fail to reach a goal, have a setback, or lose someone we love. But SAD is a specific condition that affects people predominantly during the winter months.”

 Your doctor can diagnose SAD with a detailed medical examination and psychiatric evaluation.

Here are some proven therapies to treat SAD:

• Get more light. Rosenthal says you should go outdoors as often as you can. “Even on a winter day you can get a lot of light coming from the sky,” he says. If you can’t get out, he suggests bringing more light fixtures indoors. “You can buy those specially built for treating SAD. The lightbox should be big enough —at least one foot square, made by a reputable manufacturer, and ideally used in the morning or any time of day.” The light boxes give off 10,000 lux which is a unit of illuminance says USA Today. Make sure the boxes are equipped with UV filters to protect your skin and follow the directions carefully. Tanning beds are not effective, say experts.

• Exercise regularly. Physical activity has been shown to boost mood, decrease the symptoms of depression and reduce stress, according to the American Psychological Association. Start slowly and build up to 30 to 60 minutes a day, five days a week. Find an activity you like to do so that you will be more likely to stick with it.

• Try to minimize stress. Rosenthal says we should try to identify our stressors, and if they are unavoidable, figure out ways to deal with them. Very often, being indoors means more screen time so try to limit your exposure to negative news and limit the amount of time you spend staring at a screen.

• Boost your mood with food. Heidi Hanna, a leading psychologist and expert on the mind-body connection, tells Newsmax that choosing foods carefully can curb sugar and carbohydrate cravings throughout the day and help stabilize your mood. “Include a balance of natural sources of complex carbohydrates, lean protein and healthy fat that keep blood sugar levels stable throughout the day. You should also consume a rainbow of produce to provide antioxidants,” she says. Foods rich in vitamin D such as fatty fish, fish oil, vitamin D fortified foods like milk, orange juice, breakfast cereal and yogurt can help the winter blues.

• Psychotherapy. Counseling, especially cognitive behavior therapy, or CBT, may help people with SAD. By learning new ways of dealing with emotions, sufferers can change unhelpful thoughts and behaviors, according to Study Finds. CBT-SAD is a special form of therapy designed to treat people suffering from the disorder that is usually conducted in two weekly group sessions for six weeks. People learn to replace negative thoughts about the season with more positive thoughts.