If the onset of winter makes you feel like hibernating due to sadness, don’t just grin and “bear” it. Instead, take steps to feel healthy and energetic all winter long.

It’s normal to have an occasional bout of the winter blues and yearn for the sunny days of summer. But if you experience long stretches of feeling down or being unusually fatigued and irritable, find yourself withdrawing from social events or activities you used to enjoy, or start gaining weight due to carb cravings, you may have seasonal affective disorder (SAD), a form of depression.

Your doctor may diagnose you with SAD based on these symptoms, especially if you’ve had the same pattern of symptoms for at least three consecutive winters and your symptoms vanish completely in the sunnier months.

Some 5 to 20 percent of Americans experience SAD, which can range from mild to severe, according to the American Academy of Family Physicians. About three out of four are women. SAD often begins between ages 18 and 30 and tends to strike people who live in northern parts of the United States more than those in the south. About 10 percent of Alaskans have been diagnosed with SAD compared to only about 1 percent of Floridians according to the National Institutes of Health (NIH).

The exact cause of SAD is unknown. Some research suggests it results from shifts in your circadian rhythms (your internal body clock) when you are exposed to less sunlight, along with changes in the balance of certain brain chemicals, especially serotonin and melatonin.

Turning SAD to glad

Small tweaks to your daily routine and simple at-home treatments can help you prevent or minimize SAD and feel better even when the sun isn’t shining.

The sooner you start, the better. “In the late fall, you probably winterize your car and your home, but you should winterize yourself, too,” says Ani Kalayjian, Ed.D., adjunct professor of psychology at Teachers College, Columbia University in New York. “If you know you are susceptible to symptoms of SAD in the winter, you should prepare ahead of time to prevent those symptoms.”

Kalayjian offers these strategies.

1. See the light. Less sunlight means more SAD, so it’s not surprising that exposing yourself to bright light can make you feel better. Get outside as much as possible in the winter. Also, talk to your doctor about light therapy. It involves sitting in front of a therapeutic light box that simulates strong sunlight each morning for about 30 minutes. About 70 percent of people diagnosed with SAD can get better with light therapy within a few weeks, according to the NIH.

2. Depend on D. Ask your doctor if you should take vitamin D supplements. He or she may want to test your blood levels. Your skin manufactures D in the presence of sunlight. Recent research indicates that people who live in less-sunny climates can have too-low levels of D in the winter, and that taking vitamin D supplements may have many health benefits, including warding off symptoms of SAD. “We don’t know exactly how vitamin D might prevent SAD, but research shows it may help maintain levels of serotonin in the brain,” says Kalayjian.

3. Exercise. You may be tempted to crawl back into your warm bed rather than don workout clothes, but exercising in winter is key to beating SAD. When you exercise, your body releases endorphins, natural feel-good chemicals that can lift your mood. “Exercise for at least 30 minutes every day,” suggests Kalayjian. “Sign up now for an exercise class, join a gym, call up a friend or neighbor and set a standard time to meet and exercise together, or do whatever works to keep you motivated to exercise.” When possible, exercise outdoors to get the additional mood-lifting benefits of natural sunlight and fresh air.

4. Take a deep breath. Yoga, meditation, tai chi, and relaxation exercises all encourage you to take deep, diaphragmatic breaths. “The oxygen in your breath acts as a relaxer, which is helpful in fighting SAD,” says Kalayjian. Deep breathing exercises have been shown to trigger the body’s relaxation response, characterized by slower breathing, reduced blood pressure and a feeling of calm and well-being, according to the NIH’s National Center for Complementary and Alternative Medicine.

Experts at Harvard Medical School recommend this one-minute deep-breathing exercise: Place one hand on your lower belly. Breathe in slowly. Pause for a count of three, then breathe out. Pause for a count of three again. Continue for one minute. The hand on your belly should move every time you inhale and exhale.

5. Try some anti-SAD foods. Many people with SAD crave carbs, but giving in to those urges can ultimately make you feel worse. Instead, stock your refrigerator and pantry with healthy, mood-boosting foods including green, leafy vegetables and berries. These are high in antioxidants, which some research suggests might help reduce depression and anxiety.

Eating foods rich in omega-3 fatty acids, such as salmon and trout, may also reduce your risk for depression and even help you concentrate.

6. Consider talking to a counselor or therapist. Studies indicate that one form of therapy, known as cognitive behavioral therapy, can improve SAD symptoms when used alone or in combination with light therapy.

7. Skip the wine. Limit your consumption of alcohol or don’t drink it at all if you are battling SAD. Over time, excessive drinking can increase your risk for depression and anxiety according to the Centers for Disease Control and Prevention.

8. Plan a vacation in the sun. Easier said than done, especially on a limited budget, but there is good evidence that a week in the tropics in the dead of winter can have long-lasting mood-lifting effects. One possible reason is that a tropical vacation can give you a big dose of vitamin D. “Some people with SAD find if they can go to a warm, sunny climate for a week or two in the winter, they feel much better for several months,” says Dr. Kalayjian.

9. Talk to your doctor. If your symptoms persist or worsen, and especially if you begin to have thoughts about suicide, seek help right away. You may be experiencing an unusually severe case of SAD or another type of depression. Your doctor can prescribe an antidepressant or other kind of treatment that can help you.