If you are feeling sad, depressed, and less energetic in the short dark days of winter, you may have seasonal affective disorder, or SAD. SAD is a form of depression that usually starts in the autumn and lasts into the winter.

Six percent of the U.S. population, mostly those who live in northern climates, is affected by SAD. An additional 14 percent suffers from a lesser form of seasonal mood changes, known as winter blues.

What causes SAD?

• The reduced level of sun in fall and winter can disrupt your internal clock.
• A drop in serotonin, a brain chemical that affects your mood.
• The change in season can disrupt the balance of the body’s level of melatonin, which affects sleep patterns and mood.

Symptoms of SAD include:

• Eating more, especially sweet foods and starchy items.
• Weight gain.
• Difficulty waking up in the morning.
• Difficulty concentrating.
• Withdrawal from friends and family.
• Depression during cloudy weather year round, or if confined in a windowless office or basement apartment.
• Decreased productivity in work or school.
• Losing interest in activities.

Here’s Five Ways to Take Control of SAD

1. Light therapy

Known as phototherapy, light therapy involves sitting a few feet from a special light therapy box that exposes you to bright light. Light therapy imitates natural outdoor light. It is believed to cause a change in brain chemicals linked to mood. Light therapy usually begins to work anywhere from a few days to two weeks. Ask your doctor to recommend a high-quality product that’s safe and effective.

2. Psychotherapy, or talk therapy

A health professional can help you identify and change negative thoughts and behaviors that may be making you feel worse. You can learn healthy ways to cope with SAD and how to manage stress.

3. Find Light

Install skylights in your home. Open the blinds or curtains and let the sunshine in. Cut tree branches that prevent sunlight from streaming in your windows. If possible, sit near bright windows at your home and at work. Take a long walk. Take a chair outside or sit on a bench and soak up the sun. Within two hours of waking up in the morning, get some outdoor light, even if it is cloudy outside.

4. Work Out

Get to the gym or exercise at home every day. Not only will you combat stress and anxiety, being fit can lift your spirits and make you feel good about yourself.

5. Get Your Vitamin D

Low levels of Vitamin D have been linked with symptoms of depression. Foods that contain Vitamin D include fatty fish, such as salmon, tuna, and mackerel and fish liver oils, eggs, and fortified milk, juice, and cereal. Ask you doctor about whether you should take a supplement and how much vitamin D is safe for you.

6. Medications

Your doctor may advise an anti-depressant.