Seasonal affective disorder (SAD) is a type of depression that's related to changes in seasons — SAD begins and ends at about the same times every year. If you're like most people with SAD, your symptoms start in the fall and continue into the winter months, sapping your energy and making you feel moody. Less often, SAD causes depression in the spring or early summer.

Treatment for SAD may include light therapy (phototherapy), medications and psychotherapy.

Don't brush off that yearly feeling as simply a case of the "winter blues" or a seasonal funk that you have to tough out on your own. Take steps to keep your mood and motivation steady throughout the year.

In most cases, seasonal affective disorder symptoms appear during late fall or early winter and go away during the sunnier days of spring and summer. Less commonly, people with the opposite pattern have symptoms that begin in spring or summer. In either case, symptoms may start out mild and become more severe as the season progresses.

Signs and symptoms of SAD may include:

• Feeling depressed most of the day, nearly every day
• Losing interest in activities you once enjoyed
• Having low energy
• Having problems with sleeping
• Experiencing changes in your appetite or weight
• Feeling sluggish or agitated
• Having difficulty concentrating
• Feeling hopeless, worthless or guilty
• Having frequent thoughts of death or suicide

Fall and winter SAD

Symptoms specific to winter-onset SAD, sometimes called winter depression, may include:

• Oversleeping
• Appetite changes, especially a craving for foods high in carbohydrates
• Weight gain
• Tiredness or low energy

Spring and summer SAD

Symptoms specific to summer-onset seasonal affective disorder, sometimes called summer depression, may include:

• Trouble sleeping (insomnia)
• Poor appetite
• Weight loss
• Agitation or anxiety

Seasonal changes in bipolar disorder

In some people with bipolar disorder, spring and summer can bring on symptoms of mania or a less intense form of mania (hypomania), and fall and winter can be a time of depression.

When to see a doctor

It's normal to have some days when you feel down. But if you feel down for days at a time and you can't get motivated to do activities you normally enjoy, see your doctor. This is especially important if your sleep patterns and appetite have changed, you turn to alcohol for comfort or relaxation, or you feel hopeless or think about suicide.

The specific cause of seasonal affective disorder remains unknown. Some factors that may come into play include:

• Your biological clock (circadian rhythm). The reduced level of sunlight in fall and winter may cause winter-onset SAD. This decrease in sunlight may disrupt your body's internal clock and lead to feelings of depression.
• Serotonin levels. A drop in serotonin, a brain chemical (neurotransmitter) that affects mood, might play a role in SAD. Reduced sunlight can cause a drop in serotonin that may trigger depression.
• Melatonin levels. The change in season can disrupt the balance of the body's level of melatonin, which plays a role in sleep patterns and mood.

Seasonal affective disorder is diagnosed more often in women than in men. And SAD occurs more frequently in younger adults than in older adults.

Factors that may increase your risk of seasonal affective disorder include:

• Family history. People with SAD may be more likely to have blood relatives with SAD or another form of depression.
• Having major depression or bipolar disorder. Symptoms of depression may worsen seasonally if you have one of these conditions.
• Living far from the equator. SAD appears to be more common among people who live far north or south of the equator. This may be due to decreased sunlight during the winter and longer days during the summer months.

Take signs and symptoms of seasonal affective disorder seriously. As with other types of depression, SAD can get worse and lead to problems if it's not treated. These can include:

• Social withdrawal
• School or work problems
• Substance abuse
• Other mental health disorders such as anxiety or eating disorders
• Suicidal thoughts or behavior

Treatment can help prevent complications, especially if SAD is diagnosed and treated before symptoms get bad.

Even with a thorough evaluation, it can sometimes be difficult for your doctor or mental health professional to diagnose seasonal affective disorder because other types of depression or other mental health conditions can cause similar symptoms.

To help diagnose SAD, your doctor or mental health professional may do a thorough evaluation, which generally includes:

• Physical exam. Your doctor may do a physical exam and ask in-depth questions about your health. In some cases, depression may be linked to an underlying physical health problem.
• Lab tests. For example, your doctor may do a blood test called a complete blood count (CBC) or test your thyroid to make sure it's functioning properly.
• Psychological evaluation. To check for signs of depression, your doctor or mental health professional asks about your symptoms, thoughts, feelings and behavior patterns. You may fill out a questionnaire to help answer these questions.
• DSM-5. Your mental health professional may use the criteria for seasonal depressive episodes listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), published by the American Psychiatric Association.

Treatment for seasonal affective disorder may include light therapy, medications and psychotherapy. If you have bipolar disorder, tell your doctor — this is critical to know when prescribing light therapy or an antidepressant. Both treatments can potentially trigger a manic episode.

Light therapy

In light therapy, also called phototherapy, you sit a few feet from a special light box so that you're exposed to bright light within the first hour of waking up each day. Light therapy mimics natural outdoor light and appears to cause a change in brain chemicals linked to mood.

Light therapy is one of the first line treatments for fall-onset SAD. It generally starts working in a few days to a few weeks and causes few side effects. Research on light therapy is limited, but it appears to be effective for most people in relieving SAD symptoms.

Before you purchase a light box, talk with your doctor about the best one for you, and familiarize yourself with the variety of features and options so that you buy a high-quality product that's safe and effective. Also ask your doctor about how and when to use the light box.

Medications

Some people with SAD benefit from antidepressant treatment, especially if symptoms are severe.

An extended-release version of the antidepressant bupropion (Wellbutrin XL, Aplenzin) may help prevent depressive episodes in people with a history of SAD. Other antidepressants also may commonly be used to treat SAD.

Your doctor may recommend starting treatment with an antidepressant before your symptoms typically begin each year. He or she may also recommend that you continue to take the antidepressant beyond the time your symptoms normally go away.

Keep in mind that it may take several weeks to notice full benefits from an antidepressant. In addition, you may have to try different medications before you find one that works well for you and has the fewest side effects.

Psychotherapy

Psychotherapy, also called talk therapy, is another option to treat SAD. A type of psychotherapy known as cognitive behavioral therapy can help you:

• Identify and change negative thoughts and behaviors that may be making you feel worse
• Learn healthy ways to cope with SAD, especially with reducing avoidance behavior and scheduling activities
• Learn how to manage stress

Mind-body connection

Examples of mind-body techniques that some people may choose to try to help cope with SAD include:

• Relaxation techniques such as yoga or tai chi
• Meditation
• Guided imagery
• Music or art therapy

In addition to your treatment plan for seasonal affective disorder:

• Make your environment sunnier and brighter. Open blinds, trim tree branches that block sunlight or add skylights to your home. Sit closer to bright windows while at home or in the office.
• Get outside. Take a long walk, eat lunch at a nearby park, or simply sit on a bench and soak up the sun. Even on cold or cloudy days, outdoor light can help — especially if you spend some time outside within two hours of getting up in the morning.
• Exercise regularly. Exercise and other types of physical activity help relieve stress and anxiety, both of which can increase SAD symptoms. Being more fit can make you feel better about yourself, too, which can lift your mood.

Certain herbal remedies, supplements or mind-body techniques are sometimes used to try to relieve depression symptoms, though it's not clear how effective these treatments are for seasonal affective disorder.

Herbal remedies and dietary supplements aren't monitored by the Food and Drug Administration (FDA) the same way medications are, so you can't always be certain of what you're getting and whether it's safe. Also, because some herbal and dietary supplements can interfere with prescription medications or cause dangerous interactions, talk to your doctor or pharmacist before taking any supplements.

Make sure you understand the risks as well as possible benefits if you pursue alternative or complementary therapy. When it comes to depression, alternative treatments aren't a substitute for medical care.

These steps can help you manage seasonal affective disorder:

• Stick to your treatment plan. Follow your treatment plan and attend therapy appointments when scheduled.
• Take care of yourself. Get enough sleep to help you feel rested, but be careful not to get too much rest, as SAD symptoms often lead people to feel like hibernating. Participate in an exercise program or engage in another form of regular physical activity. Make healthy choices for meals and snacks. Don't turn to alcohol or recreational drugs for relief.
• Practice stress management. Learn techniques to manage your stress better. Unmanaged stress can lead to depression, overeating, or other unhealthy thoughts and behaviors.
• Socialize. When you're feeling down, it can be hard to be social. Make an effort to connect with people you enjoy being around. They can offer support, a shoulder to cry on or shared laughter to give you a little boost.
• Take a trip. If possible, take winter vacations in sunny, warm locations if you have winter SAD or to cooler locations if you have summer SAD.

You may start by seeing your family doctor or a mental health professional such as a psychiatrist or psychologist.

Here's some information to help you get ready for your appointment.

What you can do

Before your appointment, make a list of:

• Your symptoms, such as feeling down, having a lack of energy, excess sleeping and appetite changes
• Your depression patterns, such as when your depression starts and what seems to make it better or worse
• Any other mental or physical health problems you have — both can affect mood
• Any major stressors or life changes you've had recently
• All medications, vitamins, herbs or other supplements you're taking, including dosages
• Questions to ask your doctor or mental health professional

Some basic questions to ask your doctor may include:

• Are my symptoms likely caused by SAD, or could they be due to something else?
• What else could be causing or worsening my symptoms of depression?
• What are the best treatment options?
• Would using a light box help my symptoms?
• Are there any restrictions that I need to follow or steps I should take to help improve my mood?
• Should I see a psychiatrist, psychologist or other mental health professional?
• Are medications likely to improve my symptoms?
• Is there a generic alternative to the medication you're prescribing me?
• Are there any brochures or other printed material that I can have? What websites do you recommend?

Don't hesitate to ask other questions during your appointment.

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Be ready to answer them to reserve time to go over any points you want to spend more time on. Your doctor may ask:

• What are your symptoms?
• When did you first begin having symptoms?
• Have your symptoms been continuous or occasional?
• How do your symptoms impact your daily activities?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?
• Do you have any other physical or mental health conditions?
• Are you taking any medications, supplements or herbal remedies?
• Do you use alcohol or recreational drugs?
• Do any of your blood relatives have SAD or another mental health condition?