Seasonal affective disorder (SAD)

Seasonal affective disorder (SAD) is a type of depression that's related to changes in seasons — seasonal affective disorder (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. These symptoms often resolve during the spring and summer months. Less often, SAD causes depression in the spring or early summer and resolves during the fall or winter months.

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

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 listless, sad or down most of the day, nearly every day
• Losing interest in activities you once enjoyed
• Having low energy and feeling sluggish
• Having problems with sleeping too much
• Experiencing carbohydrate cravings, overeating and weight gain
• Having difficulty concentrating
• Feeling hopeless, worthless or guilty
• Having thoughts of not wanting to live

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
• Increased irritability

Seasonal changes and bipolar disorder

People who have bipolar disorder are at increased risk of seasonal affective disorder. In some people with bipolar disorder, episodes of mania may be linked to a specific season. For example, spring and summer can bring on symptoms of mania or a less intense form of mania (hypomania), anxiety, agitation and irritability. They may also experience depression during the fall and winter months.

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 health care provider. 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.
• Low level of vitamin D. Some vitamin D is produced in the skin when it's exposed to sunlight. Vitamin D can help to boost serotonin activity. Less sunlight and not getting enough vitamin D from foods and other sources may result in low levels of vitamin D in the body.

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

There's no known way to prevent the development of seasonal affective disorder. However, if you take steps early on to manage symptoms, you may be able to prevent them from getting worse over time. You may be able to head off serious changes in mood, appetite and energy levels, as you can predict the time of the year in which these symptoms may start. Treatment can help prevent complications, especially if SAD is diagnosed and treated before symptoms get bad.

Some people find it helpful to begin treatment before symptoms would normally start in the fall or winter, and then continue treatment past the time symptoms would normally go away. Other people need continuous treatment to prevent symptoms from returning.