Many people go through short periods when they feel sad or unlike their usual selves. Sometimes, these mood changes begin and end when the seasons change. Many people feel “down” or have the “winter blues” when the days get shorter in the fall and winter and feel better in the spring when longer daylight hours return.
Sometimes, these mood changes are more serious and can affect how a person feels, thinks, and behaves. If you have noticed significant changes in your mood and behavior when the seasons change, you may be experiencing seasonal affective disorder (SAD).
In most cases, SAD symptoms start in the late fall or early winter and go away during the spring and summer, known as winter-pattern SAD or winter depression. Other people experience depressive symptoms during the spring and summer months, known as summer-pattern SAD or summer depression. Summer-pattern SAD is less common.
What are the signs and symptoms of SAD?
SAD is a type of depression characterized by a recurrent seasonal pattern, with symptoms lasting about 4−5 months out of the year. The signs and symptoms of SAD include those associated with depression as well as disorder-specific symptoms that differ for winter-pattern versus summer-pattern SAD.
Not every person with SAD experiences all the symptoms listed below. Learn about signs and symptoms of depression.
Symptoms of depression can include:
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- Persistent sad, anxious, or “empty” mood most of the day, nearly every day, for at least 2 weeks
- Feelings of hopelessness or pessimism
- Feelings of irritability, frustration, or restlessness
- Feelings of guilt, worthlessness, or helplessness
- Loss of interest or pleasure in hobbies and activities
- Decreased energy, fatigue, or feeling slowed down
- Difficulty concentrating, remembering, or making decisions
- Changes in sleep or appetite or unplanned weight changes
- Physical aches or pains, headaches, cramps, or digestive problems that do not have a clear physical cause and do not go away with treatment
- Thoughts of death or suicide or suicide attempts
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For winter-pattern SAD, additional symptoms can include:
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- Oversleeping (hypersomnia)
- Overeating, particularly with a craving for carbohydrates, leading to weight gain
- Social withdrawal (feeling like “hibernating”)
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What causes SAD?
Researchers are still determining what causes SAD. Most research to date has investigated potential causes of winter-pattern SAD because it is more common and easier to study. As a result, less is known about summer-pattern SAD, and more research is needed.
Studies indicate that people with SAD, especially winter-pattern SAD, have reduced levels of the brain chemical serotonin, which helps regulate mood. Research also suggests that sunlight affects levels of molecules that help maintain normal serotonin levels. Shorter daylight hours may prevent these molecules from functioning properly, contributing to decreased serotonin levels in the winter.
Vitamin D deficiency may exacerbate these problems in people with winter-pattern SAD because vitamin D is believed to promote serotonin activity. In addition to vitamin D consumed in food, the body produces vitamin D when exposed to sunlight on the skin. With less daylight in the winter, people with SAD may have lower vitamin D levels, further reducing serotonin activity.
Other studies suggest that both forms of SAD relate to altered levels of melatonin—a hormone important for maintaining the normal sleep−wake cycle. People with winter-pattern SAD produce too much melatonin, which can increase sleepiness and lead to oversleeping.
In contrast, people with summer-pattern SAD may have reduced melatonin levels, consistent with long, hot days worsening sleep quality and leading to depression symptoms. Longer daylight hours, shorter nights, and high temperatures can also cause sleep disruptions. However, these theories have not been systematically tested.
Both serotonin and melatonin help maintain the body’s daily rhythm tied to the seasonal night−day cycle. In people with SAD, changes in serotonin and melatonin disrupt normal daily rhythms. As a result, they can no longer adjust to seasonal changes in day length, leading to sleep, mood, and behavior changes.
Negative thoughts and feelings about the winter or summer and its associated limitations and stresses are also common among people with SAD (as well as others). It is unclear, however, whether these thoughts are causes or effects of the mood disorder, but they can be a useful focus of treatment.
Treatments are available to help people with SAD. They fall into four main categories that can be used alone or in combination:
- Light therapy
- Psychotherapy
- Antidepressant medication
- Vitamin D
Light therapy and vitamin D are treatments for winter-pattern SAD, whereas psychotherapy and antidepressants are used to treat depression in general, including winter- and summer-pattern SAD. There are no treatments specific to summer-pattern SAD.
Talk to a health care provider about the potential benefits and risks of different treatment options and which treatment is best for you.
Source: https://www.nimh.nih.gov/health/publications/seasonal-affective-disorder