Seasonal Affective Disorder: Causes, Symptoms and Risk Factors

Seasonal Affective Disorder (SAD) is a form of depression that occurs at the same time each year, generally associated with the changing seasons. The most common type of SAD is winter seasonal affective disorder, which generally begins during autumn and lasts until spring. A less common type of SAD, known as summer seasonal affective disorder, often begins in late spring and lasts until autumn. The symptoms of seasonal affective disorder can be mild ("winter blues") or severe (deep depression with suicidal thoughts) and alternate with normal moods during the rest of the year.

Seasonal Affective Disorder: What Causes It?
While the exact cause of seasonal affective disorder is unknown, it is felt the brain chemicals melatonin and serotonin play key roles in the disorder. Melatonin helps control the sleep cycle. The body increases production of melatonin when it is dark outside. Serotonin plays a part in controlling emotions. Production of serotonin is increased when a person is exposed to sunlight.

The seasonal shifts in the hours of light and darkness can lead to imbalances in melatonin and serotonin levels. The long hours of darkness during winter may lead to low levels of serotonin and high levels of melatonin. Conversely, the long daylight hours of summer may cause the body to have too much serotonin and not enough melatonin. This explains why seasonal affective disorder becomes more common the farther people move away from the equator.

Seasonal Affective Disorder: What Are the Symptoms?
The symptoms of winter seasonal affective disorder include:
Mood changes
Depression
Hopelessness
Anxiety
Loss of energy
Daytime fatigue
Withdrawal from society
Excessive sleeping or oversleeping on a regular basis
Loss of interest in previously enjoyed hobbies and activities
Cravings for foods high in carbohydrates or sugar
Weight gain
Difficulty concentrating
Decreased sex drive

Symptoms generally begin in October, though some people may begin to notice the beginning stages as early as August. Symptoms begin to subside in March or April, with normality occurring by early May.

The symptoms of summer seasonal affective disorder include:
Anxiety
Insomnia
Irritability
Agitation
Weight loss
Lack of appetite
Increased sex drive

Symptoms generally begin in late spring and last into autumn, with normality occurring by winter.

In very rare cases, both forms of seasonal affective disorder are experienced with symptoms subsiding in the spring and fall. These people feel their best around the equinoxes.

Seasonal Affective Disorder: Who Gets It?
While children and teens may develop seasonal affective disorder, it is more common in adults over the age of 20. Women are four times more likely to have seasonal affective disorder than men, but men often experience more severe symptoms. The chance of seasonal affective disorder is increased if a family member has the disorder or another psychiatric condition. Studies show having a close relative with a severe depressive disorder increases a person's risk for seasonal affective disorder by 55 percent, while alcoholism in the family increases the risk by 34 percent.

People who work in buildings with few to no windows or are on the night shift may experience symptoms similar to seasonal affective disorder throughout the year due to a lack of adequate exposure to sunlight.

Sources:
National Alliance on Mental Illness:
Seasonal Affective Disorder

KidsHealth.org
Teen Health - What Causes SAD?
What Are the Symptoms of SAD?
Who Gets SAD?

Northern County Psychiatric Associates:
Seasonal Affective Disorder: Winter Depression

Mayo Clinic:
Seasonal affective disorder (SAD) - Symptoms
Seasonal affective disorder (SAD) - Causes
Seasonal affective disorder (SAD) - Risk Factors

FamilyDoctor.org:
Seasonal Affective Disorder