The Winter Solstice on Dec. 21 signals the start of winter and the shortest day of the year, the day with the least amount of sunlight. For those with winter seasonal affective disorder, the winter solstice also signifies that each day going forward will have more sunlight and therefore relief for their malady, appropriately abbreviated as SAD.

Interestingly, although more common and mostly associated with the winter months and the loss of sunlight, SAD also can occur in summer months.

SAD simply refers to a change in mood related to the change of seasons. So for winter months with less sunlight, patients experience a depressive mood with the shortened days and the loss of sunlight.

The reverse works in the summer where patients can experience an elevated mood as a result of the change in the weather. To be diagnosed with SAD, patients need to exhibit a change in mood, either depression or mood elevation, for at least two years.

Signs and symptoms associated with winter SAD include a feel of low energy, listlessness, feeling depressed, problems sleeping, change in appetite or weight, difficulty concentrating or even thoughts of suicide.

Conversely, summer SAD symptoms and signs can include weight loss or agitation and/or anxiety but also can  include symptoms similar to winter’s, such as difficulty sleeping.

The causes for SAD are not conclusively known. Possible causes include a change in the biological clock caused by the reduced sunlight in winter or the increased sunlight in summer, changes in serotonin levels caused by reduced sunlight, and disruption in the body’s level of melatonin, which plays a role in sleep patterns and mood.

Risk factors for SAD include a family history of SAD and a history of major depressive episodes or history of bipolar disorder.

An interesting risk factor is that SAD is more common in those who live farther away from the equator. It is thought that those who live farther from the equator are at risk due to the greater changes in sunlight going through the season than those who live closer to the equator.

Complications of untreated SAD include depression, social withdrawal, substance abuse and even suicidal thoughts and behavior.

Treatment for SAD starts with a thorough medical examination to eliminate other causes of the patient’s complaints. This examination should include a physical examination and the appropriate laboratory tests. If no underlying reasons can be found to explain the patients’ complaints and SAD is diagnosed, then treatment can be started.

Treatment for SAD is based on medications, psychotherapy and light therapy. The first line of therapy is light or phototherapy in which the patient sits before a special light first thing in the morning. By doing this, it is believed that the light induces changes in brain chemicals and therefore the patient’s mood. It usually takes a few weeks for this treatment to work.

The second line of treatment is usually anti-depressants which are best started weeks before the onset of symptoms, since it takes time for the medications to begin to work.

Dr. Dwight S. Tyndall, FAAOS, is an outpatient spine surgeon practicing in the Region. His column, which appears every other week, covers a wide range of health and medical issues.