Seasonal Affective Disorder and Light Therapy

What is seasonal affective disorder?
Seasonal affective disorder is a major (serious) form of depression that occurs at the same time each year. Researchers have identified two types of SAD. The most common type, known as "winter depression," usually begins in the late fall to early winter months and ends in spring. Seasonal affective disorder can also occur in the summer (known as "summer depression").

Surveys estimate that 4 to 6 percent of the general population experience SAD. Women with SAD outnumber men four to one. The disorder usually begins in person's early twenties and the risk for developing SAD decreases with age (Saeed and Bruce).

What are the symptoms of seasonal affective disorder?
People who suffer from SAD can have the common symptoms of depression such as sadness, anxiety, lost of interest in usual activities, withdrawal from social activities, and an inability to concentrate. Symptoms most common to winter depression include:

How is seasonal affective disorder diagnosed?
Physicians can diagnose SAD based on criteria (a set of standards) developed by the American Psychiatric Association. Your physician can determine if you are suffering from depression and if this depression is a seasonal affective disorder. Tables 1 and 2 below list the criteria used for diagnosing a depressive episode and SAD.

What causes SAD?
The exact cause of SAD is unknown, but researchers suspect changes in the availability of sunlight plays an important role. Statistics show that winter depression becomes increasingly more common the farther people live north or south of the equator. Episodes of winter depression also tend to be longer and more severe at higher latitudes (Saeed and Bruce).

How is seasonal affective disorder different from the "holiday blues?"
Many people use the expression "holiday blues" to refer to a sadness or depression occurring during winter or the holiday season. This term should be differentiated from SAD. The holiday blues are related to psychosocial factors such as increased family obligations, isolation, decreased exercise, expectations that one "should" feel good, or association of the holidays with early memories and possible unresolved childhood conflicts.

In contrast, SAD is a subtype of a major depressive disorder (or bipolar disorder) with seasonal patterns and appears to be more biological in origin. (Rosenthal).

How is winter depression treated?
Research now shows that light therapy, or exposure to light, is an effective treatment for winter depression. Light therapy is administered by a 10,000-lux light box, which contains white fluorescent light tubes covered with a plastic screen that blocks ultraviolet rays. Full-spectrum light is not necessary (Saeed and Bruce).

The patient sits in front of the box with his or her eyes open, but should not look directly into the light. The therapy begins with daily sessions of 10 to 15 minutes, which are gradually increased to 30 to 45 minute sessions. Ninety minutes of exposure per day is often prescribed. The therapy typically continues until spring.

When should light therapy by prescribed?

Circumstances supporting the first-line use of light therapy5

How soon does light therapy work?
Most people notice improvement in 2 to 4 days. In some cases, symptoms may not improve for several weeks. If symptoms are worsening or do not improve after 4 to 6 weeks of therapy, see your physician. You may require a change in treatment.

Does light therapy cause side effects?
Light therapy can cause these side effects (Saeed and Bruce).

What other forms of treatment are available?
Treatments that may be helpful for SAD but require further testing include:

Resources for patients with seasonal affective disorder

Light Fixtures Sources

Apollo Light Systems
352 West 1060 South
Orem, Utah, 84058
1 (800) 545-9667

Hughes Lighting Technologies
34 Yacht Club Drive
Lake Hopatcong, NJ 07849
(973) 663-1214

Northern Light Technologies
8971 Henri Bourassa West
Montreal, Canada H45 1P7
1 (800) 263-0066

The SunBox Company
19217 Orbit Drive
Gaithersburg, MD 20879
1 (800) 548-3968

Information Sources

National Organization for Seasonal Affective Disorders (NOSAD)
P.O. Box 40190
Washington, DC 20016

National Depressive and Manic Depressive Association (NDMDA)
730 N. Franklin, Suite 501
Chicago, IL 60610
1 (800) 82-NDMDA (800-826-3632)

Society for Light Treatment and Biological Rhythms
10200 W. 44th Ave, #304
Wheat Ridge, CO 80033-2840
(303) 424-3697

National Institute of Mental Health (NIMH)
1 (800) 421-4211

National Mental Health Association (NMHA)
1021 Prince St.
Alexandria, VA 22314-2971
1 (800) 969-6642

Rosenthal, NE. Diagnosis and treatment of seasonal affective disorder. JAMA (serial online). 1993; 270(22): 2717-2720. Available at: http// Accessed November 6, 1998.

Saeed, SA, Bruce, TJ. Seasonal affective disorders. American Family Physician. 1998, 57:1340-1346

American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 4th ed. 1994:327, 390.

Agency for Health Care Policy and Research Clinical Practice Guidelines. Depression in primary care. Rockville, MD. 1993

Table 1
Diagnostic criteria for a major depressive episode3

A. At least five of the following symptoms have been present during the same two-week period, nearly every day, and represent a change from previous functioning. At least one of the symptoms is either (1) depressed mood or (2) loss of interest in pleasures.

Note: Do not include symptoms that are clearly due to a general medical condition, or mood-incongruent delusions or hallucinations

(1) Depressed mood (or alternatively can be irritable mood in children and adolescents).
(2) Markedly diminished interest in pleasure in all, or almost all, activities.
(3) Significant weight loss when not dieting or weight gain or decrease or increase in appetite
(4) Insomnia or hypersomnia
(5) Psychomotor agitation or retardation
(6) Fatigue or loss of energy
(7) Feelings of worthlessness or excessive or inappropriate guilt
(8) Diminished ability to think or concentrate, or indecisiveness
(9) Recurrent thoughts of death (not just fear of dying), recurrent suicidal ideation without a specific plan, or a suicide attempt or a specific plan for committing suicide.

B. The symptoms are not better accounted for by a mood disorder due to a general medical condition, a substance-induced mood disorder, or bereavement (normal reaction to the death of a loved one).

C. The symptoms are not better accounted for by a psychotic disorder like schizoaffective disorders.

(American Psychiatric Association)


Table 2
Criteria for seasonal pattern specifier

A. Regular temporal relationship between the onset of major depressive episodes and a particular time of the year (unrelated to obvious season-related psychosocial stressors).

B. Full remissions (or a change from depression to mania or hypomania) also occur at a characteristic time of the year.

C. Two major depressive episodes meeting Criteria A and B in the last two years and no nonseasonal episodes in the same period.

D. Seasonal major depressive episodes substantially outnumber the nonseasonal episodes over the individual's lifetime.

(American Psychiatric Association)

Selected case
A 39-year-old novelist presented in October complaining of increasing fatigue and severe "writer's block." For a month she had found it increasingly hard to wake up and get going in the morning. Her energy level was low; she was unable to concentrate on her writing and had trouble meeting deadlines. She had gained 2.25 kg and had difficulty avoiding desserts and high-calorie snacks. Whenever possible, she would nap at her desk or "vegetate" in front of the television. Bills went unpaid, and laundry piled up. She felt "disgusted" at her "incompetence" and pessimistic about the future.

A review of her history revealed that from her college years she had had similar difficulties, beginning in fall and winter and lasting until spring. For the last few winters, these episodes had been getting worse. During the spring, she would feel "alive again"--unusually energetic and euphoric, highly productive, and needed little sleep.

During the winter, the patient had been repeatedly tested for various physical ailments such as infections, mononucleosis, hypothyroidism, and hypoglycemia, all with negative results. On one occasion, she was diagnosed as suffering from depression and was treated with amitriptyline, but she couldn't tolerate the resulting drowsiness and dry mouth and discontinued the medication after a week. For much of her life, her mother had also suffered from recurrent depressions that occurred predominantly in the winter. One maternal uncle was an alcoholic. The patient had no history of any ophthalmologic difficulties, and physical examination and results of routine blood test were all normal (Rosenthal).

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