Seasonal Affective Disorder is Underdiagnosed
Depression Occurring at Specific Times of the Year Is Often Missed
Sep 21, 2009
The Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) describes seasonal affective disorder (SAD) as a “specifier” for major depressive disorder: People who suffer from SAD experience episodes of major depression – or bipolar episodes – at certain times of the year. (American Psychiatric Association. Task Force on DSM-IV. Diagnostic and Statistical Manual of Mental Disorders. 4th ed. Washington, D.C.: American Psychiatric Association, 1994)
Strangely, standardized screening questionnaires used by physicians to help diagnose SAD are not sensitive for identifying individuals with the disorder. Because an accurate diagnosis is much more likely to be made through detailed interviews with patients, and because many medical providers don’t have time for such interviews, SAD is underdiagnosed in most doctors’ offices. (Higgins E. A review of unrecognized mental illness in primary care. Prevalence, natural history, and efforts to change the course. Arch Fam Med 1994;3:908-17)
Because many people with SAD are not diagnosed, the true prevalence of the disorder is unknown. More people in northern latitudes may suffer from the disease, and the prevalence may vary among different ethnic groups at the same latitude. (Magnusson A. An overview of epidemiological studies on seasonal affective disorder. Acta Psychiatr Scand 2000;101:176-84 and Mersch P, et al. Seasonal affective disorder and latitude: a review of the literature. J Affect Disord 1999;53:35-48)
Diagnostic Criteria for Seasonal Affective Disorder (SAD)
According to DSM-IV, seasonal affective disorder can be diagnosed if:
- There has been a regular temporal relationship between the onset of major depressive episodes in bipolar I or bipolar II disorder or major depressive disorder, recurrent, and a particular time of the year (e.g., regular appearance of the major depressive episode in the fall or winter). (NOTE: Do not include cases in which there is an obvious effect of seasonal-related psychosocial stressors [e.g., regularly being unemployed every winter])
- Full remissions (or change from depression to mania or hypomania) also occur at a characteristic time of the year (e.g., depression disappears in the spring)
- In the past two years, two major depressive episodes have occurred that demonstrate the temporal seasonal relationships, and no nonseasonal major depressive episodes have occurred during that same period
- Seasonal major depressive episodes (as described above) substantially outnumber the nonseasonal major depressive episodes that may have occurred over the individual's lifetime
In other words, people with SAD have a regular occurrence of significant depression that only occurs at specific times of the year, no other reasons (such as seasonal unemployment) exist to explain their mood change, they experience improvement between bouts of depression, their episodes of depression have occurred for at least two years, and it is unusual for major depression to occur at other times of the year.
Conditions that Occur with Seasonal Affective Disorder
SAD is associated with abnormalities in the levels of serotonin and other neurotransmitters in the central nervous system. Therefore, conditions that share common neurotransmitter pathways often occur in conjunction with SAD; some are hereditary:
- Generalized anxiety disorder
- PMS
- Panic disorder
- Bulimia
- Attention-deficit/hyperactivity disorder (ADHD)
- Chronic fatigue syndrome
- Alcohol abuse (often coincides with seasonal SAD symptoms)
(Adapted from Lurie S, et al. Seasonal affective disorder. Am Fam Phys. 2006;74[9]:1521-24)
Light Therapy for Seasonal Affective Disorder (SAD)
SAD’s seasonality is influenced by shifts in circadian rhythms, which in turn are affected by available daylight reaching the pineal gland in the brain.
Light replacement therapy for SAD has been extensively studied, and its benefits are well documented. In fact, light therapy appears to be at least as effective as pharmacological therapy for treating SAD.
The optimal dose of light must be supplied by units that are specifically designed to treat seasonal affective disorder. This ensures appropriate brightness and sufficient filtration of ultraviolet light.
The light dosage found to be effective in the majority of studies is 5,000 lux daily, administered either at 2,500 lux over two hours or 10,000 lux for 30 minutes. Early morning light therapy is recommended, as this more effectively regulates the circadian secretion of melatonin and serotonin.
Like drug treatment, light therapy can precipitate manic episodes in some individuals. (Sohn C, Lam R. Treatment of seasonal affective disorder: unipolar versus bipolar differences. Curr Psychiatry Rep 2004;6:478-85)
Drug Treatment for Seasonal Affective Disorder (SAD)
Most studies that evaluate the treatment of SAD with medications don’t offer adequate comparisons with light therapy. It is therefore difficult to determine if one therapy is better than the other.
Selective serotonin reuptake inhibitors (SSRIs) – fluoxetine (Prozac), sertraline (Zoloft), and citalopram (Celexa) – are the most studied and have reduced the symptoms of SAD in clinical studies.
Light therapy, medications, and behavioral therapies can be combined for particularly difficult cases.
Seasonal affective disorder, a “subset” of major depressive disorder, can be disabling if undiagnosed and untreated. Fortunately, most sufferers respond to light therapy, medications, or a combination of treatments.
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