What is seasonal affective disorder?

Causes and Symptoms

In order for a person to be diagnosed with seasonal affective disorder, the criteria for a major depressive episode as defined in the Diagnostic and Statistical Manual of Mental Disorders: DSM-5 (5th ed., 2013) must be met. These criteria include having a depressed mood for most of the day, nearly every day, for a two-week period. Signs of a depressed mood can include reports of feeling sad, empty, or tearful. In addition, loss of interest or pleasure in almost all activities for most of the day, nearly every day, for at least two weeks can be part of a major depressive episode. If either of these two criteria is identified, then the patient must show four or more of the following symptoms: significant weight loss when not dieting or weight gain of more then 5 percent of body weight within a month, insomnia or hypersomnia nearly every day, psychomotor agitation or psychomotor retardation nearly every day, fatigue or loss of energy nearly every day, feelings of worthlessness or inappropriate guilt, diminished ability to think or concentrate, and recurrent thoughts of death or suicide ideation. If the patient has experienced two recurrent major depressive episodes in the last two years that demonstrate temporal relationship to season, then a diagnosis of seasonal affective disorder can be made.

In addition to the DSM-5 criteria for a major depressive episode, a person with seasonal affective disorder may experience a number of other symptoms. Anxiety is a common symptom of depression and affects as many as 90 percent of all persons with depression. The depressed person often loses interest in sexual activities, and female patients may experience abnormal menstruation. About two-thirds of all depressed patients contemplate suicide, and approximately 15 percent complete suicide. It should be noted that some depressed persons do not complain of mood disturbance even as they are withdrawing from family, friends, and activities. The majority of depressed persons complain about reduced energy and difficulty finishing tasks. Thus, they become impaired at school or work and lack the motivation to begin new projects.

Seasonal patterns of depression can also be identified among patients who have bipolar disorder. In this disorder, the patient experiences both major depressive episodes and elated moods. When a patient shows an elevated, expansive, or irritable mood that is excessive and impairs daily functioning, then a manic episode can be diagnosed. The elevated mood is euphoric and leads the person to engage in excessive behaviors that demonstrate poor judgment. These patients have an unlimited amount of energy and continue their activities without the need for sleep or rest. If a person experiences both manic episodes and recurrent major depressive episodes during certain seasons of the year, then the patient has a bipolar disorder with a seasonal pattern.

The causes of seasonal affective disorder are not well understood, but they probably involve dysfunction in a number of hormones and neurotransmitters—such as low levels of seratonin, a neurotransmitter associated with well-being—genetic influences, and personality, affected by reduced sunlight. The seasonal mood changes have led to particular interest in studying the circadian rhythms of these individuals. Many studies have found that the circadian rhythms of persons with seasonal affective disorder are phase-delayed relative to the sleep-wake cycle. Seasonal affective disorder is considered an abnormal response to seasonal changes in length of the day and appears related to the photoperiod between sunrise and sunset. The hormone melatonin, which helps to regulate sleep-wake cycles, has been implicated. Melatonin is secreted by the pineal gland in response to darkness and is suppressed by bright light that enters through the retinal-central nervous system pathway. Genetic studies have shown that between 35 and 69 percent of persons with seasonal affective disorder have a family history of depression, and 7 to 37 percent have a family member who had seasonal depression.

Seasonal affective disorder is diagnosed following a clinical interview with the patient in order to identify the DSM-5 criteria. The patient provides self-reports of possible symptoms, and the interviewer observes the person for any signs of depression that could fulfill the diagnostic requirements. In addition, seasonal affective disorder may not occur in isolation. Individuals may also suffer from other mental health problems, such as substance use disorders. Therefore, in addition to diagnosing seasonal affective disorder, the diagnostic process should also focus on ruling out other conditions that may demand additional or specialized treatment.

Treatment and Therapy

Phototherapy or light therapy
involves exposing the patient to a bright light. The individual sits in front of a specific type of therapeutic light source for approximately thirty minutes to ninety minutes, usually in the morning each day. Light visors with a light source built into the brim also may be used for treatment. Antidepressant medication is often used in conjunction with phototherapy. Serotoninergic antidepressants are most often used to augment light therapy.

Perspective and Prospects

Prevalence rates point to the fact that winter seasonal affective disorder is more common than any other seasonal pattern. Evidence exists that people living in northern climates have a higher incidence of the disorder than do those living at other latitudes. Individuals with seasonal affective disorder typically experience depression as the amount of daylight decreases with advancing winter. Women have been found to represent at least 75 percent of patients with seasonal depression, being two to four times as likely than men to develop this problem. Most individuals who will develop this problem do so in their twenties and thirties. The rates of newly diagnosed seasonal affective disorder tend to decrease during the fifties and markedly decrease after age sixty-five. Understanding these age-related trends is likely to be a focus of future research that may perhaps uncover new understandings of the etiology of and treatment for the disorder.

Light therapy, the dominant treatment for this disorder, can be challenging for some because individuals must build time into their schedules to be exposed to the light. Future treatments in this area are likely to seek ways of better integrating exposure to light into the environment and activities of those affected. Light visors were a step in this direction, and other convenient methods can be expected.

Bibliography

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Partonen, Timo, and Andres Magnusson, eds. Seasonal Affective Disorder: Practice and Research. 2d ed. New York: Oxford University Press, 2010.

Riley, Julie Smith, and Brian Randall. "Seasonal Affective Disorder." Health Library, Mar. 6, 2013.

Rohan, Kelly. "Seasonal Affective Disorder Sufferers Have More than Just Winter Blues." American Psychological Association, Feb. 4, 2013.

Rosenthal, Norman E. Winter Blues: Everything You Need to Know to Beat Seasonal Affective Disorder. 4th ed. New York: Guilford Press, 2012.

"Seasonal Affective Disorder." MedlinePlus, Mar. 13, 2013.

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