Drug Criteria & Outcomes: Do changes in the seasons make some people SAD?

By Andrea Williams, PharmD candidate
Harrison School of Pharmacy
Auburn (AL) University

Many people experience the "winter-time blues." Some people may feel down, have less energy, put on a few pounds, or have difficulty getting out of bed in the mornings during the dark, short days of winter. However, people who have seasonal affective disorder (SAD) experience these same symptoms to the degree that it inhibits their normal daily life. SAD sufferers often feel chronically depressed and fatigued. They also do not want to be socially active and may withdraw from the world. In the United States, about 6% of the population (approximately 10 million people) suffers from SAD. This disorder is predominately found in females and in people 20-30 years of age.

Norman E. Rosenthal, MD, and his research group at the National Institutes of Mental Health first described seasonal affective disorder in 1984. They coined the term SAD to describe a type of depression that varies with the seasons. SAD is characterized by four aspects: recurrent major depressive episodes that start (September-October) and end (March-April) at the same time each year; full remission of symptoms during the unaffected period of the year (May-August); relatively more seasonal depressive episodes than non-seasonal episodes; and depressive episodes occurring for at least two consecutive years. These criteria are used in the fourth edition of the standard psychiatric Diagnostic and Statistical Manual for diagnostic purposes. Also, several instruments are used in the diagnosis of SAD, such as the Seasonal Pattern Assessment Questionnaire, which is a self-report questionnaire that retrospectively assesses the magnitude of seasonal change in sleep, social activity, mood, weight, appetite, and energy. Another instrument that measures the severity of SAD is the Structured Clinical Interview Guide for the Hamilton Depression Rating Scale, SAD version.

The usual symptoms of SAD are depression including low mood, reduced interest, decreased concentration, low energy, and fatigue. SAD sufferers also experience "reverse" or "atypical" vegetative symptoms of depression such as increased sleep, increased appetite, unacceptable weight gain, and carbohydrate/sweets craving.

The etiology and pathophysiology of SAD are unknown. There are three main hypotheses for SAD: the circadian rhythm disturbance, melatonin, and neurotransmitters. The circadian rhythm disturbance hypothesizes that biological rhythms are cyclical variations in biological activities and functions (e.g., physiological function and emotional state). Therefore, an abnormal change in the biological function causes affective illness, which is a disruption of the patient’s sleeping patterns, diurnal variation in mood, and seasonal patterns of recurrence. It is thought that the circadian rhythm is linked to the light-dark cycle of the solar day, so that if an individual is unable to adapt to changes, then it may affect his or her well-being.

Another hypothesis involves melatonin, an endogenous hormone that is secreted nocturnally by the pineal gland and is believed to cause symptoms of depression. Melatonin is produced at increased levels in the dark, so when the days are shorter and darker, the production of this hormone increases; however, melatonin production can be suppressed by bright light.

The third hypothesis involves neurotransmitters such as serotonin. Serotonin is thought to be linked to SAD because it has a distinct seasonal pattern of metabolism in normal humans. The lowest levels of serotonin generally occur in the winter and spring, whereas the highest levels occur in the summer and fall. These three hypotheses have been studied, but none have been proven to explain completely the manifestations of SAD.

There are two main treatments for this disorder: phototherapy and antidepressant drug therapy. There have been more than 60 controlled trials of light therapy in SAD, with most demonstrating effective results. Light therapy involves sitting in front of a light box during the fall and winter months, usually for 30 minutes a day. The usual "dose" of light is 10,000 lux (illuminance). Response to light therapy usually is seen within two to four days; however, some patients may need light exposure for up to two weeks before seeing an improvement. Even though the side effects of light therapy are rare, the most common side effects reported in the clinical trials are listed in Table 1.

In clinical trials, the most effective time to receive light therapy is in the early morning, upon awakening. However, some patients may benefit from light therapy at other times during the day. There are no absolute contraindications to light therapy and no evidence that light therapy is associated with ocular or retinal damage.

Antidepressant drug therapy is another treatment for SAD, although there are only two reliable clinical trials supporting this use. The first trial found that sertraline was significantly superior to placebo in regard to clinical response rate and depression scores. The other study found that fluoxetine was significantly superior to placebo in the clinical response rates but not in the depression scores. The usual doses of the antidepressants are the same as those used in other nonseasonal major depressive disorders. Sertraline and fluoxetine are generally well-tolerated. Patients using antidepressant drugs generally demonstrate an improvement in symptoms within three to four weeks. Other antidepressants may be effective in the treatment of SAD but have not been studied.

Most patients are treated only during the symptomatic winter months, and then discontinue their treatments during the spring and summer months. The treatments are then restarted in the autumn. Some patients can wait until they have mild symptoms before restarting treatment; others may opt to start treatment well ahead of their usual onset time (at least two weeks ahead for light therapy and four weeks ahead for antidepressants) to prevent an episode. Because the onset of action of light is rapid, continuous light therapy throughout the summer is not necessary, although some patients occasionally use light therapy for transient, mild symptoms during the summer. Continuous antidepressant treatment (throughout the summer) is indicated in patients who have problems with compliance, take a long time to taper on and off medications, have difficulty dating onset of symptoms in the fall, or have occasional, transient symptoms in the summer.

How do you choose between light therapy and antidepressant drug therapy? Listed in Table 2, are important factors for patients and physicians to consider when choosing a therapy.


• American Family Physician. Seasonal affective disorder [cited March 2000]. Available at: www.findarticles.com/cf_0/m3225/5_61/61432742/print.jhtml. Accessed Jan. 15, 2002.

• Canadian consensus guidelines for the treatment of seasonal affective disorder: A summary of the report of the Canadian consensus group on SAD [cited 1999]. Available at: www.fhs.mcmaster.ca. Accessed Jan. 15, 2002.

• National Mental Health Association. Depression: Seasonal affective disorder [cited 2001]. Available at: www.nmha.org/infoctr/factsheets/27.cfm. Accessed Jan. 15, 2002.

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• Weir E. Winter needn’t be the SAD season. Can Med Assoc J 2001;164:256.