seasonal affective disorder

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Seasonal Affective Disorder



Seasonal affective disorder (SAD) is a form of depression most often associated with the lack of daylight in extreme northern and southern latitudes from the late fall to the early spring.


Although researchers are not certain what causes seasonal affective disorder, they suspect that it has something to do with the hormone melatonin. Melatonin is thought to play an active role in regulating the "internal body clock," which dictates when humans feel like going to bed at night and getting up in the morning. Although seasonal affective disorder is most common when light is low, it may occur in the spring, and it is then often called reverse SAD.

Causes and symptoms

The body produces more melatonin at night than during the day, and scientists believe it helps people feel sleepy at nighttime. There is also more melatonin in the body during winter, when the days are shorter. Some researchers believe that excessive melatonin release during winter in people with SAD may account for their feelings of drowsiness or depression. One variation on this idea is that, during winter, people's internal clocks may become out of sync with the light-dark cycle, leading to a long-term disruption in melatonin release.
Seasonal affective disorder, while not an official category of mental illness listed by the American Psychiatric Association, is estimated to affect 10 million Americans, most of whom are women. Another 25 million Americans may have a mild form of SAD, sometimes called the "winter blues" or "winter blahs." The risk of SAD increases the further from the equator a person lives.
The symptoms of SAD are similar to those of other forms of depression. People with SAD may feel sad, irritable, or tired, and may find themselves sleeping too much. They may also lose interest in normal or pleasurable activities (including sex), become withdrawn, crave carbohydrates, and gain weight.


Doctors usually diagnose seasonal affective disorder based on the patient's description of symptoms, including the time of year they occur.


The first-line treatment for seasonal affective disorder is light therapy, exposing the patient to bright artificial light to compensate for the gloominess of winter. Light therapy uses a device called a light box, which contains a set of fluorescent or incandescent lights in front of a reflector. Typically, the patient sits for 30 minutes next to a 10,000-lux box (which is about 50 times as bright as ordinary indoor light). Light therapy appears to be safe for most people. However, it may be harmful for those with eye diseases. The most common side effects are vision problems such as eye strain, headaches, irritability, and insomnia. In addition, hypomania (elevated or expansive mood, characterized by hyperactivity and inflated self esteem) may occasionally occur.
Recently, researchers have begun testing whether people who do not completely respond to light therapy can benefit from tiny doses of the hormone melatonin to reset the body's internal clock. Early results look promising, but the potential benefits must be confirmed in larger studies before this type of treatment becomes widely accepted.
Like other types of mood disorders, seasonal affective disorder may also respond to medication and psychotherapy. The four different classes of drugs used for mood disorders are:
  • heterocyclic antidepressants (HCAs), such as amitriptyline (Elavil)
  • selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (Prozac), paroxetine (Paxil), and sertraline (Zoloft)
  • monoamine oxidase inhibitors (MAO inhibitors), such as phenelzine sulfate (Nardil) and tranylcypromine sulfate (Parnate)
  • Lithium salts, such as lithium carbonate (Eskalith), often used in people with bipolar mood disorders, are often useful with SAD patients; many SAD patients also suffer from bipolar disorder (excessive mood swings; formerly known as manic depression)
A number of psychotherapy approaches are useful as well. Interpersonal psychotherapy helps patients recognize how their mood disorder and their interpersonal relationships interact. Cognitive-behavioral therapy explores how the patient's view of the world may be affecting mood and outlook.


Most patients with seasonal affective disorder respond to light therapy and/or antidepressant drugs.



American Psychiatric Association. 1400 K Street NW, Washington DC 20005. (888) 357-7924.
National Depressive and Manic Depressive Association (NDMDA). 730 N. Franklin St., Ste. 501, Chicago, IL 60610. (800) 826-3632.
National Institute of Mental Health. Mental Health Public Inquiries, 5600 Fishers Lane, Room 15C-05, Rockville, MD 20857. (888) 826-9438.

Key terms

Cognitive behavioral therapy — Psychotherapy aimed at helping people change their attitudes, perceptions, and patterns of thinking.
Melatonin — A naturally occurring hormone involved in regulating the body's "internal clock."
Serotonin — A chemical messenger in the brain thought to play a role in regulating mood.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

seasonal affective disorder

a mood disorder characterized by depression, extreme lethargy, increased need for sleep, overeating, and carbohydrate craving. It recurs each year in one or more specific seasons, most commonly the winter months, and is hypothesized to be related to melatonin levels.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

sea·son·al af·fec·tive dis·or·der (SAD),

a depressive mood disorder that occurs at approximately the same time year after year and spontaneously remits at the same time each year. The most common type is winter depression and it is characterized by morning hypersomnia, low energy, increased appetite, weight gain, and a craving for carbohydrates, all of which remit in the spring.
Farlex Partner Medical Dictionary © Farlex 2012

seasonal affective disorder

n. Abbr. SAD
A mood disorder in which abnormal moods occur in a regular seasonal pattern, such as depression during the short days of winter. It is sometimes classified as a specific subtype of major depressive disorder or bipolar disorder.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

seasonal affective disorder

A clinical form of depression with an onset in the late fall and remission in the spring; female:male ratio, 2:1.

Uncertain; reduced daily sunlight causes a drop in serotonin; PET scan data has linked depression to an increased in blood flow through the anterior limbic system, which may ultimately lead to hypoactivity; melatonin is decreased in women in summer and unchanged in men.
Some SAD patients respond to high-intensity light, which alters the circadian rhythm, a therapy that is most effective in the morning; a light intensity of 10,000 lux viewed at close range may reset the biological clock.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

seasonal affective disorder

SAD, winter 'blues,' winter depression Psychiatry A clinical form of depression with an onset in late fall and remission in spring. See Bright light therapy; Cf Melancholia, Melanocholy.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

sea·son·al af·fec·tive dis·or·der

(SAD) (sēzŏn-ăl a-fektiv dis-ōrdĕr)
A depressive mood disorder that occurs at approximately the same time year after year and spontaneously remits at the same time each year. The most common type is winter depression, characterized by morning hypersomnia, low energy, increased appetite, weight gain, and carbohydrate craving, all of which remit in the spring.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

sea·son·al af·fec·tive dis·or·der

(SAD) (sēzŏn-ăl a-fektiv dis-ōrdĕr)
Depressive mood disorder that occurs at approximately the same time each year and spontaneously remits at the same time each year. Most common type is winter depression characterized by morning hypersomnia, low energy, increased appetite, weight gain, and a craving for carbohydrates, all of which findings remit in the spring.
Medical Dictionary for the Dental Professions © Farlex 2012
References in periodicals archive ?
Some signs and symptoms of seasonal affective disorder may just feel like normal parts of going through a rough patch during the winter.
The Can-SAD Study: A randomized Controlled Trial of the Effectiveness of Light Therapy and Fluoxetine in patients with winter Seasonal Affective Disorder. Am J Psychiatry 2006; 163: 805-12.
* Difficulty concentrating and processing information Spring and summer seasonal affective disorder (summer depression)
Proposed mechanisms for seasonal affective disorder
Light therapy, antidepressants, cognitive-behavioral therapy (CBT), or some combination of those treatments can offer relief to patients with seasonal affective disorder (SAD).
* The National Organization for Seasonal Affective Disorder (NOSAD)
Dancers in the northern hemisphere who develop seasonal affective disorder (SAD) during the late fall and winter months may crave sweet and starchy foods and gain weight.
It is most often used by shift workers, jet-lagged travelers and those with Seasonal Affective Disorder to help re-set biological clocks.
Seasonal Affective Disorder (SAD) emerges in those who don't receive enough sunlight, a bout of the flu can put a damper on anyone's spirits, and even the holidays make many people feel depressed or lonely.
Seasonal Affective Disorder, or SAD as it is also called, is a disorder that affects people in the part of the world where there is little light in the winter.
Fifteen years ago, researchers identified a condition called seasonal affective disorder (SAD).