Seasonal Affective Disorder: Lighting the Way

Seasonal Affective Disorder: Lighting the Way

Pamela Johnson

"Whoever wishes to pursue the science of medicine in a direct manner must first investigate the seasons of the year and what occurs in them." Hippocrates (6)

Introduction

As the shortest day of the year approaches, more and more multi-colored lights and bright, festive decorations are splashed across houses and yards everywhere. Long ago, in more earthy times, people celebrated the solstice because it was the rebirth of the sun, when days began to lengthen and light began to return. As our ancient ancestors probably realized, their celebrations helped to keep spirits up when times were dark and cold, just as our modern holiday light displays function as a way to ward off the winter blues. (1)

However, not everybody can shake the sadness that comes at this time of year, usually because they are suffering from a type of clinical depression called Seasonal Affective Disorder (SAD). When a person has SAD, he or she regularly experiences depression in the winter months that then subsides in the spring and summer months. Although first identified around 1845, this mood disorder was not officially classified until 1984 when psychiatrist Norman E. Rosenthal, M.D., began to study cases of depression that seemed to occur during the winter only. (2) After an article was published in The Washington Post about his research, Rosenthal received a nationwide response from thousands of people who experienced the same symptoms he had observed in his patients. (3). After further research he compiled his studies in Winter Blues: Seasonal Affective Disorder: What It Is and How to Overcome It, which he recently revised, updated, and rereleased in October 1998.

Causes

Although the cause of this disorder is attributed to the lack of exposure to sunlight, it has not yet been determined whether a person's susceptibility to it is genetic or stress-related or both. Dr. Rosenthal finds the causes of SAD to be "a combination of factors including shortened daylight, stress and genetic vulnerability." (4). By means of his research, he calculated that some kind of depression is experienced by at least 14 percent of the population due to the decrease of exposure to sunlight in the winter. Many scientists feel SAD is "a product of modern society that confines us indoors," with stress levels easily increased by a work environment in which one hardly ever sees the sun. (4). Also, when working in an out-of-phase job, such as a night shift or a job that requires frequent traveling, people can undergo many health problems because their body rhythms are constantly thrown off by the lack of sunlight associated with their professions.

The sun's movement throughout the year causes natural biochemical changes in our circadian rhythms. These solar shifts even affect the activities of animals (for example, in the winter, hibernation). As though suffering from any of the following were not hard enough, lack of sunlight can cause those with PMS, alcoholism, bulimia nervosa, panic disorder, sleep disorders, and Bi-Polar disorder to suffer greater levels of stress and increased incidence of symptoms. (5). Also, because younger persons and women have more sensitive internal clocks to sunlight, they have a higher risk of getting SAD. (1).

Although the logic behind the physical causes of SAD is easy enough to understand, the biochemical characteristics of the disorder are extremely complicated. Depression usually occurs from a chemical imbalance in a person's brain. This imbalance can be the result of many factors, such as lack of sunlight, inability to manage stress, negative feelings, or genetic make-up. Scientists have discovered that all people who suffer from a form of depression have developed problems in their brain chemistry.

Through a system of electrical impulses and chemicals, the brain uses neurons to communicate with the body to convey feelings, thoughts, movement, and language. To pass electrical impulses from one individual nerve cell to another, neurons use chemical messengers called neurotransmitters that are contained in pouches at the end of each cell. After the pouches are signalled to release the neurotransmitters into the gap between nerve cells, the neurotransmitters should then "dock" on the next nerve cell at specific sites that send the message on. After this release, the neurotransmitters return to the cell from which they came in a process called "reuptake." In a depressed person's brain chemistry, there is a decrease in the number of neurotransmitters that are released or a failure of the neurotransmitters to "dock." Due to these malfunctions, chemical messages from the brain do not get sent, causing the depressed person to have abnormal reactions to his or her environment. Although these changes in brain chemistry can be attributed to many causes, scientists have found that heredity is a major factor, as nearly 50 percent of depressed people have one or both parents who have suffered from depression.

Probably the most important of neurotransmitters is serotonin, which controls moods of contentment and makes a person feel more calm and relaxed. While serotonin depletion can cause suicidal behavior and depression, high serotonin levels can also have dangerous effects, causing impulsive or aggressive behavior.

Symptoms

The symptoms of Seasonal Affective Disorder appear in the winter months and leave with the return of longer days of sunlight, in the spring. They include body aches and pains,