Biology 202
2000 First Web Report
On Serendip

For one reason or another, I allow the whims of Mother Nature to determine how I think and feel. If I wake up and the sun is brightly shining through my window creating a beautiful mixture of dark and light shadows, I suddenly feel happy and look forward to the day ahead. On the other hand, if I wake up and look out onto another cloudy and cold day in February at Bryn Mawr, I have the aching desire to crawl back into bed and sleep the day away.

I am not alone in that my mood and disposition are determined daily during those first few moments in which I am awake. In fact, this phenomenon is shared by many. The general feeling of winter depression coupled with normal mood in the summer has been around for centuries, but it was not until the 1980s that it was characterized as a type of clinical depression (1). Psychologists have long been studying the effects of what they now refer to as Seasonal Affective Disorder (SAD), the biological condition associated with changes in weather patterns.

Can Seasonal Affective Disorder be considered a true medical condition? Everyone reacts to the changing seasons with corresponding changes in mood and behavior, but some experience more severe symptoms which alter their whole way of life. The symptoms of Seasonal Affective Disorder tend to first appear in late September when the days get shorter and the temperatures drop, and last until April or May.

Seasonal Affective Disorder is characterized by recurring periods of depression lasting for at least two successive years of seasonal change (2). Other symptoms include a voracious appetite involving a high carbohydrate craving and accompanied by a 10-20 pound weight gain, sleep problems, memory loss, suicidal thoughts, problems concentrating, and an overall lack of interest in or enjoyment of activities. Unlike other forms of clinical depression, Seasonal Affective Disorder involves the cyclical pattern of depression that comes as the amount of daylight hours decrease and disappears as the days get longer (1). SAD patients often have hypersomnia during the winter and become manic or hyperactive in the spring.

Can environmental conditions truly alter one's state of mind? A North American clinical research study administered to hundreds of thousands of people in the early 1990s revealed that 30-50% of the general public complained of symptoms related to seasonal depression. (3). The frequency of Seasonal Affective Disorder varies with geographic location, thus providing evidence that the environment in which you live may determine how you feel. As much as 30% of the people residing in northern states, including Oregon, Washington, and Alaska, experience SAD (4). Additionally, 10% of the population of northern New England states report symptoms of SAD (4). In stark contrast, less than 2% of the population of Southern California and Florida are afflicted with SAD, where the weather remains mild and daylight hours are longer throughout the year due to their close proximity to the equator (4).

Three out of four Seasonal Affective Disorder sufferers are women, but SAD affects men and children as well. According to a report in the Journal of the American Academy of Child and Adolescent Psychiatry, more than one million children may be afflicted (3). The typical age of onset is in the twenties, but other onsets are common during life changes such as puberty, middle age, and old age. After women pass through menopause, the numbers of men and women affected become equal.

As Seasonal Affective Disorder is a type of clinical depression, its treatment is similar to that of other depressive episodes, utilizing antidepressant and mood stabilizing medication and possible psychotherapy. In addition, since SAD is brought on by a decrease in the amount of sunlight one is exposed to, an effective means of treating this disorder is bright light therapy (BLT) or phototherapy (5).

Bright light has been shown to help elevate one's mood. In this particular form of treatment, the patient sits in front of a special fluorescent light box that produces light of an intensity 10 to 20 times higher than standard indoor lighting (5). Treatment is based on the interaction of light with the eyes, not the skin. For the majority of those who suffer from SAD, sitting in front of a light box for one half of an hour daily will be sufficient to alleviate the symptoms (5). The user does not have to stare at the light, but can watch TV or read; just allowing the light to reach the eyes.

Dr. Norman Rosenthal, the psychiatrist responsible for characterizing Seasonal Affective Disorder, also developed the field of light therapy. Light therapy regulates brain chemistry by controlling the levels of serotonin and melatonin in the body (1). Serotonin is a neurotransmitter believed to influence mood. Rosenthal believes that serotonin regulation is abnormal in people afflicted with SAD and that it can be corrected with more light (1). Additionally, serotonin levels can also be increased by a diet rich in carbohydrates, which explains the intense carbohydrate cravings of many SAD patients.

On the other hand, melatonin is a hormone synthesized and released in response to the amount of light entering our eyes. During the night, the pineal gland produces melatonin which makes us drowsy. At daybreak, the bright light causes the gland to stop producing this melatonin (5). On dreary winter days, there is not sufficient light to trigger the inhibition of melatonin. This particular mechanism demonstrates how the brain regulates and controls behavior through inhibition rather than activation.

Seasonal Affective Disorder and the impact of the environment on one's mood help to better link brain and behavior, but many questions remain. Is SAD caused by a change in the exposure to light? If so, are feelings of depression greatest during the beginning and the end of the winter season rather than during the dead of winter? In addition, how many Bryn Mawr students actually suffer from SAD? Many of us complain about feeling lousy and lethargic in the dead of winter, but could we all be afflicted with Seasonal Affective Disorder?

So, the next time you wonder why everyone around you seems to be down in the dumps- you can look to the weather outside for your answer, but please remember that it may not tell you the whole story.

WWW Sources

2) National Mental Health Association- Information about Seasonal Affective Disorder SITE,

3) NARSAD Researcher Sheds New Light on Seasonal Affective Disorder ,

3) Summary of Research on Seasonal Affective Disorder (SAD) ,

3) Outside In Information Sheet ,

3) Internet Mental Health Site ,

3) Information from your Family Doctor ,

3) UBC Mood Disorders Center ,

3) Seasonal Light/SAD Homepage ,

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