SAD (Seasonal Affective Disorder) As A Result of the Lack of Sunlight?

ekoike's picture

Seasonal Affective Disorder As a Result of the Lack of Sunlight?

Around this time of year, when the days are shorter and the nights are longer (and finals time comes around), we often find ourselves in a “slump” and a mild depression gradually kicks in. During this time of year, you may find yourself eating and sleeping more as the temperature drops and night time hours grow longer. Although we often label and mask this type of depression as just a passing phase that will eventually fade, these and harsher symptoms are signs of Seasonal Affective Disorder (SAD). Seasonal Affective Disorder, or SAD for short, which was once skeptically received by scientists, is a type of depression that occurs every winter as the day light time shortens and causes over half-million people who are affected every year to feel socially withdrawn and depressed. So what biological and chemical process causes this form of seasonal depression to occur?

              In order for us to be able to fully interpret and understand the biological and chemical aspects of SAD, we must discuss the effects of both melatonin and serotonin on the brain. Melatonin, which is a brain chemical or hormone that is created from the amino acid tryptophan and stimulated by darkness, in combination with serotonin, which on the contrary is triggered by sunlight and combats depression, deeply influences the Circadian rhythm and regulation of various body functions. During these winter times when daylight hours are shorter and night time hours are longer, the secretion of melatonin and serotonin become unbalanced. Since melatonin is triggered immediately by dark light, the chemical is secreted in larger quantities than previous months and since serotonin is triggered by sunlight, the quantities decrease, causing a chemical imbalance and a decreased ability to combat seasonal depression.[1]

              When we discuss the SAD (Seasonal Affective Disorder) as a form of a clinical depression, we must make sure to distinguish it from other types of psychological disorders, such as bipolar depression, since SAD patients’ symptoms only manifest themselves during the winter months and disappear as the seasons change. In fact, many recent studies prove that those who suffer from SAD suffer only during those seasons with diminished daylight hours. One in particular, which was conducted at research stations in Antarctica showed that even individuals who didn’t fit SAD criteria showed an increase in depression over the winter months.[2] Although it is only a temporary seasonal form of a depression, we must be sure to clearly identify and treat this form of depression as a serious disorder that has various symptoms, such as mood swings, excessive sleep, irritability and impaired memory/concentration.

Although all humans deal with this form of chemical imbalance with the decreased amount of sunlight available, there is new evidence to prove that in fact the degree of depression is deeply determined in the body’s ability to react to the hormone change and the body’s inability to limit production of melatonin in the case of the SAD patients. In 2001, Dr. Thomas A. Wehr and Dr. Norman E. Rosenthal, psychiatrists at the National Institute of Mental Health came across significant discoveries which supported this concept. While studying two sets of patient groups (one with SAD and one without) for 24 hours in the winter and the summer, “they found that the patients with seasonal depression had a longer duration of nocturnal melatonin secretion in the winter than in the summer”[3].

So why did the normal patients have no additional melatonin secretion? Most scientists agree that the key to understanding differences in melatonin secretion levels can be explained by the variation in the amount of artificial light one is exposed to. Recent evidence proves that in fact by using artificial industrial lights, we can suppress the over-secretion of melatonin within the brain. In 1984, Dr. Norman Rosenthal, a psychiatrist at NIMH (National Institute of Mental Health) published articles that suggested bright light therapy as an effective tool for preventing chemical imbalances within the brain.[4]

In recent years, as a direct result of this and other recent studies which confirmed this conclusion, a form of artificial light treatment has been touted as a safe and effective way to treat SAD patients. In light therapy, the patient sits in front of a light box, which is a small portable box that contains florescent lights that emits a type of light that isn’t found in regular household lamps. The concept of the light therapy is that this artificial light mimics the effects of outdoor light and leads to a biochemical change in your brain.[5] Especially in the months of December and January, when there is a significant drop in daylight exposure, treatments such as the light box can suppress further production of melatonin and decrease the effects of seasonal depression. In addition to artificial light therapy, which is known as the most effective treatment to this form of depression, other forms such as anti-depressant medications and increased exposure to sunlight can help alleviate the symptoms of SAD.

Although Seasonal Affective Disorder or SAD was once not recognized as a serious form of depression, recent scientific advancements have shown how severe the side effects are for patients who suffer from this mental-chemical disorder. Due to the shortened daylight hours of the winter months, the unbalanced hormone levels of secreted serotonin and melatonin results and eventually leads to this form of depression. Through the study of this relatively recently discovered mental disorder, we can conclude that in fact our external surroundings heavily influence our mood fluctuations and personalities.

Just as in our recent lab about “Genes, Environment, and Selection”, where my partner Crystal and I discovered that in fact each plant has its optimal condition and environment that it can thrive in, we find that humans too need to have a certain chemical melatonin and serotonin balance through sunlight that must be achieved in order to function correctly. Similar to how the absence of these sets of environmental and external factors would cause an unbalance within the plant’s phenotype, without proper amounts of sunlight, SAD (Seasonal Affective Disorder) haunts and significantly affects the mental and emotional well-being of those who are affected. Instead of failing to treat it correctly as a serious form of seasonal depression, it is important to be aware of the psychological counseling and self-help through light boxes that are available to those who are suffering from SAD.

[1] Sheslow, David V., and Stephen L. Cosby. "Seasonal Affective Disorder." TeensHealth. Jan. 2007. Nemours Foundation. 18 Dec. 2007 <>.

[2] Wrigley, Diane. "Seasonal Affective Disorder." Infoplease. Pearson Education. 18 Dec. 2007 <>.

[3] Friedman, Richard A. "Brought on By Darkness, Disorder Needs Light." New York Times 18 Dec. 2007. 18 Dec. 2007 <>.

[4] Watkins, Carol E. "Seasonal Affective Disorder: Winter Depression." Northern County Psychiatric Associates. 11 Dec. 2004. NCPA MD. 18 Dec. 2007 <>.

[5] "Seasonal Affective Disorder: Treatment with Light Therapy." MayoClinic.Com. 3 Oct. 2006. Mayo Foundation for Medical Education and Research. 18 Dec. 2007 <>.


Neville Janet's picture

Seasonal Affective Disorder

Very strange in a country (South Africa) where we have lots of sunlight I have been diagnosed with Seasonal Affective Disorder. Could this be genetic as my ancestors are English and Scottish and Lithuanian.

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