The Effect of the Pineal Gland and Melatonin on Seasonal Affective Disorder
By, G. A. Odell
Northern Virginia Community College
February 26, 2006
As summer fades into autumn, those of us who live in latitudes a lot further away from Earth’s equator start to notice the changes in the seasons which are primarily the direct result of shorter days and longer nights. Feelings of winter fatigue and sluggishness are common among those who witness seasonal changes and a decrease in sunlight. However, for some individuals, the shift in seasons to the darker part of the year has a profound effect on their mood and energy levels – such a profound effect can cause what has been termed Seasonal Depression or Seasonal Affective Disorder. Such a disorder is closely related to the afflicted individual’s ability to receive sun light through the eyes’ optic nerves, which in turn affects the activities of the pineal gland and its secretion of melatonin – a major contributor to Seasonal Affective Disorder.
Seasonal Affective Disorder (SAD) is a clinical type of depression that affects the individual for half the year during the darker, colder months when daylight hours are decreased. In northern latitudes, these symptoms usually start as early as October and start to subside in March or April, returning the afflicted individual to a normal state of mood as daylight hours increase. (Rosenthal, 2006)
Symptoms of SAD include fatigue, increase in appetite and weight gain, craving of carbohydrates, social withdrawal, decreased sex drive, inability to concentrate, increased anxiety and need for sleep, and feelings of melancholy or despair. More severe cases of SAD may exhibit symptoms of Major Depressive Disorder with atypical features which can be characterized by a Major Depressive Episode, however, these symptoms are only present for half the year. (Rosenthal, 2006)
It must be noted that Seasonal Affective Disorder cannot be diagnosed as Major Depression since the depressive symptoms are triggered only by seasonal rhythms, whereas those suffering from Major Depression suffer from depressive symptoms year round – regardless of seasonal change. (Rosenthal, 2006)
Seasonal Affective Disorder seems to draw its root causes from the pineal gland. The pineal gland is an endocrine gland that modifies the activity of organs such as the endocrine pancreas, parathyroids, adrenal cortex, adrenal medulla, and gonads. Also called the Epiphysis, it is a small, reddish grey organ that makes up a part of the epithalamus. (Standring, 2005)
Previously thought of as “the seat of the soul” by French philosopher Rene Descartes in the seventeenth century, the pineal gland actually plays an essential part in the visual system. About the size of a pea in the mammalian brain, it responds indirectly to light by receiving messages along fibers from the suprachiasmatic nucleus nerve cells of the hypothalamus – which in turn receive signals from the optic nerve fibers of the eye. Suprachiasmatic nucleus is the major rhythm generating center (or body clock) of the body and is effected by melatonin secretion from the pineal gland. (Blakemore and Jennett, 2001)
The hypothalamus is essential in influencing certain aspects of behavior and survival. In humans, it is responsible for regulating emotions, nutrition, sexual desire, rhythms, and sleep cycles. The visual part of the hypothalamus also plays a major role in determining mood. The absence of light during the winter months can precipitate seasonal depression. (Blakemore and Jennett, 2001)
The pineal gland is responsible for the secretion of the hormone melatonin. This hormone is responsible for linking environmental light conditions with daily or seasonal patterns in the organism. Melatonin plays a major role in many mammals mating behaviors during certain seasons. Some mammals, such as deer, will start breeding during the autumn due to high levels of melatonin, whereas other mammals will start breeding during the spring as a result of low melatonin levels in the brain. (Campbell, Reece, Mitchell, and Taylor, 2003)
The pineal gland consists of cords and clusters called pinealocytes, which are associated with neuroglia cells that make up most of the gland. Pinealocytes are in charge of synthesizing melatonin from the amino acid, tryptophan. Melatonin is then stored in the pinealocytes’ dense cord vesicles before being excreted into the blood stream. (Standring, 2005)
The pineal gland’s effects are mainly inhibitory. Pineal secretions may reach their target cells via the cerebrospinal fluid or bloodstream. Some pineal hormones, such as melatonin, show circadian rhythms in concentration. The level of melatonin rises during darkness and falls during the day. (Standring, 2005)
Individuals suffering from SAD are more sensitive to abnormal increases in melatonin production than the average person, and start to display physical and emotional depressive tendencies in response to prolonged levels of melatonin. However, before one can start displaying symptoms of SAD, they must also be susceptible to depression as well as sensitivity to fluctuation in melatonin levels. “Research now underway suggests that SAD may come about through the collision of two vulnerabilities -- one to depression, the other to seasonality. People with SAD seem to be unique in that they have a kind of ‘biological calendar;’ they generate a distinct biological signal of lengthening nights, and that sets off a cascade of responses resulting in depression.” (Marano, 2006)
For those suffering from SAD, the nightly melatonin secretion is prolonged during the darkest months of the year. During the lighter months of the year, however, SAD sufferers do not experience any abnormal changes in melatonin secretion as they do during the other half of the year. A prolonged secretion of melatonin by 38 minutes can greatly influence seasonal mood in those suffering from SAD. (Marano, 2006)
This prolonged increase in melatonin production is probably the direct result of defects in the optic nerve. As sunlight weakens during the darker months, the optic nerves of those suffering from SAD require more sunlight in order to shut off melatonin production in the pineal gland, and the limited light of the darker part of the year is not sufficient enough to send such signals to that gland. (Marano, 2006)
In the United States, some estimates say that 11 million people suffer from SAD, and the symptoms usually start as the days shorten in autumn, are most pronounced between January and February, and start to subside as daylight hours lengthen in the spring. SAD is eight times more common in the Northern U.S. and Canada than in the Southern U.S. (Marano, 2006) About 75 to 80 per cent of SAD sufferers are women, who usually experience its onset in their 20s or 30s. (Johnson and Somers, 1994)
SAD is a disorder that persists for half the year at farther latitudes from Earth’s equator, and “is probably as old as patterns of human migration to latitudes distant from the equator.” The disorder is rarer for those living within 30 degrees of the equator where daylight hours are longer and brighter than they are at farther latitudes where there is less sunlight year round. (Marano, 2006)
Light therapy is probably the most common remedy for Seasonal Affective Disorder. High intensity, full spectrum light therapy is designed to “mock” real sunlight (such as 10,000 lux for half an hour) during certain periods of the day. The SAD sufferer can benefit from this type of therapy by subjecting their optic nerves to more intense light in order to reduce the production of melatonin when it is not needed. (Blakemore and Jennett, 2001)
Light therapy can also aid in brain chemistry by increasing the levels of production of the neurotransmitter serotonin as well as inhibit production of melatonin. Dr. Norman Rosenthal believes that the absence of light during the darker months of the year can also inhibit the production of serotonin (as well as increase melatonin). Lack of serotonin has been known to cause depression. (Johnson and Somers, 1994)
Other types of therapy for SAD include psychotherapy and drug therapy. Welbutrine XL influences the dopamine and norepeniphrine levels in the brain and is a common drug used to treat SAD patients. Other antidepressants used for SAD include selective serotonin reuptake inhibitors (SSRI) such as Prozac, and serotonin and norepinephrine reuptake inhibitors (SNRI) such as Effexor and Cymbalta. SSRI and SNRI drugs are designed to increase the levels of serotonin and norepinephrine in the brain, thus replacing the neurotransmitters inhibited as a result of SAD. (Rosenthal, 2006)
Other alternatives to light and psychotherapy include herbal supplements (such as St. John’s Wart), vitamins, and fish oil extracts. These alternatives have yet to be thoroughly tested in aiding SAD and other forms of depression, but there is a strong possibility that Omega-3 fatty acids found in fish oil, almonds, and walnuts may be beneficial for depression. (Rosenthal, 2006) Recent statistics indicate that “regular consumption of fish rich in omega-3 fatty acids may prevent the disorder. Last year researchers reported that northerly countries where fish consumption is high -- Iceland and Japan, for example -- are spared the expected high rates of seasonal affective disorder.” (Marano, 2006)
While the underlining causes of Seasonal Affective Disorder are very clear, a lot of research still has yet to be undertaken with regards to this disorder. Until recently, the role of the pineal gland was still a mystery, and while it is now evident as the source of melatonin, a lot is still to be learned about its full functions. The fact that there are now effective treatments available for SAD are very promising, and will continue to improve as more is learned about SAD, the role of melatonin, and other factors contributing to this disorder.
Cited References:
Campbell, N. A., J. B., Reece, L. G. Mitchell, and M. R. Taylor, 2003. Biology Concepts and Connections, Fourth Edition. San Francisco, CA: Benjamin Cummings.
Blakemore, C. and S. Jennett, 2001. The Oxford Companion to the Body. Oxford, NY: Oxford University Press
Johnson, R. and S. Somers, NIMH, JAMA Shed Light on Seasonal Affective Disorder, Psychiatric Times, 1994. http://www.psychiatrictimes.com/p940216.html Accessed January 19, 2006
Marano, H. E., The Season of SADness, Psychology Today Magazine, 2002. http://www.psychologytoday.com/articles/pto-20020801-000003.html Accessed January 6, 2006
Rosenthal, N. E., 2006. Winter Blues, Revised Edition. New York, NY: The Guilford Press
Standring, S., 2005. Gray’s Anatomy, The Anatomical Basis of Clinical Practice, 39th Edition. Spain: Elsevier
Copyright © G. A. Odell 2006
