When Winter Is No Fun
By Dr. Syed Amir
Bethesda , MD
The onset of winter, dipping temperatures, longer nights and shorter daylight hours, spawns a variety of emotions and feelings in us. Some find the cold weather exhilarating, spurring them on to outdoor activities and sports, while in many others the reduced daylight generates feelings of gloom and depression that occasionally get so serious as to require clinical intervention.
The condition is described as seasonal affective disorder (SAD) and has similar debilitating symptoms as those of severe jet lag. The malaise, however, dissipates with the arrival of summer.
It is not clear why some, especially women, are more prone to feeling depressed during winter. Humans have been genetically programmed to be dependent on the sun for life sustenance and exposure to sunshine generally has a benign, uplifting effect on us. The lengths of days and nights are determined by the earth’s rotation around the sun. As the sun gradually moves away from the Tropic of Cancer and closer to Capricorn, people in the Northern hemisphere start feeling the effect of approaching cold weather. December 21, often referred to as the winter solstice, is the shortest day of the year. Those living closer to the equator and tropics don’t experience large variations in the daylight hours during the year. For example, Karachi which is just above the tropic of Cancer (latitude: 24 53”), experiences relatively small seasonal differences in the length of the day than Islamabad (latitude; 33 40”), Peshawar or Kabul which are farther up in the North. In Karachi the difference between the daylight hours during winter and summers is about three hours, while in Islamabad and Kabul it is a little over four hours.
Unlike the populace in Karachi, people in Northern Europe, US or Canada, experience much larger seasonal variations in daylight hours. In Washington, the difference in winter and summer days is about 5 hours, while in Miami, Florida, well over thousand miles to the south and close to the tropic of cancer, it is only three hours. In Oslo, Norway, on the other hand, there is barely five hours of sunlight in the winter months, and the difference in summer and winter days is more than 13 hours. Further north in the Arctic Circle, the sun barely rises above the horizon in winter, causing an interminable dark night.
In a recent article in the Washington Post, Leslie Tamura had estimated that some 20 percent Americans start to feel downcast as the winter season approaches. In the US, the number of people affected by SAD in different states is related to the relative amount of sunshine they receive during winter months, with lower numbers of sufferers in sunny southern states and higher numbers in the north where sunshine is scare. The deleterious effect of long dark nights can be serious. Countries of Northern Europe that have long winters also have a high rate of alcoholism and suicide.
It is not known definitively what causes the darkened mood in some people in winter, but several ideas have been forwarded as possible explanations. The regulation of the human circadian rhythm or biological clock is associated with the solar day and any disruption can affect our heart, metabolic rates and a range of other life-related processes. Melatonin, an important hormone produced by the brain in humans and animals, is believed to be involved in the regulation of our sleep-wake cycles which are ultimately controlled by the central nervous system. The exact relationship of melatonin to sleep is not fully understood, but it is known that its production is induced by darkness which causes drowsiness and sleep. The hormone levels reach a peak at midnight and then gradually decline, ending with the daylight hours. There are indications that patients with SAD might have higher levels of melatonin in winter and normal levels in summer.
In patients with winter-induced depression, melatonin administration does not completely relieve the symptoms, suggesting that there might be additional factors involved. The chemical, serotonin, a neurotransmitter also produced by the brain, regulating sleep cycle, mood, emotions and even appetite, generates a sense of wellbeing. Sufferers of SAD have been found to have lower levels of serotonin in winter than others who do not suffer from it. An association seems to exist between low levels of serotonins and SAD that might explain why sunshine raises our spirit and sense of wellbeing and why people with low levels of this chemical are more susceptible to depression in winter.
How can we overcome symptoms of winter gloom? Many people find it helpful to be exposed to artificial light during the winter months that might work by stimulating the production of serotonin. There are other strategies to achieve this goal. For example, a diet that is rich in carbohydrate also raises the level of this chemical, but excessive consumption of sugars and starches have their own drawback. In extreme cases, drugs that are antidepressants have been successfully employed to treat this condition. In the end, the most important solace must come from the knowledge that winter darkness is always followed by bright, sunny and warm days, driving away the clouds of gloom and doom.
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