During the months of November to February, the days start getting shorter and colder, and the nights longer and darker. Climate changes seem to affect many people and they just can't understand why they tend to feel gloomy and miserable. This mood disorder is called winter depression, or Seasonal Affective Disorder (SAD).

According to Norman E. Rosenthal, the doctor who coined the term SAD in 1984, winter depression has a sound medical basis that involves changes in the body's mood centers brought on by shorter daylight hours and a lack of sunlight. Most depressive illness sufferers experience a sense of utter isolation and loneliness. But the fact that many people go through the same grumpiness during this time of the year provides a sense of comfort and assurance that they are not alone. As the clich? goes ?misery loves company.?

Based on statistics of SAD Association, 500,000 people in the United Kingdom experience some form of winter depression, while doctors have estimated that 20% of the population, or almost 2 million people, are affected in Sweden by this condition.

One of the most effective and clinically proven treatment for SAD is ?light therapy?, which has been shown to benefit some 80-85 percent of SAD cases. Simple as it may sound, the treatment actually involves more than just turning on a light and sitting beside it while twiddling your thumbs as you wait for that renewed energy to ?power up? your whole well-being.

The average domestic or office light emits a paltry 200-500 lux (a lux is a unit of illuminance,) whereas a minimum of 2,500 lux is required to alleviate the symptoms of SAD. In comparison, a clear summer's day can reach an intensity of 100,000 lux.

Based on these specs, a number of specially designed light boxes have been invented that emit precisely the right amount of illumination. Symptoms of SAD gradually subside by sitting in front of one for about 30 minutes to several hours, depending on the severity of the condition.

Light therapy may be the best treatment for SAD as far as symptoms are concerned. However, addressing the root causes of the condition may involve both anti-depressant drugs and psychotherapy treatments especially for those with severe symptoms.

Studies have shown that the incidence of SAD increases dramatically as you go 30 degrees of latitude further north or south, as the condition is virtually unheard of in the tropical countries. A movement or vacation trip to these countries in the equator may sound impractical but can definitely improve ones mood and well-being.

Watching movies that feature warm, sunny, summery climates show demonstrable improvements in mood. Research shows that any film with clear blue cloudless skies, palm trees and an absence of snow should qualify for a movie therapy.

The same mood-enhancing effect may result by simply watching outdoor sports like cricket or golf. However, over-exposure to snooker, darts, and indoor bowling has been found to bring on a state of depressive, trance-like catatonia that, in severe cases, culminates in complete mental health breakdown.