Passage One Questions 61 to 65 are based on the following passage: Animals react to the changing seasons with changes in mood and behavior and human beings are no exception. Most people find they eat and sleep slightly more in winter and dislike the dark mornings and short days. For some, however, symptoms (症状) are severe enough to damage their lives and to cause considerable stress. These people are suffering from SAD. The symptoms tend to start from around September each year lasting until April, but are at their worst in the darkest months. The standard figure says that around 2% of people in Northern Europe suffer badly, with many more (10%) putting up with milder symptoms. Across the world the incidence (发生率) increases with distance from the equator (赤道), except where there is snow on the ground, when it becomes less common. More women than men are found having SAD. Children and young people can also suffer from it. The problem stems from the lack of bright light in winter. Researchers have proved that bright light makes a difference to the brain chemistry, although the exact means by which sufferers are affected is not yet known. As the cause is lack of bright light, the treatment is to be in bright light every day by using a lightbox or a similar bright treatment. (Going to a brightly-lit climate, whether skiing or somewhere hot, is indeed a cure). The preferred level of light is about as bright as a spring morning on a clear day and for most people sitting in front of a lightbox, allowing the light to reach the eyes, for between 15 and 45 minutes daily will be sufficient to alleviate the symptoms. The user does not have to stare at the light, but can watch TV or read a book, just allowing the light to reach the eyes. OUTSIDE IN have a complete range of suitable lights, all in line with the research findings from medical and academic facilities. They are all available on our pioneering HOME TRIAL SYSTEM. What does the last paragraph mainly talk about