【正确答案】Key points: Insomnia is difficulty falling asleep or staying asleep. Insomnia can be caused by emotional distress. It can be caused by stress from a single event, such as job loss or change, death of a loved one, or moving. Long-term insomnia may be caused by chronic stress or depression. Insomnia can have physical causes, such as discomfort or pain due to illness or injury. The consumption of coffee or alcohol may cause insomnia. Insomnia can be related to environmental factors such as noise, light, or extreme temperatures. Other causes are jet lag and a change in work shift.

【答案解析】[解析] Many people experience insomnia, difficulty falling asleep or staying asleep. There is no single cause of insomnia, as several different factors----emotional, physical, and environmental--can interfere with sleep. A common cause is emotional distress. This can he related to a single specific event. For example, there might be significant stress caused by a job loss or change, the death of a loved one, or moving to a different place. Insomnia caused by a single event is usually short-term, lasting from days to weeks. Long-term insomnia, on the other hand, is a recurring problem and may be caused by chronic stress, depression, or other health issues. Insomnia can have physical causes, such as discomfort or pain due to illness or injury. Chronic back pain is a common cause. Also, what you consume can interfere with your sleep-- drinking too much coffee, for example, or drinking it too late in the day. Alcohol can affect your sleep patterns. At first, alcohol might make you feel sleepy, but after its effects wear off, it may actually cause you to wake up during the night and have trouble getting back to sleep. Finally, insomnia can be related to environmental fact:ors such as noise, light, or extreme temperatures. Many peopie can't sleep during hot, humid summer weather. Other factors that throw offyour normal sleep schedule are jet lag or switching from the day shift to the night shift at work. Using points and examples from the lecture, explain some of the common causes of insomnia.