[9급 국가직 영어 2018년 17번]

Insomnia can be classified as transient, acute, or chronic. Transient insomnia lasts for less than a week. It can be caused by another disorder, by changes in the sleep environment, by the timing of sleep, severe depression, or by stress. Its consequences such as sleepiness and impaired psychomotor performance are similar to those of sleep deprivation. Acute insomnia is the inability to consistently sleep well for a period of less than a month. Acute insomnia is present when there is difficulty initiating or maintaining sleep or when the sleep that is obtained is not refreshing. These problems occur despite adequate opportunity and circumstances for sleep and they can impair daytime functioning. Acute insomnia is also known as short term insomnia or stress related insomnia. Chronic insomnia lasts for longer than a month. It can be caused by another disorder, or it can be a primary disorder. People with high levels of stress hormones or shifts in the levels of cytokines are more likely than others to have chronic insomnia. Its effects can vary according to its causes. They might include muscular weariness, hallucinations, and/or mental fatigue. Chronic insomnia can also cause double vision.