The authors determined the prevalence of sleep disorders in a general population through a survey of 1,006 representative households in the Los Angeles metropolitan area. They found an overall prevalence of current or previous sleep disorders in adults of 52.1%. Specifically, they found a 42.5% prevalence of insomnia, 11.2% of nightmares, 7.1% of excessive sleep, 5.3% of sleeptalking, and 2.5% of sleepwalking. These conditions were often chronic and usually started early in life. Insomnia was more frequent in older people, particularly older women, and in people of lower educational socioeconomic status. Insomnia, nightmares, and hypersomnia were correlated with more frequent general physical and mental health problems.