Symptoms of insomnia often result from one of these causes. Insomnia is
associated more often with a psychiatric disorder, such as depression, than with
any other medical condition. Surveys suggest approximately 3% of the population
has insomnia symptoms that are caused by a medical or psychiatric condition.
Among adolescents and young adults, the prevalence of this form of insomnia is
slightly lower. 2% of the general population is affected by this type of insomnia.
Approximately 3.5% of all sleep-center patients are affected by this condition.