Insomnia is the feeling of inadequate or poor sleep because of one or more of the following: trouble falling asleep; trouble remaining asleep; awakening too early; or non-restorative sleep. For insomnia to be diagnosed, these symptoms must be present at least three nights per week and the sleep difficulty is present for at least one month. All of these symptoms can lead to daytime drowsiness, poor concentration, irritability, and the inability to feel refreshed and rested upon awakening. Some 50 to 70 million Americans have a sleep or wakefulness disorder, according to the Centers for Disease Control and Prevention.
Insomnia is not defined by the hours of sleep a person gets or how long it takes to fall asleep. Individuals vary in their need for and satisfaction with sleep. A feature of insomnia is that individuals experience distress or impairment in functioning as a result of their poor sleep.
Insomnia can be classified as episodic, persistent, or recurrent. Insomnia lasting from one month to three months is episodic. If the symptoms last three months or longer, the insomnia is said to be persistent. Insomnia is considered to be recurrent if two or more episodes occur within the space of one year.
The development and course of insomnia as cataloged by the DSM-5 include:
The onset of insomnia symptoms can occur at any time during life, but the first episode is more common during young adulthood. Less frequently, insomnia begins in childhood or adolescence. In women, new-onset insomnia may occur during menopause and persist even after other symptoms, such as hot flashes, have resolved. Insomnia may have a late-life onset, which is often associated with the onset of other health-related conditions.
Insomnia can be situational, persistent, or recurrent. Situational or acute insomnia usually lasts a few days or a few weeks and is often associated with life events or rapid changes in sleep schedules or environment. It usually resolves once the initial event subsides. For some individuals, perhaps those more vulnerable to sleep disturbances, insomnia may persist long after the initial event, possibly because of conditioning factors and heightened arousal. The factors that precipitate insomnia may differ from those that perpetuate it.
For example, an individual who is bedridden with a painful injury and has difficulty sleeping may then develop negative associations with sleep. Conditioned arousal may then persist and lead to persistent insomnia. A similar course may develop in the context of acute psychological stress or a mental disorder. For instance, insomnia that occurs during an episode of major depressive disorder can become a focus of attention, with consequent negative conditioning, and persist even after resolution of the depressive episode. In some cases, insomnia may also have an insidious onset without any identifiable triggering factor.
The course of insomnia may also be episodic, with recurrent episodes of sleep difficulties associated with the occurrence of stressful events. Chronicity rates range from 45 percent to 75 percent for follow-ups of one to seven years. Even when the course of insomnia has become chronic, there is night-to-night variability in sleep patterns, with an occasional restful night's sleep interspersed with several nights of poor sleep. The characteristics of insomnia may also change over time. Many people with insomnia have a history of "light" or easily disturbed sleep prior to the onset of more persistent sleep problems.
Insomnia complaints are more prevalent among older adults. The type of symptom changes because of age, with difficulties initiating sleep being more common among young adults and problems maintaining sleep occurring more frequently among middle-aged and older individuals.
Difficulties initiating and maintaining sleep can also occur in children and adolescents, but there are more limited data on prevalence, risk factors, and comorbidity during these developmental phases. Sleep difficulties in childhood can result from conditioning factors (a child who does not learn to fall asleep or return to sleep without the presence of a parent, for example) or from the absence of consistent sleep schedules and bedtime routines. Insomnia in adolescence is often triggered or exacerbated by irregular sleep schedules. In both children and adolescents, psychological and medical factors can contribute to insomnia.