Theories That Explain Insomnia
Sleep researchers and experts continue to investigate what leads to the development of insomnia. It is well-known that insomnia often occurs in the setting of various social stressors (e.g., personal loss, social disruption), mental and physical health problems (e.g., heart disease, depression) and in those with a family history of the condition (see Risk Factors for Insomnia). However, this does not explain why insomnia actually occurs. There are several theories that have been proposed to explain its basis.1,2 One common theory suggests that insomnia is a state of "hyperarousal" where affected persons are physiologically and mentally activated. Studies in persons with insomnia have found increased heart rates, elevations in the stress hormone cortisol or greater amounts of fast brain activity around sleep onset. However, not all persons with insomnia exhibit evidence of "hyperarousal". Another theory proposes that insomnia is related to a problem with the control of sleep and wakefulness. There are a number of biological pathways that have been shown to be important in governing sleep and wakefulness. If some of these pathways are disturbed, insomnia may develop. Advanced imaging and electroencephalographic  techniques have shown that there are differences in brain function between persons with and without insomnia. Unhelpful behaviors and thoughts also are thought to be related to the development of insomnia. This is one of the principles underlying the use of cognitive behavior therapy for insomnia (see Behavioral Treatments for Insomnia). The figure below incorporates some of the more common factors proposed to explain the development of insomnia. As more knowledge is uncovered regarding the development of insomnia, this framework will evolve.
Adapted from Levenson et al.1
The 3P's of Insomnia
Many of the theoretical concepts used to explain the mechanisms underlying the development of insomnia can be summarized in a model proposed by Dr. Arthur Spielman in the 1980's. This model includes three key factors that contribute to insomnia: predisposing, precipitating, and perpetuating factors.3
Predisposing factors includes factors that are often out of our control, like our age and genetics, that make us vulnerable to sleeping problems. Lifestyle issues and medical conditions may be predisposing factors as well. Although predisposing factors may increase your risk of insomnia, it is not enough to cause insomnia. See Risk Factors for Insomnia for more information.
Do you find it more challenging to get restful sleep when you are stressed out or worried about an upcoming deadline? Precipitating factors are circumstances that trigger the first few nights of insomnia. It could be a stressful life event, a recent trauma, or medical treatments or conditions. Any event or activity that can make it more difficult to sleep at night may be a precipitating factor for insomnia.
In some persons with insomnia, they lay awake spending too much time in bed trying to fall asleep. Eventually, they begin to associate the activity of going to bed and the bedroom itself with wakefulness and frustration about not sleeping. This results in a vicious cycle by which attempting to sleep leads to worse insomnia, and therefore results in a perpetuation of the problem. This can be worsened by poor sleeping behaviors such as reading with an eReader, using a smartphone, taking a nap or drinking coffee near bedtime. (See In the Modern Era)