Skip to main content

Verified by Psychology Today


What Exactly Is Insomnia?

Understanding insomnia disorder.

Sleep in today’s culture has become mainstream for people to talk about and for the media to report on. Insomnia is a term that is often tossed around when someone says they are not sleeping well—but in fact, it may not be insomnia in the clinical sense. I was recently speaking with a news journalist who asked me, “What exactly is insomnia?” That question led me to write this article about insomnia disorder.

Insomnia disorder is the most common sleep disorder with a prevalence rate in the United States of 6-10 percent of the population and is defined by two classification systems. These two systems are The International Classification of Sleep Disorders, 3rd edition, published by the American Academy of Sleep Medicine, which is used by sleep specialists, and the Diagnostic and Statistical Manual for Mental Disorders, published by the American Psychiatric Association, which is used by mental health professionals. Both systems are in line with the general definition of insomnia disorder as 1) difficulty getting to sleep and/or staying asleep, when 2) circumstances allow for sleep and there is adequate time allotted for sleep, and 3) there is daytime impairment or distress related to the sleep disturbance. There is also a duration criterion. Insomnia must occur at least 3 nights per week and have been consecutively occurring for 3 months or longer.

Some things are important to note from this criteria. One is that the occurrence of insomnia symptoms, which are struggling to get to sleep and/or staying asleep followed by daytime impairment or distress, is not uncommon. This has occurred for most, if not all of us, at some point in our lives. Some examples of life situations that would cause difficulty sleeping would be an early morning flight, a new job, the loss of a job, a move, or the start of a relationship or marriage. Many factors can disrupt sleep on a short-term basis, and this falls under the category of an insomnia symptom. When the insomnia becomes prolonged and chronic and the person has adjusted to the initial insomnia trigger is when it may fall under the clinical criteria of an insomnia disorder.

Within the clinical sense, there can be other factors that might constitute a sleep disorder but may sound much like an insomnia disorder. A person that does shift work may experience trouble with sleep, but the culprit may lie in the shift work itself, as the person may be awake at times that they normally would be sleeping. Some examples of this would be a medical resident working the night shift in the ER and struggling to sleep in the morning following the shift, or a long-haul trucker driving at night when traffic is lessened and then has difficulty sleeping prior to the start of the next shift of driving. This falls under circadian rhythm sleep-wake disorder for shift work. This is also true for someone that frequently travels across time zones and has trouble sleeping according to their new external clock time; this falls under circadian rhythm sleep-wake disorder for jet lag. Another common issue that I see with patients in clinical practice is that someone is more of a night owl, which means they sleep an adequate number of hours but the timing of sleep is out of sync with the typical 9 to 5 schedule, and they experience difficulty adhering to an earlier schedule, thus missing school or work. A night owl may appear to have insomnia, but in actuality, it may be a circadian rhythm sleep-wake disorder for delayed sleep phase.

In our culture, we like to simplify things. This can have advantages, but one disadvantage of simplifying sleep issues is that we lose the richness of what may be driving the sleep disruption, thus the sleep issue gets mislabeled. This exemplifies the importance of knowing exactly what insomnia is. If you are struggling with sleep and your issue has occurred for an extended period of time and there is distress or impairment, it can be beneficial to discuss your issues with a sleep specialist. A sleep specialist can help identify the driving factors and the best course of action to get you to sleep better.

Board certified behavioral sleep medicine specialists can be found on the American Board of Sleep Medicine website.


American Academy of Sleep Medicine (2014). International Classification of Sleep Disorders, 3rd ed. Westchester IL, American Academy of Sleep Medicine.

American Psychiatric Association (2013). Diagnostic and Statistical Manual of Mental Disorders 5th ed. Washington D.C., American Psychiatric Association.

Ford DE, Kamerow DB (1989). Epidemiologic study of sleep disturbances and psychiatric disorders. An opportunity for prevention? JAMA 262:1479-1484.

More from Allison Siebern PhD, DAc, LAc, CBSM
More from Psychology Today
More from Allison Siebern PhD, DAc, LAc, CBSM
More from Psychology Today