Causes of Insomnia

There are several causes for insomnia. Generally, causes for this condition can be separated into three categories: (1) insomnia due to a sleep disorder, (2) insomnia due primarily to physical medical condition, and (3) insomnia due primarily to psychiatric disorder.

Insomnia Due to Sleep Disorders

Psychophysiological Insomnia, Difficulty Initiating and Maintaining Sleep (DIMS)

The term psychophysiological describes the connection between the body (physiological) and the mind (psychological). People with psychophysiological insomnia have difficulty sleeping because they react to stress or physical illness with increased physiological arousal. This usually happens when a person does not resolve the stress-inducing factor in his or her life.

Psychophysiological insomnia is caused by somatized tension, or stress that is expressed in bodily dysfunction, and learned associations that prevent sleep. Consequently, sleep, the one environment that soothes and rebuilds the body, is undermined by stress and anxiety.

Eventually the activities and the environment associated with sleep—brushing one's teeth, turning off the light, lying still in bed—displace the original stress factor and lead to insomnia. Sleep onset insomnia or sleep maintenance insomnia may last years. People who associate anxiety with their conventional sleep environment typically find it easier to sleep in unfamiliar environments, such as a hotel room, a friend's house, or the couch, where sleep-preventive associations are absent.

Sleep-State Misperception

People with sleep-state misperception sleep adequately, but feel they do not. A disparity exists between the person's subjective description of a night's sleep and the objective measurement of the same night obtained in a sleep clinic. When asked about sleep, these people underestimate their total sleep time and overestimate the time it took them to fall asleep. Physicians speculate that this discrepancy results from an unclear perception of consciousness and difficulty distinguishing sleep from waking. During clinical testing, these sleepers often claim to have slept as little as one-half of the time that the polysomnogram readings indicate.

Obstructive Sleep Apnea (OSA)

In obstructive sleep apnea (OSA), the airway collapses during sleep due to lack of muscle tone. OSA does not usually cause sleep onset insomnia, and the sleeper does not usually recall OSA-related awakenings. However, a person with OSA may awaken from an apnea in the early morning and be unable to resume sleep. Occasionally, people who suffer from OSA complain of daytime sleepiness because of repeated sleep disturbances. See more about OSA.

Central Sleep Apnea (CSA)

Central sleep apnea is commonly associated with a cerebral vascular condition, congestive heart failure, and old age. Unlike OSA, there is no obstruction of airflow. During sleep, a person with central sleep apnea does not receive the stimulus to breathe; the respiratory musculature fails, breathing stops, and the person wakes up to resume breathing. There is a greater rate of insomnia and excessive daytime sleepiness in cases of central sleep apnea than in obstructive sleep apnea.

Sleep Hygiene and Environmental Sleep Disorder

Proper sleep hygiene is the foundation of rewarding sleep, and its assessment is the basis for treatment of any type of disordered sleep. Inadequate sleep hygiene consists of all the habits that are not conducive to sleep longevity, like late-night exercise, late-night stressful activities (e.g., balancing the checkbook right before bedtime), late-night consumption of alcohol or caffeine, sleeping with loud noise, and sleeping on a poor mattress. Practicing good sleep hygiene includes standardizing the sleep environment and using stress-reduction techniques.

Altitude Insomnia

Ascension to high altitudes, those greater than 4000 meters (approx. 2 miles), can cause acute insomnia. This is usually experienced by pilots and flight crews and is often seen in military trainees. Symptoms typically include headache, fatigue, and loss of appetite.

Adjustment Sleep Disorder

Adjustment sleep disorder usually describes insomnia related to acute, temporary stress (e.g., starting a new job), preoccupation (e.g., thinking about a problem), or trauma (e.g., experiencing loss). Insomnia resolves when the stress factor is resolved or when the person acclimates to the new situation.

Limit-Setting Sleep Disorder

This sleep disorder is experienced by children. It is caused by a parent's inability to enforce a consistent bedtime for the child. Although the child usually sleeps adequately after going to sleep, getting out of bed, stalling, or confusion over fluctuating bedtimes can prevent a child's falling asleep comfortably.

Sleep-Onset Association Disorder

This condition is also most common in children. A child may need a set of cues to fall asleep, such as a pacifier, an audible television or radio, or a parent rocking him or her to sleep. If the cues are not present, the child has difficulty falling asleep and resuming sleep once awakened. Adults also may rely on specific sleep cues, but these are usually relevant to proper function, like the use of an alarm clock or two pillows.

Food Allergy Insomnia

Food allergy insomnia usually begins in infancy and resolves between the ages of 2 and 4. For example, an infant who is allergic to cow's milk usually has symptoms such as rash, shortness of breath, or gastrointestinal upset. Any one of these symptoms can compromise sleep for infants who need a lot of it. Adults rarely experience food allergy insomnia.

Medication-Dependent Sleep Disorder

Insomnia may arise when a person who takes chronic medications, like hypnotics and antidepressants, stops taking them or develops a tolerance for them. For this reason, physicians indicate a gradual reduction in dosage of long-term medications.

Stimulant-Dependent Sleep Disorder

There are a variety of drugs with stimulant properties that can cause insomnia, including pseudoephedrine, beta-2 agonists (bronchodilators), decongestants, theophylline, antidepressants, caffeine, thyroid medications, and nicotine. Over-the-counter medications with stimulant properties should be avoided prior to bedtime.

Alcohol-Dependent Sleep Disorder

People who depend on alcohol to help them sleep may experience insomnia when they don't use it. Alcohol, whether abused or not, negatively affects sleep quality and duration. See alcohol abuse and dependence.

Toxin-Induced Sleep Disorder

Toxins, like heavy metals and toxic chemicals in the blood, can cause insomnia.

Time-Zone Change (Jet Lag) Syndrome

Rapid transmeridian travel desynchronizes circadian rhythm and leads to jet lag, which may cause insomnia or excessive sleepiness. A person can shift their biological clock only by one to two hours a day. As a traveler rephases his or her biological clock to a new time zone, he or she may experience temporary sleep onset insomnia or sleep maintenance insomnia. See more about jet lag.

Shift Work Sleep Disorder, Shift Work Change (SWC)

People who work alternating shifts may develop insomnia because of a continually fluctuating sleep-wake schedule. For example, if a person works five nights a week and then works a day schedule for the next days, insomnia may result from changes in circadian rhythm. See more about shift work.

Irregular Sleep-Wake Pattern

Irregular sleep-wake pattern disorder may affect the elderly, people with central nervous system disorders (e.g., head injuries, dementia), and people who are bedridden or institutionalized, all of whom tend to have less concrete sleep-wake patterns because there is no demand to go to work, go to school, and so on. In these cases, sleep-wake patterns do not necessarily follow a routine.

Delayed Sleep-Phase Syndrome (DSPS)

In delayed sleep-phase syndrome (DSPS), the circadian rhythm is not synchronized with conventional sleep-wake periods. People with DSPS find it impossible to go to sleep before midnight and usually do not fall sleep until at least 2 a.m. They find it difficult to awaken in the early morning, despite mainstream society's demand to do so. If allowed to sleep eight hours, they feel refreshed. See more about DSPS.

Advanced Sleep-Phase Syndrome

People with advanced sleep-phase syndrome may find it impossible to stay up past 8 p.m., and they usually wake up very early. This is common in the elderly.

Non-24-Hour Sleep-Wake Syndrome

Non-24-hour sleep-wake syndrome is a rare disorder in which a person's circadian rhythm progressively signals sleep later each night. Bedtime might move from 11 p.m. to midnight one night and from midnight to 1 a.m. the next, and so on around the clock. The sleep period is usually of normal duration when circumstances allow. However, this condition poses problems for people who must wake up at the same time every day. This syndrome is usually a complication of structural brain lesions.

Nocturnal Leg Cramps

Painful cramps in the legs (charley horses) and feet during sleep are common in the elderly. The cause of leg cramps is unknown. The pain wakes the person up and can cause sleep maintenance insomnia.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 30 Nov 2000

Last Modified: 22 Sep 2015