Insomnia: When You Just Can't Sleep
The literal meaning of insomnia is "not sleeping," and that fits its modern definition perfectly. Insomnia occurs when you have trouble going to sleep, staying asleep once you finally fall asleep (including waking up too early), or you sleep but are not refreshed by the experience.
According to the International Classification of Sleep Disorders (ICSD), the continuum of insomnia, as experienced by the patient, identifies three stages (mild, moderate, and severe). Mild insomnia means the patient often complains of either not getting enough sleep or not feeling as though sleep was restful. It isn't associated with functional impairment, but the patient can feel tired, restless, irritable, or anxious.
Moderate insomnia is very similar with two differences. It occurs when the patient always feels sleep was insufficient or unsatisfactory, and it causes mild to moderate impairment of daytime functioning. In severe insomnia, the impairment itself is also severe.
Many factors can work together to produce insomnia, and researchers have identified physical, psychological, and even social causes as contributors to the problem. The two main types of insomnia are differentiated as primary (not caused by any identifiable medical, psychiatric, or external environmental influence) and secondary (resulting from a physical or mental illness, or a defined sleep disorder).
Also called "conditioned insomnia," this is a particularly interesting condition, because not only does the patient complain of insomnia, but also of a high level of anxiety regarding the insomnia. In this disorder, a stressful event produces both somatized tension, which is a complex of physical stress responses (for example, increases in muscle tension and blood vessel constriction), plus a conditioned response to the inability to sleep.
The patient transfers worry about the stress to worry about the sleep problem, that worry makes the sleep problem worse, and the conditioned response occurs when the failure to sleep and the worry become self-reinforcing. Everything an unaffected person associates with sleep (the bedroom, lying in bed, thinking about sleep) becomes associated for the insomniac with wakefulness instead, completely the opposite of the desired effect.
Sleep State Misperception
Also called "pseudoinsomnia," this condition is diagnosed when a patient complains of insomnia, but that complaint cannot be objectively verified (which is not true of psychophysiological insomnia). When the patient spends a night in the sleep lab, the polysomnography reveals no insomnia, but the patient insists the insomnia was present.
There's no suspicion of malingering, because the complaints seem sincere and straightforward, and the patient presents no history or appearance of mental disturbance. It is clear the patient is convinced he is not sleeping, and equally clear he is sleeping. What is not clear is why sleep state misperception occurs.
Also called "childhood-onset insomnia," this type of insomnia lasts a patient's lifetime, and is thought to stem from faulty wiring of some neurologic component responsible for sleeping and waking. Possible culprits include overactivity on the part of the system that responds to stimuli, or insufficient activity in the parts that usually bring sleep on and prolong it.
It is even possible some idiopathic insomniacs fall at the low end of the normal distribution in terms of sleeping hours. These patients are called "natural short sleepers," and their sleep span is less than 75% of what is considered the normal amount based on age.
Also called "short-term insomnia," this type of insomnia is caused by some emotional disturbance, which can be a stress, personal conflict, or even a change in environment that has emotional importance. These environmental triggers are by no means always catastrophic or even negative. They can include events like starting a new school or job, pre-test anxiety, or being married the next day.
For a diagnosis of adjustment insomnia, the change in sleep has to be sudden and drastic, and it needs to coincide with the timing of the stressful occurrence. When the event is anticipated, insomnia appears, and when the event goes away, the insomnia goes with it.
Behavioral Insomnias of Childhood
This category is actually two disorders, according to ICSD: limit-setting insomnia and sleep-onset association insomnia. Limit-setting insomnia is quite simple: a child manages to delay his bedtime by various behaviors, and no one prevents him from doing so. The more often the child succeeds in postponing the enforcement of sleep rules (in bed, lights out, no talking, and so on), the more strongly "bedtime" is associated with not sleeping.
Sleep-onset association insomnia occurs when certain conditions have to be met in order for a child to fall asleep. Given a bottle or pacifier, or being rocked, may induce sleep anywhere, while being placed in bed without the other stimuli does not cause sleep.
Inadequate Sleep Hygiene
Simply put, this refers to bad sleep habits. Human beings really are creatures of habit, and if any of those habits are oppositional to sleep that can create a problem. There are a large number of factors causing this type of insomnia, but here are some examples.
Substances like nicotine and caffeine can make it hard to fall asleep, whereas alcohol can alter the quality of sleep or interrupt sleep. If your work requires deep thought or you exercise vigorously too close to bedtime, those practices make it hard to sleep. Is your bedroom temperature uncomfortable, do your pets bother you at night, or does your bedroom lack curtains?
Failure to correct those conditions may cause trouble sleeping.
Insomnia Caused By a Drug or Substance, or a Medical or Psychiatric Problem
There are a number of insomnias grouped under this heading. There are three main types of drug or substance insomnia.
Food allergy insomnia is defined as an allergic reaction producing at least two of these symptoms: agitation, torpor during the day, breathing problems, gastrointestinal disturbance, or irritated skin. It's often associated with cow's milk, and the patient finds it hard to fall asleep or stay asleep.
When the allergen is removed from the patients' diet, the symptoms abate.
Nocturnal eating/drinking syndrome seems to be a conditioned response. Children grow accustomed to being fed just before bed, and then wake in the night expecting another bottle before falling asleep again. The behavior is also seen in adults who wake for midnight snacks, and once the behavior is learned it becomes habitual.
Further disturbance of sleep occurs when the patient must wake up to go to the bathroom.
In dependency insomnias (specifically, hypnotic-, stimulant-, and alcohol-dependent insomnias), a drug the patient takes continually disrupts normal sleep. Sleeping medication that causes a rebound effect must be taken every night, or the patient will remain awake because the drug is missing. The longer the drug has been used, the harder it is to withdraw and still sleep.
Central nervous system stimulants like caffeine, amphetamines, or cocaine act directly to keep the patient awake. Some stimulants, like decongestants, are used for other medical purposes, and the wakefulness is an unwanted side effect.
Some people drink alcohol in order to be able to sleep, then develop a tolerance for it. The more they have to drink before bed, the more likely it is they'll suffer mild withdrawal symptoms (sweating, the head pain and dry mouth of mild dehydration) during the night that wake them up.
There are numerous medical illnesses that produce insomnia as a side effect. The ICSD divides these up into two categories, neurologic disorders and other illnesses. The neurologic disorders often affect the brain (as in dementia or cerebral degenerative disorder) or the central nervous system (like Parkinson's disease). Some are genetically linked (the fatal familial insomnias). Sleep-related epilepsy and sleep-related headaches can also cause insomnia.
Other diseases that cause lack of sleep include sleeping sickness, nocturnal cardiac ischemia, chronic obstructive pulmonary disease, sleep-related asthma or sleep-related . reflux, and fibromyalgia.
Finally, there are several categories of psychiatric disorder that can also interfere with proper sleep. Alcoholism, mood, anxiety, or panic disorders, and psychoses are all commonly associated with problems in the sleep-wake cycle, and in diagnosing any insomnia it is important to separate the psychiatric disorder itself from the disruption in sleep.
For information on treating insomnia, see our insomnia treatment page.