Insomnia affects approximately 10 to 17 percent of the adult U.S. population.^1,2 In contrast to the occasional sleepless night experienced by most people, insomnia may be a persistent or recurrent problem^3,4 with serious medical complications, including anxiety, depression and multiple physical complaints.^4–6 The total cost of insomnia, including treatment, lost productivity and insomnia-related accidents, may exceed $100 billion per year.⁷

Definition and Etiology

Insomnia may be viewed as both a symptom and a syndrome. As a symptom, insomnia may develop secondary to an underlying medical, psychiatric or environmental factor. Several of these causal factors are presented in Table 1. In these cases, it is essential to identify and treat the underlying cause of insomnia. Misidentification of the underlying cause may result in ineffective or even harmful interventions, such as prescribing a benzodiazepine for patients with insomnia that is due to sleep apnea or substance abuse. In cases of symptomatic insomnia, the target of treatment is not the sleeplessness itself but the underlying disorder.

Primary insomnia is sleeplessness that is not attributable to a medical, psychiatric or environmental cause. The diagnostic criteria for primary insomnia from the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) are presented in Table 2.⁸ The diagnosis is based on the patients' subjective reports of their sleep patterns, including complaints of nonrestful sleep as well as difficulties with sleep onset or maintenance. Symptom severity must be sufficient to result in significant emotional distress or impairment in functioning. The disorder is chronic by definition (i.e., lasting at least one month).

The etiology of primary insomnia relates in part to psychologic conditioning processes.⁸ Most cases of insomnia develop initially in response to a medical or psychosocial stressor. As sleeplessness persists, the patient begins to associate the bed with wakefulness and heightened arousal rather than sleep. The patient may fall asleep easily outside the bedroom (i.e., when watching television or reading in the living room) but feel wide awake in bed. It is important to note that once this conditioning process has occurred, the patient's insomnia may persist long after the original psychosocial or medical stressor has been resolved.

Evaluation

A thorough clinical interview is critical for effective treatment of insomnia. A variety of medical, psychosocial and environmental factors that may cause insomnia must be ruled out (Table 1). Collateral interviews with the patient's sleep partner are also useful^9,10 to gather information regarding nocturnal events of which the patient may be unaware, such as apneic episodes, periodic limb movements, nocturnal myoclonus or fitful sleep.

An extensive review of the medical conditions that can cause insomnia is beyond the scope of this article. However, medical conditions should be considered in the evaluation of patients with sleeplessness.

A sleep diary is also important in the evaluation of insomnia.^9,10 A sleep diary is a questionnaire completed by the patient each morning to describe the previous night's sleep. Variables assessed by the diary may include time entering and leaving bed, sleep latency, total sleep time, number of awakenings and subjective assessment of the restfulness of sleep. Data from the sleep diary may help minimize distortions in sleep information recalled in the physician's office.

The usefulness of polysomnographic evaluation in cases of primary insomnia has been questioned because of its cost and the possibility that insomnia may be specific to the patient's usual sleep environment.⁹ However, polysomnographic evaluation may be considered when sleep-disordered breathing or periodic limb movement disorder is suspected or when behavior and psychopharmacologic treatments are unsuccessful.¹¹ It is not recommended for the routine evaluation of insomnia.¹¹

Pharmacologic Treatment of Insomnia

NONPRESCRIPTION DRUGS

A recent community-based sample of young adults indicated that approximately 10 percent had used nonprescription medications and 13 percent had used alcohol in the past year to improve sleep.¹ The active agent in many over-the-counter medications (such as Sleep-Eze, Sominex and Nytol) is one of the sedating antihistamines (e.g., diphenhydramine [Benadryl], doxylamine [Unisom]). While these medications are generally safe, they have anticholinergic side effects such as urinary retention, dry mouth and constipation. The half-life of these agents is variable, and their use can result in residual drowsiness. Both nonprescription medications and alcohol are only minimally effective in inducing sleep and may reduce sleep quality.¹⁰ Consequently, patients should be discouraged from using them on a routine basis.

MELATONIN

Melatonin is currently a popular remedy for insomnia. An entire issue of the Journal of Biological Rhythms (December 1997) was devoted to this topic. The family physician should anticipate questions from patients regarding this compound and its use as a sleep aid. Melatonin is a hormone secreted by the pineal gland and is purported to have sleep-inducing properties.¹² Although the effectiveness of melatonin remains controversial,^13,14 it has received attention in the treatment of insomnia caused by circadian schedule changes (i.e., jet lag, shift work). In these circumstances, melatonin successfully hastens adaptation to the new circadian schedule. Its effectiveness in cases of chronic insomnia that are not related to circadian schedule shifts is less clear.¹⁵

No serious adverse effects have been reported from the short-term use of melatonin. However, no systematic long-term studies of the use of melatonin have been reported.¹³ Although melatonin is a naturally occurring substance in the human body, its ingestion in pharmacologic dosages has the potential to induce undesirable side effects, such as sleep disruption, daytime fatigue, headache, dizziness and increased irritability.¹² In addition, standards of quality regarding purity, concentration and absence of harmful impurities are not regulated for melatonin as they are with prescription products. At this time, the use of melatonin for short-term adaptation to jet lag or shift changes would appear reasonable. However, given the availability of other safe and effective treatments for non–circadian-related insomnia, there is little basis for recommending the use of melatonin in these forms of insomnia until additional studies have been completed.

PRESCRIPTION DRUGS

The benzodiazepines are the medications most commonly prescribed for insomnia and have demonstrated efficacy in short-term treatment.² However, the wide range of metabolic half-life in these medications produces a variety of side effects, including physical dependence, sedation and impairment of motor abilities. Longer-acting medications such as flurazepam (Dalmane) and quazepam (Doral) are less likely to produce rebound insomnia but more likely to cause daytime sleepiness. Shorter-acting drugs such as triazolam (Halcion), temazepam (Restoril) and zolpidem (Ambien) are effectively eliminated by morning, decreasing the likelihood of residual daytime effects.

Triazolam has been removed from the market in several European countries because of multiple problems, including dependency, transient psychotic reactions, anterograde amnesia and rebound insomnia.¹⁶ Although zolpidem is not a benzodiazepine per se, it acts at the benzodiazepine receptor sites, and there are concerns that it may carry the same risk of dependence as the benzodiazepines.¹⁰

The traditional duration of hypnotic drug use for treatment of insomnia has been four weeks. Long-term use increases the likelihood of habituation and problematic withdrawal symptoms. Concerns about the use of benzodiazepines resulted in a drop of approximately 30 percent in benzodiazepine prescriptions for the treatment of insomnia between 1987 and 1991.¹⁷

A class of drugs that may offer an alternative in the treatment of insomnia is the sedating tricyclic antidepressants (amitriptyline [Elavil] and doxepin [Sinequan]). These medications are effective soporific agents even when given in low dosages that would be considered subtherapeutic for the treatment of depression. There is some concern that if these agents are used in the elderly, the risk of falling is increased. In addition, their use raises concerns regarding anticholinergic, cardiovascular and other side effects, along with the danger of potentially lethal overdose. Trazodone (Desyrel) may offer a safer alternative, although priapism is a potential side effect with this medication. Some commonly used medications and their dosages are listed in Table 3.

Psychologic Treatment of Insomnia

STIMULUS CONTROL THERAPY

The purpose of stimulus control therapy is to re-establish the connection between the bed and sleep by prohibiting the patient from engaging in non-sleep activities while in bed.^10,18 The instructions given to the patient are presented in Table 4. This treatment is easily administered by the family physician and has demonstrated efficacy.¹⁸

SLEEP RESTRICTION THERAPY

Sleep restriction therapy involves limiting the amount of time the patient spends in bed to the actual amount of time the patient usually spends sleeping.^10,18 For example, if the patient normally spends only four hours per night asleep, then the total amount of time spent in bed per night would be limited to four hours, regardless of the actual amount of time spent sleeping. This allows a sleep debt to accumulate that results in more rapid sleep onset on subsequent nights. When the patient is spending 85 to 90 percent of the time in bed asleep, the allowable time spent in bed is increased. Although somewhat more complex for the family physician to describe, sleep restriction therapy is an effective treatment for insomnia.¹⁸

SLEEP HYGIENE EDUCATION

Sleep hygiene education consists of a set of instructions regarding environment and lifestyle factors that affect sleep.¹⁸ Table 5 presents a typical set of sleep hygiene instructions. Sleep hygiene is not effective as the sole intervention for insomnia¹⁸ but is recommended as an adjunct to other forms of therapy.

Pharmacologic vs. Psychologic Treatment

Both pharmacologic and psychologic treatments are effective in the management of insomnia, reducing sleep onset latency by 15 to 30 minutes and reducing the number of awakenings by one to three episodes per night.¹⁰ Although pharmacologic agents act more reliably in the short term, psychologic approaches produce more durable results¹⁰ without the side effects associated with medications. Few studies have evaluated the effectiveness of combined pharmacologic and psychologic treatments, but some studies suggest that patients who use sleep medications benefit less from psychologic interventions.^19,20

Since the efficacy of pharmacologic and psychologic treatments for insomnia is comparable, it is recommended that psychologic approaches be used as the first-line treatment whenever feasible, given their greater safety and long-term efficacy.