Leisha J Cuddihy PhD (Dr. Cuddihy of Pine Rest Christian Mental Health Services in Grand Rapids, Michigan has no relevant financial relationships to disclose.)
Antonio Culebras MD, editor. (Dr. Culebras of SUNY Upstate Medical University has no relevant financial relationships to disclose.)
Originally released November 1, 2000; last updated January 15, 2013; expires January 15, 2016
Notice: This article has expired and is therefore not available for CME credit.


Nearly everyone suffers from an occasional night of poor sleep. For many, that occasional problem can become persistent and bothersome and can cause us to struggle as we attempt to optimize our daily lives. Despite better insomnia classification and recent evidence-based clinical guidelines, some evidence suggests that current classification systems do not fully capture the range of subjective sleep complaints. Recent research has focused on evaluating existing treatments for patients with primary insomnia. With the growing evidence base for nonpharmacological interventions for insomnia, recent studies have also aimed to evaluate the efficacy of these interventions in a broader range of patient populations.

Key points


• Current diagnostic classification systems may not capture the full range of subjective sleep complaints.


• Compared to pharmacotherapy, cognitive behavioral therapy for insomnia is equally efficacious in the short term and has more durable effects.


• Nonpharmacological treatments for insomnia are efficacious in treating insomnia that is comorbid with other medical and psychiatric conditions.


• The choice of pharmacologic agents should be directed by symptom pattern, treatment goals, past treatment responses, patient preference, cost, availability of other treatments, comorbid conditions, contraindications, and side effects.

Historical note and terminology

Insomnia, the difficulty in initiating or maintaining sleep, has been known officially for at least 2000 years, reflected in Aristotle's writings on sleeplessness in 350 BCE (Kryger et al 1999). The nature of its variable consideration as a symptom, complaint, disorder, disease, or consequence of other primary disorders has contributed to the difficulty in creating an effective approach to diagnosis and treatment. Insomnia appears in several forms: (1) difficulty initiating sleep, (2) repeated or lengthy awakenings, (3) early awakenings, (4) inadequate total sleep time, or (5) poor quality of sleep as reflected by its consequences, including daytime sleepiness. Other factors that contribute to a difficulty in diagnosis are the issues of individual variation in sleep need, along with the difference between the subjective assessment and objective measurements of sleep in a given patient.

Unfortunately, the classifications and nomenclature used by physicians lack uniformity of approach. Three major classification systems are used by professionals: (1) The International Classification of Diseases (World Health Organization 1992), (2) The Diagnostic Instructional Manual on Mental Disorders, 4th Edition, and (3) The International Classification of Sleep Disorders - 2nd Edition (American Academy of Sleep Medicine 2005). In the ICSD-2, the classification of insomnia was completely revised and updated, with inclusion of adult and pediatric etiologies. A comparison among these 3 classification systems, including comparative tables, is available for the interested reader (Edinger and Means 2005).

The International Classification of Diseases is published by the World Health Organization and is now in its 10th edition. It is the most widely used classification system for reporting diseases and causes of death. Part of its widespread utilization is its mandatory status for official reporting in the 194 World Health Organization member states. The International Classification of Sleep Disorders – 2nd Edition (ICSD-2) was published by the American Academy of Sleep Medicine and is increasingly used by sleep physicians in the United States (American Academy of Sleep Medicine 2005). The Diagnostic and Statistical Manual of Mental Disorders (DSM-4) has been produced by the American Psychiatric Association and is more likely to be used by biological and psychiatric specialists (American Psychiatric Association 1994). Unfortunately, there is no uniform agreement or ability to match the various diagnostic categories in insomnia effectively across the 3 classification systems. In general, the ICSD-2 has more specificity, and the new reorganization makes it much easier to use. In addition, crosslinks to the ICD-9 coding system are now available. The updated ICSD-2 diagnostic classifications of insomnia, along with their ICD-9 code counterparts, are listed in Table 1. It is worth pointing out that although other sleep diagnoses (such as sleep-related movement disorders, circadian rhythm sleep disorders and sleep-related breathing disorders) might lead to a patient complaint of difficulty sleeping, these disorders are not classified as “insomnia” under this diagnostic rubric.

Table 1. ICSD-2 Diagnostic Classifications of Insomnia

ICSD-2 Insomnia Diagnosis

ICD-9 Code Equivalent

Adjustment insomnia


Psychophysiological insomnia


Paradoxical insomnia


Idiopathic insomnia


Insomnia due to mental disorder


Inadequate sleep hygiene


Insomnia due to drug or substance (excluding alcohol)


Insomnia due to alcohol use


Insomnia due to medical condition


Insomnia not due to substance or known physiologic condition, unspecified (nonorganic insomnia NOS)


Physiologic (organic) insomnia, unspecified


Despite the availability of 3 different classification systems for insomnia, one study suggests that a significant number of people with sleep complaints do not fit into any diagnostic category (Ohayon and Reynolds 2009). Ohayon and Reynolds found that in a survey of 25,579 participants in 7 European countries, nearly 40% reported some type of sleep complaint, whereas only 9% met diagnostic criteria for insomnia. The authors suggest that classification systems may need to be revised in order to more adequately identify and categorize individuals with sleep complaints.

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