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  • Updated 04.14.2023
  • Released 11.01.2000
  • Expires For CME 04.14.2026




Insomnia symptoms are the most frequent sleep disturbances and may affect more than 30% of the population; insomnia potentially affects nearly everyone occasionally. Ten percent become chronic, with negative consequences on mental and physical health. New models, new classifications, and new treatment options have emerged during the last few years and may change these negative trajectories correlated to insomnia.

Key points

• Diagnostic classification systems of insomnia have changed and finally define insomnia as a separate and independent condition known as “insomnia disorder” and not as a secondary condition.

• Symptoms of insomnia are not limited to the night; insomnia is now considered a “24-hour disorder” with nighttime and daytime symptoms.

• Hyperarousal, such as the hyperactivation of the stress system at a central and peripheral level, is the mechanism sustaining the cycle of chronic insomnia.

• Cognitive behavioral therapy for insomnia is the first-line treatment, but it is not so widespread. In some countries, pharmacological treatment is still the first option.

• Advances in pharmacological options have been made during the last 10 years, and the pharmacological armamentarium for insomnia is now wider.

Historical note and terminology

Insomnia, the difficulty in initiating or maintaining sleep, was first recorded in Egyptian medical papyri, with use of opium as a hypnotic to relieve insomnia and lavender as herbal sleep remedy in addition to its use for preserving mummies in the belief that death is eternal sleep (03). The ancient Indian text on Ayurvedic medicine, Charaka Samhita, written around 600 BC, describes herbal remedies for insomnia as well as nonpharmacological measures such as massage, warm bath, drinking milk, and listening to music. Although sleep disorders were known in ancient Chinese medicine, systematic description of these including insomnia was recorded in Huangdi Neijing (407-310 BC), with use of herbs and acupuncture for treatment. In Greek medicine, insomnia is reflected in Aristotle’s writings on sleeplessness in 350 BC (10). In Arab medicine, Avicenna’s Canon of Medicine, which was written in 1632 AD, described behavioral as well as pharmacological approaches for the treatment of insomnia.

More recently and until 2013, insomnia was considered and classified as a secondary condition to mental disorder or considered a primary form based on psychological factors. From 2013, major classification systems have classified insomnia as an independent disorder, emphasizing the concept of comorbidity compared to causality (primary or secondary). This new important classification was built thanks to the development of important models of insomnia. In the last 30 years, the notion has emerged that insomnia is a stress-related disorder with neurobiological, genetic, and psychological predisposing factors, and the 3Ps model, ie, predisposing, precipitating and perpetuating, has been developed (22). The neurobiological mechanism has been clarified and correlated to hyperarousal, and insomnia is emerging as a complex neurobiological disorder (18; 17; 24).

The International Classification of Sleep Disorders, 3rd edition (ICSD-3), was published by the American Academy of Sleep Medicine and is increasingly used by sleep physicians in the United States (01). The classification of insomnia disorders in ICSD-3 is a marked departure from that of prior systems. In ICSD-1 and ICSD-2, primary insomnia was further subtyped into psychophysiologic, idiopathic, and paradoxical (sleep-state misperception) insomnia disorders. The diagnostic reliability and validity of insomnia diagnoses, especially primary insomnia, have been challenged on the basis of several studies, and the ICSD-3 has included all insomnia diagnoses, ie, primary and comorbid, under a single, chronic insomnia disorder (19). The three categories now are:

(1) Chronic insomnia disorder
(2) Short-term insomnia disorder
(3) Other insomnia disorder

The Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5 and DSM-5 text revision), has been produced by the American Psychiatric Association and is more likely to be used by biological and psychiatric specialists (02). The DSM emphasizes the need for independent clinical attention of a sleep disorder regardless of mental or other medical problems that may be present. Two previous diagnoses—sleep disorder related to another mental disorder and sleep disorder related to another medical condition—have been eliminated, and greater specificity of coexisting conditions is provided for each of the 10 sleep-wake disorders defined, including insomnia. Starting from DSM-5, primary insomnia has been replaced with a diagnosis of insomnia disorder, a switch to avoid the primary/secondary designation when this disorder co-occurs with other conditions and to reflect changes throughout the classification.

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