Introduction to Insomnia

Introduction

At any one time, a staggering one third of all humans are affected by insomnia. For many reasons, sleep-related complaints are also disproportionately higher in prevalence in medical practice. This malady, which was once thought to be an innocuous annoyance, is now known to impair normal human function, to cause a variety of medical and psychiatric disorders, and even to limit lifespan. For medical practitioners, therefore, the proper identification, clinical evaluation, and effective management of insomnia are of significant importance.

In this module, we take a systematic approach in informing the primary care practitioner in the evaluation and management of insomnia. In Normal Sleep, we begin with a foundation in normal sleep neurophysiology. The past few decades have seen a tremendous advance in our understanding of the central underpinnings of sleep and wakefulness. We now know that this seemingly quiescent state is the product of a complex array of interactions that produce a balance between wake-promoting systems on the one hand, governed by norepinephrine, serotonin, dopamine, acetylcholine, and histamine, and sleep-promoting systems on the other hand, governed by GABA and galanin and under the circadian influence of the hormone melatonin. Newly discovered neurotransmitters, the orexins/hypocretins, play a critical role in maintaining an orderly transition between these two states.

In Presentation and Diagnosis through Comorbidities and Associated Risks, we present the most recent diagnostic guidelines for insomnia. We explore key developments in clarifying the pathophysiology of insomnia, and explain how these have led to an evolution of our view of the relationship between co-occurring insomnia and medical/psychiatric disorders from a model of unidirectional causality to one of autonomous disorders interacting in a bidirectional fashion. We also delve into an in-depth review of the many consequences of this disorder.

In Presentation and Diagnosis and Treatment Options, we present some of the most important aspects of insomnia for clinical practitioners, i.e., its evaluation and management. We stress the importance of a thorough office-based evaluation, and present guidelines for this endeavor based on the most recent practice parameter statements. We emphasize the importance of treatment that is focused on underlying cause, as opposed to the uninformed entry into symptomatic management. In Treatment options, we explore the many available nonpharmacologic approaches and pharmacologic agents for the treatment of insomnia and provide an evidence-based approach in their selection and use. Whereas GABA receptor agonists have traditionally dominated the therapeutic armamentarium, we review novel and investigational agents with mechanisms traversing the receptor systems that are involved in the control of sleep and arousal, such as selective histamine H₁ receptor antagonists, selective melatonin receptor agonists, and dual orexin receptor antagonists. “Natural” compounds enjoy a significant allure by virtue of their widespread availability and the perception that they are safer than prescription medications for insomnia.

We explore the vast array of such products utilized for sleep-related complaints and provide empirical data to guide practitioners through the morass of claims regarding the benefits of these agents. Although less widely utilized than pharmacologic agents, cognitive behavioral therapy for insomnia (CBT-I) is of clear benefit, and is now considered the first-line intervention by most guidelines. We explore the principles underlying these techniques and guidelines in their implementation. We also review exciting new evidence demonstrating the lasting benefit of these therapies for extended periods of time following termination of treatment.

Throughout the module, we are guided by our main goal of providing practitioners with clinically relevant, evidence-based, and state-of-the-art information in the evaluation and management of insomnia. We have made a concerted attempt to ensure that our reviews are consistent with professional guidelines to the extent that current knowledge permits. Nevertheless, we remind our readers that scientific discovery is ongoing. Since the publication of this module certain guidelines and standards for treatment may already have changed. In addition, in clinical practice, medications may be used for indications and at doses that are not covered by the package label. Therefore, we advise readers to consult the peer-reviewed literature, as well as product labels, to obtain the most up-to-date information regarding recommended doses, safety profiles, indications, and other guidelines. Useful resources include the FDA website and FDA safety alerts.