Sleep is a universal characteristic of all higher-functioning animals. Although the purpose of sleep continues to be the subject of much debate, few would argue that a well-functioning sleep-wake cycle is essential for good health. The need to better understand and properly diagnose and treat disorders of the sleep-wake cycle has led to the emergence of sleep medicine as a medical field. In addition, the past decade has seen sleep medicine become a multidisciplinary subspecialty recognized by the American Board of Medical Specialties; it has also seen the establishment of fellowships accredited by the Accreditation Council for Graduate Medical Education.
Problems with sleep are common among patients with psychiatric illness. Several of the most common psychiatric conditions have abnormalities of the sleep-wake cycle as part of their diagnostic criteria. Furthermore, DSM-IV includes sections listing parasomnias and dyssomnias as primary disorders. Disruption of the sleep-wake cycle can exacerbate impairment in functioning caused by psychiatric illness and complicate the treatment of those illnesses. For this reason, the ability to identify and address abnormalities of sleep and wake are essential to providing good psychiatric care.
The processes underlying abnormalities of sleep and wake can be quite varied and can involve multiple organ systems. Common examples include maladaptive behaviors and poor sleep hygiene that lead to insomnia, neurological or metabolic abnormalities that cause restless legs syndrome, or respiratory abnormalities that result in sleep-disordered breathing. Any of these can cause poor sleep quality and result in impaired wakefulness.
Moreover, underlying psychiatric illnesses, or their treatment, can complicate the treatment of sleep disorders. For example, an anxiety disorder could make it more difficult for a patient with obstructive sleep apnea to use continuous positive airway pressure, or a sedating psychiatric medication might worsen the hypersomnia of a patient who has narcolepsy.
Proper diagnosis and treatment of disorders of sleep and wakefulness can prove challenging. The clinician must understand both physiological and psychological processes—as well as the interaction of the two. For this reason, psychiatrists are well suited to the task. The general psychiatrist is by no means expected to be an expert in treating disorders of sleep and wakefulness. With the rate at which the field is evolving, this proves challenging even for the sleep medicine specialist. Rather, a basic understanding of common abnormalities of sleep and wake is invaluable and can greatly enhance the care given to patients with psychiatric illnesses.