Over the course of the last 30 years there has been a great deal of research into sleep abnormalities in patients with major depression. However, only a small proportion of this work has focused on sleep continuity disturbance (as opposed to abnormalities in sleep micro- and macroarchitecture), despite insomnia being a defining feature of depression. The present article provides an overview of the data and suggests that insomnia and depression are separable entities, insomnia confers a risk for greater depressive morbidity, and targeted treatment for insomnia may influence the clinical course of major depression.

As the population ages and awareness of sleep disorders grows, issues that concern both sleep and aging are becoming increasingly important. The elderly appear to be particularly susceptible to a variety of different sleep complaints. At the present time, little is known regarding the mechanisms underlying the development of these disorders, despite some excellent research in this arena. This review summarizes the existing knowledge on this topic, focusing on insomnia, sleep apnea, circadian rhythm disorders, rapid eye movement behavior disorder, and periodic limb movements/restless legs syndrome.

Among the wide array of neurotransmitters and neuropeptides that mediate neuronal communication, γ-aminobutyric acid (GABA) has emerged as the canonical inhibitory signal, and extensive in vitro studies have identified an enormous diversity in the signaling capabilities of the GABA_A receptor. This review will focus on GABA_A receptor function as a target for insomnia therapeutics, which until recently have been dominated by classical benzodiazepines.