This chapter discusses the organization of human sleep by the brain mechanisms and specific sleep disorders that lead to disturbances in the brain mechanisms. Non-rapid eye movement (NREM) sleep is controlled by brainstem oscillators whose activation leads to the multiple physiological accompaniments of the NREM state. The dream is the unusual mental content that often accompanies REM sleep. As humans transition from wakefulness to sleep, characteristic physiological changes include decreases in respiratory rate, heart rate, and blood pressure. The domain of the insomnias benefits from thoughtful differential diagnosis, as the causation may be both multiple and obscure. The insomnia complaints that are comorbid with medical disorders include both sleep disturbances caused by medical symptoms, and also those sleep disturbances caused by the pathophysiology underlying the medical condition. Restless leg syndrome (RLS) and periodic limb movements of sleep (PLMS) are considered as sleep disorders.

The chapter first reviews evidence regarding the association between the psychiatric and medical disorders in children. It familiarizes clinicians with the range of medical or neurobiologic processes that might potentially contribute to the development of childhood psychopathology. The chapter hopefully sensitizes the clinician to the potential impact of underlying biologic processes on clinical psychiatric presentation. It provides a few guidelines for the clinician in the evaluation of children and adolescents presenting with psychopathology. Finally, the chapter summarizes a set of practical issues related to the evaluation and treatment of children with potentially co-occurring medical and psychiatric syndromes. Children with focal brain lesions face an elevated risk for psychiatric disorders, particularly behavior disorders. Based on this well-recognized association, an assessment of perinatal history and a neurologic examination have become an integral component of the comprehensive psychiatric evaluation in children and adolescents.

This chapter provides specific consideration to the problem of a pseudo-treatment-resistant depression (TRD), where a medical condition is misdiagnosed as major depression and so does not respond to antidepressant treatment. Amongst medical causes of depression the most frequent appear to be endocrine, in particular thyroid. The chapter presents the evidence supporting a more direct link between many neurological disorders and major depression. The background prevalence rate of major depression is already high in two groups of patients at risk for HIV infection, namely homosexual men and intravenous drug users. Psychiatrists and other mental health professionals can make an indispensable contribution by raising awareness amongst their colleagues of the importance and frequent neglect of major depression in many common medical disorders ranging from stroke to coronary artery disease. In these situations better recognition and treatment of major depression can only but make a valuable contribution to enhancing patient care.