Involuntary emotional expression disorder (IEED), a distressing and potentially debilitating condition characterized by uncontrollable episodes of laughing and/or crying, causes extensive social and occupational dysfunction amongst patients. However, despite affecting more than one million people worldwide, IEED is often overlooked or misdiagnosed, and current treatments are compromised by uncertain efficacy. In this supplement we review the epidemiology and pathophysiology of IEED, and discuss new pharmacologic interventions which may afford opportunities for symptom control amongst IEED sufferers.

Although the uncontrollable episodes of emotion which characterize IEED were first described more than a century ago, a bewildering profusion of terminology has since confused and hampered the efforts of physicians to recognize and treat this condition. In the first article, John E. Duda, MD, examines the history of IEED in the medical literature, and evaluates the prevalence of the condition amongst patients in whom emotional or affective motor control has become dysregulated, either as a result of brain damage from neurological disease or as a result of brain injury.