Understanding Involuntary Emotional Expression Disorder

I nvoluntary emotional expression disorder (IEED) is a neurologic condition characterized by uncontrolled or exaggerated episodes of crying, laughing, or other emotional displays without an apparent stimulus to trigger such responses. Associated with a number of neurologic conditions, it is considered to be a disorder of disinhibition of emotional expression rather than a disturbance of feeling, and is distinct from mood disorders in which feelings of happiness and sadness can also lead to uncontrollable laughing or crying. Characteristics of IEED have been described in the medical literature for more than a century, but the neuropathologic cause of the disorder remains unclear. There is, however, general agreement that IEED is the result of an injury to the neurologic pathways that control the expression of emotions. An estimated 1.5 million in the United States have IEED. However, given the fact that IEED is a relatively common disorder among patients with various neurologic conditions, the actual number may be even higher. Furthermore, IEED generally is thought to be underrecognized and under treated because clinicians are unfamiliar with the disorder. In addition, the language clinicians use to describe disorders of affect and disorders of mood does not clearly distinguish between the two. Several terms have been used previously to describe IEED, including pseudo bulbar affect, emotional lability, emotional incontinence, and pathological laughing and crying. This has led to confusion and inconsistency within the scientific literature, with preferences in terminology tending to vary among clinical specialties. Certain terms imply a neurological basis for the disorder while others suggest a psychiatric basis. The disorder will be referred to here as IEED, an umbrella term meant to encompass all of the nomenclature historically used to describe this disorder.