Emotional lability is a disorder characterized by involuntary emotional displays of mood that are overly frequent and excessive, often the result of various neuropathologies.
Historically, emotional lability has been difficult to categorize as a distinct psychological disorder. The term is often used interchangeably with pseudobulbar affect (PBA), although PBA more generally refers to excessive emotions that may or may not correspond with the underlying mood. PBA also encompasses a broader range of emotions including anger and irritability, while emotional lability generally refers only to emotions characterized by laughing and crying.
Although the definitive cause is still unknown, most hypotheses point to the loss of voluntary, cortical inhibition over brainstem centers that produce the facio-respiratory functions associated with laughing and crying as the anatomical basis for this syndrome. This loss of cerebral control results in a dissociation of affective displays from the subjectively experienced emotional states.
A more specific neurological explanation cites bilateral corticobulbar motor track lesions as the main cause. The lesions uncouple cranial motor nerve nuclei and supranuclear integrative centers from their cortical control. Almost all cases of emotional lability involve neurological systems with motor functions, and associated lesions are always multifocal or bilateral. The most common neuroanatomic structures involved include the internal capsules, the substantia nigra, the cerebral peduncles, and the pyramidal tracts. The lesions are most commonly correlated with multiple sclerosis, Alzheimer’s disease, stroke, and traumatic brain injury.
The excessive emotional displays associated with the disorder can have a profoundly negative social impact. These displays often impair social and occupational functioning, lead to social phobias and withdrawal, and eventually become socially disabling.
To date, the inability to locate a definite cause for the disorder has impeded direction and treatment. Three scales measuring emotional lability have been frequently used and statistically validated: the Pathological Laughing and Crying Scale (PLACS), the Center for Neurologic Study-Lability Scale (CNS-LS), and the Emotional Lability Questionnaire (ELC). Attempts to reduce the symptoms of the disease often include anti-depressants and dopaminergic agents, with individual case reports suggesting some improvement in symptoms. However, no neuropharmaceutical treatment has conclusively shown to be effective in large, controlled trials.