Emotional changes with multiple sclerosis and Parkinson's disease.

Multiple sclerosis (MS) and Parkinson's disease (PD) are relatively common neurological disorders. Both disorders are chronic and progressive, produce varying degrees of physical disability, and result in characteristic neuropathological changes to a variety of subcortical brain structures. Patients with MS or PD also exhibit a higher prevalence of emotional disorders relative to other patient groups with comparable degrees of physical disability. The present review (a) examines specific methodological issues associated with research in this area, (b) describes the range and severity of emotional disorders in MS and PD, and (c) examines both endogenous and reactive explanations to account for the increased prevalence of emotional dysfunction in these two disorders. Suggestions for future research are offered, as well as implications for treatment.