Acoustic analysis in the differentiation of Parkinson's disease and major depression.

In its early stages, Parkinson's disease (P.D.) may be difficult to distinguish from major depression (M.D.) leading to inappropriate management. Both illnesses are characterized by psychomotor retardation. The neurovegetative symptoms used to diagnose M.D. are not specific and in P.D. may be due to the physical illness itself. Currently, differentiation of the two disorders relies on subjective clinical observation. Improved diagnostic accuracy based on more objective data is needed. To this end, this study used computerized acoustic analysis to contrast speech patterns in P.D. and M.D. The sample consisted of 30 P.D. patients without depression or dementia, 30 patients with uncomplicated M.D., and 31 normal controls, each 60 years of age or over. Of the acoustic variables studied, M.D. patients had significantly reduced rates of speech compared with P.D. patients. The data suggest that this temporal measure of speech may be useful in the differentiation of P.D. and M.D.