Voice pitch measurements in schizophrenia and depression.

A monotonous voice is produced by schizophrenic patients whose expression of emotion is damped down and by patients with a severe degree of depression. Clinically, the distinction between these two diagnostic entities is virtually impossible to establish auditorily on the basis of voice quality alone. The laryngograph has been developed recently to record laryngeal activity. It was used to study voice pitch in a series of emotionally blunted and non-blunted schizophrenics, and retarded and non-retarded depressives. The frequency distributions of the laryngographic recordings were analysed to yield kurtosis scores. The group of retarded depressives had a significantly higher kurtosis score than the group of blunted schizophrenics. Hence this technique allows an objective distinction to be made between two kinds of monotonous voice produced by psychiatric patients. Furthermore, blunted schizophrenics had a higher mean kurtosis score than non-blunted schizophrenics, indicating that this measure can also be used as an objective index of blunting of affect in schizophrenia.