Background: The literature on acoustic measures of voice in depression is reviewed. Authors have separated results derived from studies of automatic speech, such as counting or reading, from free speech. Free speech requires cognitive activity such as word finding and discourse planning in addition to the motor activity of automatic speech. Also, results have been less ambiguous if homogeneous groups of agitated or retarded depressed patients were examined.
Methods: These distinctions are applied to the results of a 12-week double-blind treatment trial that compared response to nortriptyline (25-100 mg/day) with sertraline (50-150 mg/day). Twelve male and ten female elderly depressed patients and an age-matched normal control group (n=19) were studied. Patients were divided into retarded or agitated groups on the basis of ratings. Results from measures of fluency (speech productivity and pausing) and prosody (emphasis and inflection) are described.
Results: Depressed patients showed less prosody than the normal subjects. Improvement in the retarded group was reflected in briefer pauses but not longer utterances. There was a trend in the agitated group for improvement to be reflected in the utterance but not the pause measure.
Conclusions: Clinical impressions are substantially related to acoustic parameters. Temporal changes associated with depression appear to reflect the depressed state whereas prosodic features seem to reflect a depressed trait. Acoustic measures of the patient's speech may provide objective procedures to aid in the evaluation of depression. Limitations of the study are discussed.