Speaking behavior and voice sound characteristics in depressive patients during recovery

Based on a sample of 30 depressive patients, we have investigated the time course of recovery from depression in so far as this time course was assessable through changes in psychopathology syndrome scores and through changes in speaking behavior and voice sound characteristics. Specifically, our study design provided 6 repeated assessments over 2 weeks and at a fixed time in the morning each Monday, Wednesday and Friday, plus a final assessment at the patients' releases from hospital. Thus, we were able to determine the degree to which single-parameter approaches to speaking behavior and voice sound characteristics reflect the individual time course of recovery from depression. In this context, we could rely upon a calibration sample with repeated assessments on 192 healthy volunteers which yielded all necessary information concerning reproducibility and sensitivity of speech parameters. Our analysis revealed several prominent features of speaking behavior and voice sound characteristics to be closely related to the time course of recovery from depression. In particular, the parameters "F0-amplitude", "F0-6db-bandwidth" and "F0-contour" which assess important characteristics of a speaker's voice timbre, as well as the parameters "energy" and "dynamics" which assess a speaker's mean loudness and the variation of loudness over time, displayed consistently high correlations with depression syndromes. Moreover, the results of single-case analysis turned out to be in remarkable accordance with those of the cross-sectional one: in almost two-thirds of patients there existed a significant relationship over time between the global depression scores and major speech parameters. As to the remaining one-third of patients who did not fit the picture of high correlations between psychopathology and speech parameters, we found an overproportionally large number of non-improvers characterized by irregular patterns of slight improvement with subsequent deterioration, or of deterioration followed by slight improvement. In other words, one-third of patients displayed time courses of depression whose psychopathology is difficult to assess through standard exploration techniques. Accordingly, it is not clear whether the observed lack of correlation in these patients is due to insufficient data or to an actual discordance between the time development of psychopathology and that of speech parameters.