Published online Mar 19, 2026. doi: 10.5498/wjp.v16.i3.113646
Revised: October 6, 2025
Accepted: November 24, 2025
Published online: March 19, 2026
Processing time: 181 Days and 1.5 Hours
Voice is individual and therefore several studies consider voice as a biomarker of health. Focusing on the change of voice parameters of depressed patients can provide an additional, objective measurement of the patient’s individual progress during psychotherapy. This retrospective study is focused on the analysis of voice parameters, specifically prosodic parameters, gathered from sessions and real-world data out of the Munich psychotherapy study (MPS).
To investigate the prosodic parameters of patients with depression, their change over a long-term therapy and correlate them with Beck depression inventory (BDI) data. The analysis on the prosodic parameters aims to find, if and to what extent, a change in the patient’s voice can be discovered and identified. This data is then correlated with already available BDI data of each individual patient. The hypothesis is that voice expression is impacted by depression and changes with the state of depression.
We performed a retrospective investigation of n = 25 patients, who originally participated in the MPS, and their change in prosodic parameters. An analysis of the mean fundamental frequency fo and its standard deviation was performed on six psychotherapy sessions per patient, divided into three sessions at the beginning of the therapy and three sessions at the end of the therapy. The technical analyses on the voice part have been conducted with Praat, a phonetic analysis software developed at the University of Amsterdam.
The mean fundamental frequency was fo,mean = 183.1 Hz at the beginning and fo,mean = 187.8 Hz at the end, in a compounded group of all patients (men and women). The average BDI of all patients at the beginning was BDImean = 29.96 and BDImean = 9.6 at the end. A positive influence of psychotherapy can be seen in the majority of patients not only in a reduced BDI rating, but also in an increased baseline frequency.
With regard to the clinical picture of depression, its recognition and constant monitoring during therapy, it is important to exhaust all possibilities and examine additional relevant data. Prosodic characteristics can make a contribution here for various reasons. On the one hand, a person acts unconsciously via and through their voice and emotional states become detectable. On the other hand, voice can be represented in objective parameters and is therefore suitable for analyzing individual characteristics and changes. Dealing with the topic from the perspective of psychotherapy therefore seems unavoidable, as an additional component is included in the holistic view of the person.
Core Tip: Voice is a central component in interacting with the world and a major factor in defining the relationship between patient and therapist. The complex system enabling us to produce a vocal tone is influenced by several physiological components and transports information about our feelings and emotions. Especially for patients with depression the voice is often described as muted and monotone. This research initially provides theoretical background and then focuses on the evolution and change of the fundamental vocal frequency of patients with depression during long lasting psychotherapy. Therefore, a method was created to identify the fundamental frequency of sequences of sessions recorded within the Munich psychotherapy study and applied throughout sessions of 25 individual patients. The phonetic analyses were performed using appropriate phonetic software. The output of the analysis is crosschecked with the output parameters [Beck depression inventory (BDI) for depression] and converted into a formula to calculate a ratio between fundamental frequency and BDI rating scores. Results are shown on an individual basis for specific patients and evaluated for the overall scope and in an overall context.