People who suffer from a stress disorder have a severe handicap in daily life. In addition, stress disorders are complex and consequently, hard to define and hard to treat. Semi-automatic assistance was envisioned that helps in the treatment of a stress disorder. Speech was considered to provide an excellent tool for providing an objective, unobtrusive emotion measure. Speech from 25 patients suffering from a stress disorder was recorded while they participated in two storytelling sessions. The Subjective Unit of Distress (SUD) was determined as a subjective measure and enabled the validation of the derived speech features. A regression model with four speech parameters (i.e., signal, power, zero crossing ratio, and pitch), was able to explain 70% of the variance in the SUD measure. As such it lays the foundation for semi-automated assistance for the treatment of patients with stress disorders.