Clarifying the latent structure and correlates of somatic symptom distress: A bifactor model approach.

Distressing somatic symptoms are ubiquitous both in mental disorders and medical diseases. From a psychometric perspective, the structure of somatic symptom distress is unclear, and little is known about the strengths of associations to related constructs, such as health anxiety and somatosensory amplification. To clarify the structure of somatic symptom distress and to explore associations to health anxiety, somatosensory amplification, and functional somatic syndromes, data sets of 2 samples of college students from Germany (N = 1,520) and Switzerland (N = 3,053) were investigated with confirmatory factor analysis with robust estimation. A bifactor model (with 1 general and 4 orthogonal specific symptom factors-gastrointestinal, fatigue, cardio-pulmonary, and pain symptoms) revealed the best model fit. Medium-sized associations were found among latent factors of general somatic symptom distress, health anxiety, and depression. First evidence for the construct validity of the latent variables within the proposed bifactor structure was gained by observing (a) strong associations between the general somatic symptom distress factor and somatosensory amplification and (b) significant associations between both the general somatic symptom factor as well as the symptom-specific factors with functional somatic syndromes. The results offer a theoretically and psychometrically plausible model for the structure of somatic symptom distress and suggest a distinction between cognitive-affective and sensory aspects of symptom perception. The findings are compatible with current cognitive psychological and neuropsychological approaches to symptom perception and imply that somatic symptom distress is a multidimensional phenomenon that is both strongly linked to but also clearly separable from related constructs.