Empirical foundations for the diagnosis of somatization: implications for DSM-5

The aim of this study was to develop empirically validated criteria for the diagnoses of clinically relevant somatization.

This study was performed in a population-representative cohort consisting of 461 males (47.8%) and 503 females (52.2%), with an average age of 55.8 years (s.d.=11.1). Somatization, anxiety and depression were derived from the Composite International Diagnostic Interview. Mplus was used to perform confirmative factor analyses on the current DSM-IV symptom groups; on alternative symptom clusters previously suggested; and to perform latent class analysis in order to define an empirically derived cut-off for somatization.

The existence of symptom groups as described in DSM-IV was not supported by our data, whereas a differentiation between cardiopulmonary, musculoskeletal, gastrointestinal and general somatic symptoms did fit our data. Latent class analysis revealed two classes characterized by few (n=859) and many (n=105) symptoms. The class of subjects could be approached by a simple cut-off of four functional symptoms (sensitivity 79%, specificity 98%, positive predictive value 82%, negative predictive value 97%) regardless of the number of organ systems involved.

This study in a large population-representative cohort suggests that a simple symptom count can be used as a dimensional diagnosis of somatization. In those instances in which a categorical diagnosis is preferred, a simple cut-off of four out of 43 functional symptoms best fitted our data. We did not find any added value for incorporating the number of symptom clusters into the diagnostic criteria.