The Heterogeneity of Illness Behaviors in Patients with Medically Unexplained Physical Symptoms.

Purpose: To investigate the heterogeneity of illness behavior in patients with medically unexplained physical symptoms (MUPS), we clustered patients in regard to their degree of engaging in different aspects of illness behavior and identified related variables with these behaviors.

Method: A sample of N = 224 patients attending treatment in primary care with a history of MUPS (at least two symptoms) was investigated by analyzing different aspects of illness behavior with the self-reported number of doctor visits during the last 6 months and the Scale for the Assessment of Illness Behavior (SAIB; e.g., expression of symptoms).

Results: Two distinct clusters were identified by cluster analysis: a low (n = 106) and a high (n = 118) illness behavior clusters. The high illness behavior cluster exhibited a significantly higher rate of health anxiety than the low illness behavior cluster. Regression analysis revealed a particular effect of sex in the high illness behavior cluster: whereas being male was associated with increased illness behavior as measured by the SAIB, being female was linked to a higher number of doctor visits. Increased health anxiety was associated with the SAIB illness behavior in both clusters. Depression and anxiety did not show incremental associations with all aspects of illness behavior.

Conclusion: Knowledge of the pattern of illness behavior in patients with MUPS enables us to improve psychological treatments that directly address specific aspects of illness behavior or health anxiety. Differences between sexes in illness behaviors require more differentiated consideration in future research.