Specific Effects of Depression, Panic, and Somatic Symptoms on Illness Behavior WINFRIED RIEF,PHD, ALEXANDRA MARTIN,PHD, ANTJE KLAIBERG,PHD, AND ELMAR BRA ¨ HLER,PHD Objective: In terms of restricted financial resources, the contribution of mental disorders to health care use and illness behavior is highly relevant. However, the specific contributions of panic disorder, depression, and somatic complaints to illness behavior in unselected samples is unclear. Methods: A representative sample of 2507 inhabitants of Germany was selected and grouped into people with panic disorder (30), somatic syndrome (102), major depression (24), depressive syndrome (77), and controls (2269). Assessment instruments were the complete version of the Patient Health Questionnaire (PHQ), the Scale for the Assessment of Illness Behavior (SAIB) as well as measures of health care use. Results: Although all clinical groups showed increased illness behavior, their impact was independent and specific. Subjects fulfilling the criteria of panic disorder showed the highest scores for illness behavior and health care use. People with mental disorders showed a greater increase in visits to general practitioners and medical specialists than to psychiatrists or psychologists. Regression analysis revealed that somatic complaints and depression have independent associations with illness behavior and health care use. Conclusions: Different mental and psychosomatic disorders contribute independently to health care use and other aspects of illness behavior. Key words: illness behavior, health care use, depression, panic, somatoform disorder. PHQ = Patient Health Questionnaire; SAIB = scale for the assess- ment of illness behavior; GP = general practitioner. INTRODUCTION I llness behavior describes the various aspects of how patients cope with their illness. The term illness behavior has origi- nally been introduced from Mechanic (1) who also empha- sized socioeconomic issues. Illness behavior covers features such as health care use, urging doctors to do investigations, taking medication, being disabled at work, avoidance of phys- ical activity, and expression of symptoms to family members and significant others. Pilowsky (2,3) introduced the term “abnormal illness behavior” to summarize behavioral aspects that might contribute to the maintenance of the disorder. Interestingly, illness behavior shows only moderate associa- tions with illness severity. This implies that people with the same illness show very different illness behavior, and it high- lights the fact that individual and social factors determine a major part of illness behavior. Anxiety and depression are important features associated with illness behavior. Not only in itself, but also in combina- tion with medical complaints, depression and anxiety are associated with higher health care costs (4 – 8). Another im- portant determinant of illness behavior is somatic complaints. The most frequent somatic complaints are rarely explained by organic diseases but have to be considered as “unexplained” or “somatoform” symptoms (9). Patients with somatization syndrome (multiple somatic complaints without a medical condition explaining the symptoms) constitute a major part of patients with extraordinary health care use (10,11). Patients with somatic complaints in combination with organic illness attributions tend to increase health care use (12,13). As so- matic complaints are an extremely frequent phenomenon (14), the health care relevance of this syndrome is substantial. To understand illness behavior, it should be kept in mind that not only health care use but also other aspects are relevant features contributing to the ways people cope with disorders. A recently published analysis of illness behavior (15) demon- strated that different aspects of illness behavior share only medium interrelationships around 0.31. In that study, we de- veloped a scale assessing the need for the verification of diagnosis, the expression of symptoms, the need for medica- tion and treatment, aspects of illness consequences such as sick leave from work, reduction of social activities, and phys- ical deconditioning, as well as the factor “body scanning” (attention focusing to bodily processes). The medium inter- correlation of these aspects highlights the fact that specific features of illness behavior can be very individual, and illness behavior is not a homogenous construct. Analysis of the association of psychopathological features with these different aspects of illness behavior is lacking. Another shortcoming of the studies investigating associa- tions between mental disorders and illness behavior so far is the focus on specific treatment settings. Most studies have investigated patients at specific institutions or primary care offices. This implies selection biases of the patient samples that could influence the results. Moreover, only patients al- ready showing health care use per definition are included in these studies. Therefore, we wanted to investigate associations between illness behavior with features of mental disorders in a representative sample of the general population. METHODS Subjects A representative sample of the general population of Germany was selected with the assistance of a demography consulting company (USUMA, Berlin, Germany). The area of Germany was separated into 306 sample areas representing the different structures of the country. After selection of a sample area, households of the respective area were selected per chance; finally members of this household fulfilling the inclusion criteria were again selected by chance. Inclusion criteria were German as a native language and age above 13. The sample was aimed to be representative in terms of age, gender, and education. A first attempt was made for 3855 addresses following a random- root procedure. All subjects were visited by an interviewer, informed about the investigation, and self-rating questionnaires were presented. The assistant From the Department of Psychology, University of Marburg, Marburg, Germany (R.W., M.A.); and the Medical School of the University of Leipzig, Leipzig, Germany (K.A., B.E.). Address correspondence and reprint requests to W. Rief, Clinical Psychol- ogy and Psychotherapy, Gutenbergstrasse 18, D-35032 Marburg, Germany. E-mail: rief@staff.uni-marburg.de This study was supported by grants from the German Ministry of Education and Research BMBF and from Pfizer Germany, Karlsruhe. Received for publication July 8, 2004; revision received January 19, 2005. DOI: 10.1097/01.psy.0000171158.59706.e7 596 Psychosomatic Medicine 67:596 – 601 (2005) 0033-3174/05/6704-0596 Copyright © 2005 by the American Psychosomatic Society