Objective
The new DSM-5 Somatic Symptom Disorder (SSD) emphasizes the importance of psychological processes related to somatic symptoms in patients with somatoform disorders. To address this, the Somatic Symptoms Experiences Questionnaire (SSEQ), the first self-report scale that assesses a broad range of psychological and interactional characteristics relevant to patients with a somatoform disorder or SSD, was developed. This prospective study was conducted to validate the SSEQ.
Methods
The 15-item SSEQ was administered along with a battery of self-report questionnaires to psychosomatic inpatients. Patients were assessed with the Structured Clinical Interview for DSM-IV to confirm a somatoform, depressive, or anxiety disorder. Confirmatory factor analyses, tests of internal consistency and tests of validity were performed.
Results
Patients (n = 262) with a mean age of 43.4 years, 60.3% women, were included in the analyses. The previously observed four-factor model was replicated and internal consistency was good (Cronbach's α = .90). Patients with a somatoform disorder had significantly higher scores on the SSEQ (t = 4.24, p < .001) than patients with a depressive/anxiety disorder. Construct validity was shown by high correlations with other instruments measuring related constructs. Hierarchical multiple regression analyses showed that the questionnaire predicted health-related quality of life. Sensitivity to change was shown by significantly higher effect sizes of the SSEQ change scores for improved patients than for patients without improvement.
The previous diagnostic category of somatoform disorders has recently been replaced by Somatic Symptom Disorder (SSD) in DSM-5. This diagnosis is characterized by “distressing somatic symptoms plus abnormal thoughts, feelings, and behaviors in response to these symptoms” [1]. Importantly, the previous requirement that symptoms had to be medically unexplained has been removed and psychological symptoms surrounding the somatic symptoms have been added (SSD criterion B). These positive diagnostic criteria are advantageous inasmuch as the diagnosis is now based on the presence of certain phenomena, rather than the absence of a phenomenon (i.e., a medical explanation). DSM-5 defines a specific set of psychological processes as diagnostic criteria: Excessive thoughts, feelings, or behaviors related to somatic symptoms or associated health concerns as manifested by rumination and/or high level of anxiety about health or symptoms and/or excessive time and energy devoted to symptoms or health concerns. However, several psychological characteristics that previous research has also identified as potentially relevant, such as a self-concept of bodily weakness, are not explicitly mentioned [2] and [3]. Rief and Martin [4] suggest that the B criterion should be operationalized by a wide range of cognitive, affective, and behavioral characteristics to further evaluate the validity of SSD. Moreover, it remains unclear how the set of relevant psychological processes ought to be measured in research and clinical practice.
Previous research has demonstrated that psychological processes predict functional impairment, health care utilization, and course of disease in patients with somatoform disorders above and beyond the number of somatic symptoms [2], [5] and [6]. Whereas the number and severity of somatic symptoms can be assessed by the well validated Patient Health Questionnaire-15 (PHQ-15; [7], [8] and [9]), or its new brief version, the Somatic Symptom Scale-8 (SSS-8,[10] and [11]), different psychological characteristics of patients with a somatoform disorder can be measured with other instruments [12], [13], [14], [15], [16], [17], [18] and [19] — e.g., health anxiety with the Whiteley Index [20]. Thus far, however, no instrument has been specifically developed to assess attribution, emotional features, cognitions, illness behavior, and interactional aspects simultaneously for patients with somatoform complaints. The length and item heterogeneity of established instruments prevents the formation of combined sum scores or index variables. A single validated instrument that simultaneously assesses the range of psychological processes relevant to the diagnosis of somatic symptom disorder is needed.
We developed a self-report questionnaire based on the literature regarding psychological processes characterizing patients with a somatoform disorder [2] and [21] and on the basis of the official diagnostic draft that preceded the current DSM-5 SSD [1]. The result was the Somatic Symptoms Experiences Questionnaire (SSEQ; English version see Appendix A; original German version see Appendix B) which measures a broad range of these processes with 13 items (for more detail see 22). In addition to these 13 psychological items that constitute the scale score, the SSEQ includes two items regarding the existence of physical symptoms and the number of doctor visits during the past 6 months. To enable many possible applications, the first part of the questionnaire was designed to be used for the general population as well as for patients with somatic symptoms. The second part of the questionnaire was designed to assess the impact of somatic symptoms during the previous 6 months. The 48 preliminary items were based on the following psychological aspects: causal attribution of symptoms (e.g., organic or psychological), emotional aspects (e.g., health anxiety), cognitions concerning somatic symptoms (e.g., catastrophizing), illness behavior (e.g., body scanning), and problems while interacting with physicians. After a pilot test, the final 15 items were selected on the basis of a sample of 453 psychosomatic outpatients. A principal component analysis (PCA) of the 13 psychological items yielded a four-component solution: 1. Health-worries (5 items), 2. Experience of illness (2 items), 3. Problems while interacting with physicians (3 items), 4. Consequences of illness (3 items). The scale appeared to have promising psychometric properties such as high internal consistency (Cronbach's α = .89), higher scores in patients with somatoform disorders than other patients, and ability to predict poor health-related quality of life (HRQoL).
The aim of the present study was to verify the factor structure and reliability of the SSEQ in a new sample and to comprehensively validate the questionnaire. To this end, its ability to identify patients with a somatoform disorder, its construct validity, as well as its sensitivity to change were tested.
