Psychobehavioral B-Criteria of Somatic Symptom Disorder Are Associated with Somatic Symptom Reporting in a Large Sample of Psychosomatic Outpatients Open Access

Somatic symptoms poorly correlated with underlying disease pathology are highly prevalent, disabling, and costly [1]. As a disease entity, such symptoms are covered by the somatic symptom disorder (SSD), which was introduced in the fifth revision of the DSM [2]. The diagnostic category SSD is defined by the presence of one or more chronic somatic symptom(s) that cause significant distress and functional impairment in daily life (A-criteria), accompanied by specific psychological factors (B-criteria) [3]. When applying these proxy diagnostic criteria for SSD in general population studies, the mean frequency was 12.9% (CI 12.5–13.3%). Studies examining prevalence based on standard interviews are missing [4].

One of the main objectives in redefining somatoform disorders as SSD was to deemphasize whether the symptoms were attributable to another underlying medical condition, thereby moving away from a diagnostic approach that relied mainly on excluding other causes [3, 5]. To address this objective, the DSM-5 introduced specific psychobehavioral factors as essential criteria of the diagnosis. These “B-criteria” encompass cognitive, affective, and behavioral disturbances associated with somatic symptom reporting. Specifically, these criteria involve an individual experiencing disproportionate and persistent thoughts regarding the severity of their symptoms, persistently elevated levels of health anxiety, and excessive amounts of time and energy devoted to these symptoms [6].

Thus, the B-criteria are central to the definition and diagnosis of SSD as a mental illness. Importantly, they enable the identification of patients at risk for prolonged symptoms and reduced quality of life [7‒10]. These set of psychobehavioral factors also form the core construct of the Somatic Symptom Disorder-B-Criteria Scale (SSD-12) [11, 12]. The scale has been shown to be valid and sensitive to change in inpatients, with an improvement in somatic symptoms unexplained by the underlying disease pathology [13]. Furthermore, exploring the association between psychobehavioral criteria and levels of symptom reporting is of key importance. This association has garnered substantial attention from scholars and practitioners alike, as it holds potential implications for understanding the interaction of underlying psychological factors with the perception and reporting of somatic symptoms [14‒17].

The role of consented B-criteria compared to other potential psychobehavioral factors in their association with somatic symptom reporting is still being questioned [4, 17, 18]. Numerous psychological risk factors such as emotion regulation deficits, body checking, and extraversion have been suggested to contribute to a “psycho-bundle” in SSD, warranting further examination in clinical and population settings [17]. In line with this task, a recent review by Löwe et al. [4] discussed the validity of the B-criteria. The authors identified the need to further explore the relevance of these and other psychobehavioral criteria as a major research gap in SSD research.

To fill this gap in understanding, we investigated the relationship between the B-criteria and other relevant psychobehavioral factors with somatic symptom reporting in a substantial sample of individuals receiving treatment for psychosomatic conditions. We analyzed the data of 6,491 patients who attended an outpatient center specializing in the treatment of psychosomatic disorders over a time period of 12 years. We hypothesized that the established B-criteria of SSD were associated with somatic symptom reporting in our large sample, providing further evidence for the diagnostic concept of SSD as a combination of somatic symptom reporting and specific psychobehavioral factors. As part of exploratory analyses, we also investigated potential additional criteria that may be associated with symptom reporting and could provide further insights into the underlying mechanisms.

Reporting of the study followed the STrengthening the Reporting of OBservational Studies in Epidemiology (STROBE) guidelines for observational cross-sectional studies.

This was a retrospective, cross-sectional observational study of individuals presenting to a large psychosomatic outpatient center run by the largest public health insurance company in Germany, the general health insurance scheme (AOK) Northeast. During the examination, 8,232 first-time consultations of adults were identified who had sought medical care at the facility during a 12-year span between January 1, 2007, and December 31, 2019. We excluded 1,741 cases, who did not meet our inclusion criteria. The inclusion criteria were (1) completion of self-report questionnaires at first-time visits covering demographic data, somatic symptomatology, and a mental health assessment, and (2) provision of written informed consent. Ultimately, 6,491 participants were included in our study because of the completeness of the assessment instruments.

Sociodemographic variables were compared to the German population census, a national survey conducted annually to gather demographic, social, and economic data on the country’s residents by the governmental authority of the German Federal Statistical Office. The extent of mental symptom load in our study sample was compared to that in a large clinical sample of psychosomatic outpatients (n = 2,987) using the ICD-10-ISR by Timmermann [19].

Demographic data such as age, gender, source of income, and level of education were collected by the interviewing physician. At the initial appointment, the patients underwent computer-based psychometric testing before visiting the doctor. Patients who did not feel comfortable using a computer performed the pen-and-paper versions of the psychometric tests. The questionnaires used to assess somatic symptomatology and psychobehavioral factors in the study were the “Hamburger Modules for Measuring Generic Aspects of Psychosocial Health in the Therapeutic Practice” (HEALTH-49 [H49]) and the ICD-10-Symptom-Rating (ISR).

The H49 measures different aspects of psychosocial health to inform diagnostics and therapeutic planning. The instrument has proven to be valid, comprehensive, and economical in previous studies, particularly in German-speaking countries [20‒22]. It includes 49 items assessing various domains such as psychological complaints, coping, life satisfaction, and experience with social networks. Rating was assigned using a Likert scale ranging from 0 (indicating no presence) to 4 (indicating an intense presence). Thus, higher scores indicated a higher degree of concern. The 9 subscales employed are “Somatic symptom reporting” (H49-SOM), “Depression” (H49-DEP), “Phobic Anxiety” (H49-PHO), “Psychological well-being” (H49-WELL), “Interactional difficulties” (H49-INT), “Self-efficacy” (H49-SELF), “Activity and Participation” (H49-AP), and “Social support” (H49-SOS) and “Social burden” (H49-SOB).

The H49-SOM subscale consists of seven items that specifically assess somatic symptoms that are often present in somatoform disorders. These include back pain, digestive problems, numbness and tingling in various body parts, feelings of heaviness or weakness in the limbs, facial or headache pain, and pain in muscles or joints. For example, the related item reads “How much have you suffered from pain in your muscles or joints in the last 2 weeks?”. Cronbach’s alpha for the H49 sum score was α = 0.83, with subscales: H49-SOM α = 0.83, H49-DEP α = 0.85, H49-PHO α = 0.88, H49-INT α = 0.83, H49-SELF α = 0.86, H49-AUP α = 0.77, H49-SOB α = 0.67, H49-SOS α = 0.82, and H49-WELL α = 0.77.

The ISR is a self-assessment questionnaire that measures 5 syndrome scales as well as 12 additional items [19]. Syndromes that are commonly associated with various disorders, such as anxiety or depression, have been assessed [23]. The ISR consists of 29 items, each rated on a five-point Likert scale ranging from 0 (“not present”) to 4 (indicating “very severe” symptoms). The ISR total score may range from 0 to 4 and is obtained by the mean of the five subscales and double-weighted additional items. The five domains covered by the ISR are somatoform disorders (ISR-SOM), anxiety and phobic disorders (ISR-PHO), depressive disorders (ISR-DEP), obsessive-compulsive disorders (ISR-OCD) and eating disorders (ISR-EAT) [24].

The reliability of the item statistics was supported by item-total correlations. Cronbach’s alpha for the ICD-10-ISR sum score was α = 0.90, with the subscales ISR-SOM α = 0.82, ISR-PHO α = 0.85, ISR-DEP α = 0.80, ISR-OCD α = 0.78, and ISR-EAT α = 0.81.

The ISR-SOM encompasses a triad of items that gauge excessive health concern. These are “I have the need to go to the doctor because of unexplained physical complaints.”, “I suffer from the constant nagging worry of being physically ill.” and “Various doctors assure me that I do not have any physical illness, but I find it difficult to believe them.”

This measure was intended to assess the extent to which the experience of somatic complaints is excessively distressing and disruptive to an individual. Thus, the ISR-SOM scale covers the core construct of the current B-criteria for SSD.

To check for data validity, correlation analysis of H49-PHO and ISR-PHO, as well as H49-DEP and ISR-DEP, was carried out. There was a strong correlation between the corresponding subscales for depression (Pearson’s r = 0.76) and anxiety (Pearson’s r = 0.61) between the H49 and ICD-10-ISR subscales.

Two regression models were constructed using the inclusion approach. The H49-SOM was used as the dependent outcome variable, representing somatic symptom reporting (A-criteria). As independent variables in the first model, ISR-SOM representing the SSD B-criteria and the remaining subscales of the H49 and ISR scales, representing different psychobehavioral factors were incorporated. The second model included a range of sociodemographic variables.

The statistical significance of the coefficients was determined using Student’s t test. The results were considered significant at α = 5% and were corrected using the Bonferroni method for multiple testing models. Both models included 35 observations, resulting in a threshold applied for significance of p < 0.0014. Missing data were not addressed, as completeness of the data was an inclusion criterion. The anonymized data sample was analyzed using SPSS Statistics for Windows, Version 28.0 (IBM SPSS Statistics for Windows, Version 28.0. Armonk, NY, USA: IBM Corp).

The sociodemographic characteristics of the participants are outlined in Table 1. Compared with the German population census [25], patients in our clinical sample were more often female (62.4% vs. 51.0%), lived in a partnership (53.5 vs. 43.0%), did not have German citizenship (15.4% vs. 12.5%), and were younger age (38.4 vs. 44.5 years). The rate of 35.7% of participants receiving unemployment benefits is rather high compared to other samples of psychosomatic outpatients in Berlin (14%; [26]) and psychosomatic inpatients all over Germany (19.6%; [27]).

We observed a high overall mental symptom load in our patient sample. Compared to the sample by Timmermann, all subscales and the sum score of the ISR indicated a significantly higher symptom load [19]. The sum score was 1.59 (SD 0.64) in our sample compared to 1.29 (SD 0.7), which was significant at p < 0.001 (DF = 9,476, t = 19.877).

The established B-criteria for SSD were moderately associated with somatic symptom reporting in our sample. Standardized beta (β) was β = 0.34 (R² = 0.371, df = 11, F = 346.811) in the multiple regression analysis of psychobehavioral factors (Model 1; see Table 2). It remained nearly unchanged with β = 0.31 (R² = 0.428, df = 24, F = 187.886) when adjusting for possible confounders (Model 2). By squaring this β, we could determine that the B-criteria alone explained 9.6% of the variance in somatic symptom reporting in the confounder-adjusted model (Fig. 1).

Depression, as measured by the ISR, was also associated with somatic symptom reporting in both models, albeit to only half the extent of the B-criteria. With β = 0.15, they account for 2.3% of the explained variance in somatic symptom reporting. Impaired Activity and Participation (H49-AUP) was significantly and independently correlated with somatic symptom reporting in models 1 and 2 (β = 0.1; β = 0.12, explained variance of 1 resp. 1.4%). Subscales of Anxiety and Interactional difficulties showed values of β = 0.1 in model 1, but the explained variance in adjusted model 2 was below 1%.

Adjusting for possible sociodemographic confounders results in an increase in explained total variance from R² = 0.37 (model 1) to R² = 0.43 (model 2). Higher age and female gender were independently associated with somatic symptom reporting (β = 0.16, resp. β = 0.12), accounting for explained variances of 2.6% and 1.4%. The mode of household income, school education, partnership, and application for a reduced-earning capacity pension each explained less than 1% of the variance. All independent variables that accounted for at least 1% of the variation in reporting somatic symptoms (β ≥ 0.1) were highly significant in both regression models, as evidenced by p values <0.001 (Fig. 1).

We investigate the association of established B-criteria and other psychobehavioral factors with somatic symptom reporting. Regression analysis revealed that the B-criteria were the strongest independent variables associated with somatic symptom reporting. This finding is consistent with the concept of SSD, which emphasizes the importance of the specific psychological symptomatology associated with the extent of somatic symptom reporting [3].

The inclusion of other psychobehavioral factors in the regression model allowed for a comprehensive evaluation of their association with somatic symptom reporting in this setting (Table 2; Fig. 1). There is extensive evidence in the literature that acknowledges the connection between somatic symptom reporting and depression and anxiety [1, 28, 29]. A review of longitudinal studies that examined predictors of somatic symptom onset also identified anxiety and depression, as well as sleep problems and fatigue, as psychological factors with a strong level of evidence [30]. Studies have demonstrated that there are significant overlaps between these syndromes, with a correlation observed between the number of symptoms reported in somatoform symptoms and levels of depressive or anxious states [1, 4, 31].

Our study allows for a direct comparison of the association of the B-criteria, as well as depression and anxiety, with somatic symptom reporting. This finding supports the thesis of a relevant and distinct psychological construct of excessive health concerns related to higher somatic symptom reporting, as these concerns determine a substantially greater part of the variance than depression and anxiety.

Impaired Activity and Participation may reflect avoidance behavior associated with somatic symptom reporting, as reported in earlier studies [16, 32]. Interestingly, these factors, as well as interactional difficulties, explained only approximately 1% of the variance in symptom reporting in model 1 and slightly less in model 2 (β = 0.09). The H49-INT items ask for difficulties in emotional awareness and communication [22]. Related research on impaired reflexive functioning – a construct derived from the theory of mentalization as well as insecure or disorganized attachment styles in children – has pointed toward a relationship with a diagnosis of SSD [33, 34]. Our results suggest a weak association of these psychological factors in empirically determining their direct relationship with symptom reporting. It might be interesting to further elucidate these factors by adding additional measures to self-reported disturbances.

Deficient social support also had a surprisingly low impact on symptom reporting in our model. This finding does not correspond to the findings of other studies that have attributed the lack of social support to a higher impact on symptom load in SSD or somatoform symptoms [14, 35]. One reason for this could be the use of different testing measures in our approach. This outcome may be partially attributed to the characteristics of our patient sample. Our study specifically focused on individuals who actively sought assistance from a psychosomatic outpatient department, where appointments were scheduled only through direct personal interaction with the institution. This distinction could potentially act as a moderating factor when comparing our findings to those of population-based studies. The ability and will to search for advice and help when suffering from somatic symptoms might be a reflection of a patient group willing to gain help from a specialized treatment center and does not lack as much social support as other subgroups do. Further studies with different patient groups may shed more light on this issue.

Our findings indicate that being female and older independently increases the likelihood of reporting somatic symptoms. This observation aligns with previous research on the association between female gender as well as older age on a heightened prevalence of somatic symptomatology [14, 15]. In a representative sample of the German population, the authors identified a mean age of 56.1 years and 67.6% of the sample to be female, indicating that both characteristics are more pronounced than in the general population [36]. This is contradictory to a Chinese study of 699 general hospital outpatients, where no gender differences were found in SSD-patients [37].

Other potential psychosocial variables accounted for less than 1% of the observed variance. These variables included having a lower level of education, being in a committed relationship, and receiving financial support from government authorities or public health insurance. It is evident that these factors still exert an association with symptom reporting, albeit to a much lesser extent than the established B criteria and other factors previously described.

This study was retrospective and cross-sectional. This design limits the ability to establish causality between symptom reporting and possibly related psychobehavioral factors, as have been examined previously [30, 38, 39].

In our study, we were unable to determine the number or severity of medical illnesses, which made it impossible for us to control for any confounding somatic comorbidities that might have influenced the reporting of somatic symptoms. In another study, the number of medical illnesses at the start of the study was found to be a significant predictor of somatic symptom reporting at a later follow-up [40]. However, it is worth noting that all of the patients in our study were recruited from a psychosomatic outpatient center. Typically, a thorough investigation of somatic symptoms is conducted prior to referral to the center, which is based on the finding, that symptoms are not fully explained by underlying disease pathology.

This study relied on self-report questionnaires to assess somatic symptoms and mental health. The ISR-SOM used was not originally intended to capture the currently established B-criteria, which might lead to miscapturing aspects of excessive thoughts, behaviors, and emotions compared to a specific questionnaire such as the SSD-12 [12]. H49-SOM is relatively brief compared with other available checklists for somatic symptoms.

Although self-report measures are commonly used in clinical practice and research, they are subject to social desirability and recall biases. Future studies are needed to add additional-specific measures or clinician-rated assessments as well as longitudinal data to complement self-report data and provide a more comprehensive assessment of SSD symptoms.

This study offers valuable insights into the usefulness of the B-criteria for identifying SSD in clinical practice. The study confirms the relationship between the B-criteria and somatic symptom reporting in a clinical setting, demonstrating the importance of these criteria in the diagnosis of SSD. This is especially relevant given the complexity of diagnosing SSD in the presence of other medical conditions.

Beyond established B-criteria we explore the importance of additional psychobehavioral factors for somatic symptom reporting. We report the weighted contribution of known psychological factors such as depression and demographic factors such as age and female gender. This highlights the multifactorial nature of SSD and suggests that a comprehensive approach, considering both the B-criteria and other psychobehavioral factors, may be necessary for further validation and treatment of SSD, as has been stimulated by recent research, e.g., from the EURONET-SOMA group [41, 42].

This study’s outcomes have significant ramifications for future research on individuals with SSD. To confirm a strong connection between the B-criteria and somatic symptom reporting, it is crucial to conduct longitudinal studies. Clinicians may then focus on addressing these excessive health concerns and behaviors as well as other psychobehavioral factors during their diagnostic evaluations and therapeutic interventions.

Furthermore, by examining other psychobehavioral factors in such studies, treatment plans can be customized to meet the unique requirements of patient groups, taking into account the diversity in symptomatology and the underlying mechanisms. To better understand the role of specific psychobehavioral factors in SSD, future research should incorporate longitudinal data and employ multi-method approaches.

The authors wish to thank Dr. Michael Rudolph, former Head of the Institute of Psychosomatic Medicine, Centrum fuer Gesundheit AOK Nordost, for supporting the analysis.

The study protocol was reviewed and approved by the Ethics Committee of the Berlin Medical Association (approval number: Eth 32/21). The patients provided written informed consent to participate in this study, and all investigations in the present study were conducted in accordance with the Declaration of Helsinki.

M.H. received book royalties (Hogrefe) and speaker fees. S.P. received book royalties (Springer Nature) and speaker’s fees. R.M. received book royalties (Pabst, Hippocampus) and speaker fees. M.R. received book royalties and speaker fees.

The authors did not receive financial support from any organization for the submitted work.

M.H. conceived and designed the analysis, collected the data, performed the analysis, and wrote the paper. S.P., R.M., and M.R. contributed to the interpretation of the analysis and reviewed the manuscript.

The data in this study were obtained from the psychosomatic outpatient center as a third-party institution. Further access to the dataset may be requested from the M.H.