Validation of the German version of the Bodily Distress Syndrome 25 checklist in a representative German population sample

Hair cortisol and self-perceived stress in adolescents with multi-system functional somatic disorders

BACKGROUND

Long-term stress causing altered hypothalamic-pituitary-adrenal (HPA) axis dynamics with cortisol dysfunction may be involved in the pathophysiology of functional somatic disorders (FSD), but studies on adolescents with multi-system FSD are lacking. Therefore, we investigated: 1) whether hair cortisol concentration (HCC) differentiates adolescents with multi-system FSD from a) a population-based sample and b) a subgroup derived from the sample reporting a high physical symptom load, and 2) whether FSD population HCC is associated with primary symptom presentations and self-perceived stress.

METHODS

We used data from a clinical sample with multi-system FSD (N = 91, age 15-19 years) and a population-based sample (N = 1,450, age 16-17 years) including a subgroup with top 10% total scores on physical symptoms (N = 147). Density plots and multiple linear regression were applied to compare HCC between groups. In the clinical sample, multiple linear regression was employed to assess the association between HCC and primary symptom clusters and self-perceived stress.

RESULTS

Median HCC was lower in the clinical sample than in the population-based sample (β = 0.80 (95%CI: 0.66, 0.97)), but not significantly different from median HCC in the derived subgroup (β = 0.84 (95%CI: 0.66, 1.07)). In the clinical sample, HCC was not significantly associated with primary symptom clusters (F(2, 82) = 0.13, p = 0.88) or self-perceived stress (F(4, 83) = 1.18, p = 0.33).

CONCLUSION

Our findings indicate that HCC is lowered in adolescents with multi-system FSD but not significantly associated with primary symptom presentations or self-perceived stress. Future studies including multiple measures of HPA axis dynamics alongside psychological measures may further elucidate the role of long-term stress in FSD.

TRIAL REGISTRATION

The AHEAD study was pre-registered at ClinicalTrials.gov (NCT02346071), 26/01/2015.

Validation of the irritation scale on a representative German sample: new normative data

The irritation scale is a widely used and reliable self-report scale for measuring cognitive and emotional strain related to the work environment. It extends existing measures by providing a sensitive assessment for pre-clinical stress at work. Existing normative data are based on convenience samples and are therefore not representative. This study provides new normative data for the irritation scale based on a representative German sample (N = 1480). The new normative data indicate that the overall level of irritation in the German workforce is significantly lower compared to previously published data. Convergent and discriminant validity is confirmed by correlations with depression and anxiety (Patient Health Questionnaire-4 for Depression and Anxiety), somatic symptom scales (Bodily Distress Syndrome 25 checklist, Somatic Symptom Scale-8, Giessen Subjective Complaints List-8, comorbidity), psychological functioning (Mini-ICF rating for activity and participation disorders in mental illness), work-related stressors (overcommitment and bullying) and individual resources (self-efficacy). The results confirm the utility of the irritation scale and provide new benchmarks that avoid an underestimation of the levels of irritation in future studies.

Functional Somatic Disorders, Their Subtypes, and Their Association With Self-Rated Health in the German General Population

OBJECTIVE

The heterogeneous conceptualizations and classifications of persistent and troublesome physical symptoms impede their adequate clinical management. Functional somatic disorder (FSD) is a recently suggested interface concept that is etiologically neutral and allows for dysfunctional psychobehavioral characteristics as well as somatic comorbidity. However, its prevalence and impact are not yet known.

METHODS

We analyzed 2379 participants (mean age = 48.3 years, 52.5% female) from a representative German community survey using operationalized FSD criteria. These criteria defined FSD types based on somatic symptom count, type, and severity assessed by the Bodily Distress Syndrome Checklist. In addition, the associations of those types with health concerns, comorbidity, psychological distress, and self-rated health were determined.

RESULTS

There were four clearly demarcated groups with no relevant bothering symptoms, with one or with few bothering symptoms from one organ system, and with multiple bothering symptoms from at least two organ systems. Psychological distress, health concerns, and comorbidity steadily increased, and self-rated health decreased according to the number and severity of symptoms. Somatic symptom burden, health concerns, and comorbidity independently predicted self-rated health, with no interaction effect between the latter two.

CONCLUSIONS

Our data support an FSD concept with two severity grades according to persistent and troublesome symptoms in one versus more organ systems. The delimitation of subtypes with psychobehavioral characteristics and/or with somatic comorbidity seems useful, while still allowing the demarcation of a group of participants with high symptom burden but without those additional characteristics.

High Perceived Stress and Low Self-Efficacy are Associated with Functional Somatic Disorders: The DanFunD Study

Objective

Several psychological factors have been proposed to be associated with functional somatic disorders (FSD) including functional somatic syndromes, such as irritable bowel, chronic widespread pain, and chronic fatigue. However, large randomly selected population-based studies of this association are sparse. This study aimed to investigate the association between FSD and perceived stress and self-efficacy, respectively, and to investigate if FSD differed from severe physical diseases on these aspects.

Methods

This cross-sectional study included a random sample of the adult Danish population (n = 9656). FSD were established using self-reported questionnaires and diagnostic interviews. Perceived stress was measured with Cohen's Perceived Stress Scale and self-efficacy with the General Self-Efficacy Scale. Data were analysed with generalized linear models and linear regression models.

Results

FSD were associated with higher perceived stress and lower self-efficacy, especially for the multi-organ and the general symptoms/fatigue FSD types and for chronic fatigue. However, controlling for the personality trait neuroticism altered the associations with self-efficacy so it became insignificant. The analysis did not support an important interaction between perceived stress and self-efficacy on the likelihood of having FSD. Individuals with FSD presented levels of perceived stress that were not equal, ie higher, to those in individuals with severe physical diseases.

Conclusion

FSD were positively associated with perceived stress and negatively associated with self-efficacy. Our study may point to stress being part of the symptomatology of FSD. This underlines the severity of having FSD and stresses the relevance of the resilience theory in the understanding of the condition.

Coping strategies among individuals with multiple physical symptoms: A general population-based cross-sectional study

OBJECTIVE

Coping has been suggested as a perpetuating factor for physical symptoms. The aim of this study was to examine the use of the coping strategies approach, resignation, and diversion in individuals with multiple physical symptoms according to the construct of Bodily Distress Syndrome (BDS).

METHODS

This cross-sectional study was part of the nationwide web-based survey Danish Symptom Cohort (DaSC). In total, 100,000 individuals were invited to participate, and individuals eligible for the present study were respondents aged 20-64 years without a current or recent pregnancy. Multiple physical symptoms were identified using the BDS checklist, and coping was assessed by the Brief Approach/Avoidance Coping Questionnaire. Statistical analyses included descriptive statistics and multinomial and logistic regression.

RESULTS

A total of 35,810 respondents were included in the study, of which 8512 (23.8%) fulfilled the criteria for having multiple physical symptoms. This group of respondents had lower coping scores on approach and higher coping scores on resignation and diversion compared with the non-BDS group. The regression analyses showed that high scores on approach were associated with a lower probability of having multiple symptoms (adjusted OR 0.92, 95% CI: 0.91-0.92), whereas high scores on diversion and resignation were associated with a higher probability of having multiple symptoms (adjusted OR 1.10; 95% CI: 1.09-1.11 and adjusted OR 1.19; 95% CI: 1.18-1.20, respectively).

CONCLUSION

The study supports the hypothesis that experiencing multiple physical symptoms is associated with certain coping strategies. This is relevant knowledge for health care professionals who will be treating this patient group.

Can the bodily distress syndrome (BDS) concept be used to assess functional somatic symptoms in adolescence?

OBJECTIVE

Bodily Distress Syndrome (BDS) represents a new research concept for adult patients with various functional somatic syndromes. We evaluated the utility of the BDS research concept and the associated BDS-25-checklist as a screening tool for diverse functional somatic symptoms (FSS) in adolescence by investigating: 1) the psychometric and factorial structures of the checklist, 2) symptom cluster patterns and 3) illness classification and associations with emotional psychopathology and sociodemographic factors.

METHODS

This cross-sectional study obtained data from the 16/17-year follow-up (N = 2542) of the general population Copenhagen Child Cohort 2000 (CCC2000). We used self-reported questionnaires to assess physical symptoms (the BDS-25 checklist), overall health (KidScreen), emotional psychopathology (Spence Children's Anxiety Scale; The Mood and Feelings Questionnaire), and illness worry (Whiteley-6 Index), and utilized data from Danish national registers to assess sociodemographic factors.

RESULTS

The BDS-25 checklist items displayed satisfactory psychometric data quality. Factor analyses revealed a similar four-factor model as reported in adults (factor loadings λ ≥0.5), representing distinct BDS symptom clusters: cardio-pulmonary, gastro-intestinal, musculoskeletal and general symptoms. Latent class analyses revealed a model with three latent classes, i.e. probable no to mild BDS, probable moderate, single-organ BDS and probable severe, multi-organ BDS, displaying acceptable class quality (Entropy = 0.904). Trend analyses revealed sociodemographic group differences across latent classes. Increased emotional psychopathology was associated with more pronounced BDS symptoms.

CONCLUSION

Our findings support the BDS concept with four symptom clusters and three illness severity groups (no BDS, single- organ and multi-organ BDS) to screen for FSS in adolescence.

A multicenter study of bodily distress syndrome in Chinese outpatient hospital care: prevalence and associations with psychosocial variables

BACKGROUND

Bodily distress syndrome (BDS) is a new, empirical-based diagnosis of functional somatic symptoms. This study aimed to explore the prevalence of BDS and its association with psychosocial variables in a Chinese clinical population.

METHODS

A multicentre cross-sectional study of 1269 patients was conducted in 9 different Chinese tertiary outpatient hospitals. The BDS was identified by trained interviewers face-to face, based on a brief version of the Schedules for Assessment in Neuropsychiatry (RIFD) and the BDS Checklist-25. Sociodemographic data and further information were characterised from psychometric questionnaires (The Patient Health Questionnaire-15, the Patient Health Questionnaire-9, the General Anxiety Disorder-7, the Whiteley scale-8) .

RESULTS

Complete data were available for 697 patients. The prevalence of BDS was 26.8% (95% confidence interval (CI): 23.5-30.1). Among the participants, 5.8% (95% CI: 4.1-7.6) fulfilled the criteria for single-organ BDS, while 20.9% (95%CI: 17.9-24.0) had multi-organ BDS. Comparison of the PHQ-15, PHQ-9, GAD-7, and WI-8 scores revealed higher scores on all dimensions for patients with BDS. In a binary logistic regression analysis, BDS was significantly associated with increased health-related anxiety (WI-8) and depression (PHQ-9). The explained variance was Nagelkerke's R² = 0.42.

CONCLUSIONS

In China, the BDS is a common clinical condition in tertiary outpatient hospital settings with high prevalence, and is associated with health anxiety and depressive symptoms. In this clinical population, the severe multi-organ subtype of BDS was the most frequent.

Neuroticism and adverse life events are important determinants in functional somatic disorders: the DanFunD study

Several psychological factors have been proposed to be associated with functional somatic disorders (FSD). However, large population-based studies investigating the importance of both personality and adverse life events (ALE) are sparse. This study aimed to investigate the association between FSD and neuroticism and the accumulated number of ALE, respectively. This cross-sectional study included a random sample of the adult Danish population (N = 7493). FSD were established by means of self-reported questionnaires and diagnostic interviews. Neuroticism was measured with the Danish version of the short-form NEO Personality Inventory. ALE were measured with the Danish version of the Cumulative Lifetime Adversity Measure. Strong positive associations were found between neuroticism and FSD, and ALE and questionnaire-based FSD. For interview-based FSD, strong positive associations were found for FSD, multi-organ type, and for the subtype of the general symptoms. The level of self-efficacy did not modify these associations, and no moderating effect of neuroticism and ALE in combination on the probability of having FSD was found. FSD were strongly associated with both neuroticism and the accumulated number of ALE, and these associations were not modified by self-efficacy. In combination, neuroticism and ALE did not have a moderating effect on the probability of having FSD.

The risk factors for self-reported fibromyalgia with and without multiple somatic symptoms: The Lifelines cohort study

OBJECTIVE

The numerous risk factors for fibromyalgia reflect its heterogeneous nature. This study assessed whether the predictors of fibromyalgia onset vary according to number of prior somatic symptoms.

METHODS

The prospective, population-based Lifelines cohort study included 138,617 adults without fibromyalgia or marked muscle pain. At baseline socio-demographic status, physical and psychiatric disorders, psycho-social and behavioural variables were assessed as potential predictors. At follow-up (mean 2.4 years later) new onsets of fibromyalgia were recorded by self-report. The predictors of new onsets of self-reported fibromyalgia were assessed using logistic regression with interaction terms between key variables and number of somatic symptoms.

RESULTS

At follow-up 679 (0.5%) participants reported new onset fibromyalgia. The strongest predictors were: female sex, rheumatoid and osteo-arthritis, IBS, impaired sleep, migraine, few years of education and impairment by bodily pain. Interaction terms with somatic symptoms were significant for years of education, low income, rheumatoid arthritis and no. of analgesics; these were predictors only for fibromyalgia with few somatic symptoms. Participants with multiple somatic symptoms had a higher number of predictors than those with few somatic symptoms.

CONCLUSION

This study suggests that people developing self-reported fibromyalgia with multiple pre-existing somatic symptoms have a high risk factor load reflecting risk factors for both fibromyalgia and multiple somatic symptoms. Self-reported fibromyalgia with few somatic symptoms has fewer predictors which may be specific to fibromyalgia. Future research could usefully study whether different pathophysiological mechanisms occur when fibromyalgia is preceded by high or low number of somatic symptoms.

Validity and utility of Hierarchical Taxonomy of Psychopathology (HiTOP): III. Emotional dysfunction superspectrum

The Hierarchical Taxonomy of Psychopathology (HiTOP) is a quantitative nosological system that addresses shortcomings of traditional mental disorder diagnoses, including arbitrary boundaries between psychopathology and normality, frequent disorder co-occurrence, substantial heterogeneity within disorders, and diagnostic unreliability over time and across clinicians. This paper reviews evidence on the validity and utility of the internalizing and somatoform spectra of HiTOP, which together provide support for an emotional dysfunction superspectrum. These spectra are composed of homogeneous symptom and maladaptive trait dimensions currently subsumed within multiple diagnostic classes, including depressive, anxiety, trauma-related, eating, bipolar, and somatic symptom disorders, as well as sexual dysfunction and aspects of personality disorders. Dimensions falling within the emotional dysfunction superspectrum are broadly linked to individual differences in negative affect/neuroticism. Extensive evidence establishes that dimensions falling within the superspectrum share genetic diatheses, environmental risk factors, cognitive and affective difficulties, neural substrates and biomarkers, childhood temperamental antecedents, and treatment response. The structure of these validators mirrors the quantitative structure of the superspectrum, with some correlates more specific to internalizing or somatoform conditions, and others common to both, thereby underlining the hierarchical structure of the domain. Compared to traditional diagnoses, the internalizing and somatoform spectra demonstrated substantially improved utility: greater reliability, larger explanatory and predictive power, and greater clinical applicability. Validated measures are currently available to implement the HiTOP system in practice, which can make diagnostic classification more useful, both in research and in the clinic.

Validation of the Chinese version bodily distress syndrome checklist in Chinese out-patients of general hospitals

OBJECTIVE

The 25-item Bodily Distress Syndromes (BDS) checklist was developed to assess BDS symptoms with high validity and reliability. The aim of this study was to reveal the psychometric properties of the Chinese version of the BDS checklist in Chinese outpatients of general hospitals.

METHOD

A cross-sectional study was carried out in nine Chinese general hospitals, consisting of three different medicine settings: biomedicine, traditional medicine, and psychosomatic medicine. The 25-item BDS checklist was translated into the Chinese version and conducted on outpatients from all nine centers. We performed validity and reliability analyses, including test-retest reliability, construct validity, and internal consistency reliability, on the collected checklist data. The convergent validity of the BDS checklist was analyzed with Pearson's Coefficient vs. Patient Health Questionnaire-15 (PHQ-15). The discriminant validity of the BDS checklist was analyzed with Pearson's Coefficient vs. Patient Health Questionnaire-9 (PHQ-9), General Anxiety Disorder-7 (GAD-7) and Whiteley-8 (WI-8).

RESULTS

A total of 699 patients were included in this study. The test-retest reliability, construct validity, and internal consistency reliability of the Chinese version of the BDS were satisfactory in our study. Factor analyses identified five distinct determining factors: cardiopulmonary, gastric, intestinal, musculoskeletal, and general symptoms. Pearson's coefficients were found to be high in both discriminant validity and convergent validity analyses.

CONCLUSION

The results provide empirical support for the Chinese version of the BDS checklist in patients in general hospitals. The Chinese version of the BDS checklist is potentially valuable for case finding in both clinical practice and research in Chinese.

Assessment of functional somatic disorders in epidemiological research: Self-report questionnaires versus diagnostic interviews

OBJECTIVE

Self-reported symptom questionnaires are often used for identifying individuals with functional somatic disorders (FSD) in epidemiological research. Studies on their validity in establishing clinically valid cases are, however, lacking. We aimed to compare and dissect the processes of identifying participants with FSD with symptom questionnaires and FSD diagnoses established by diagnostic interviews.

METHODS

Individuals from the adult Danish population (n = 1590) filled in symptom questionnaires and participated in a diagnostic research interview, performed over telephone by trained family physicians. The two methods were described and compared in different steps: 1) Agreement on presence of symptoms, 2) agreement after FSD symptom pattern criteria had been applied, and 3) agreement on final FSD diagnoses.

RESULTS

Agreement on symptom presence was high (>82%). Using FSD symptom pattern criteria, the two methods agreed in 30-62% of cases within each category. Discrepancies were mainly due to participants fulfilling symptom patterns in the interview but not in the questionnaires. Agreement between final FSD questionnaire cases and final FSD interview diagnoses was moderate (>68%) with lower FSD prevalence in the interview (26.2% vs 44.5%). Discrepancies were largely explained by the interviewers assessing the symptom patterns to be caused by an alternative physical or mental condition.

CONCLUSION

Prevalence of final FSD diagnoses were markedly lower in the diagnostic interview compared to self-reported questionnaires cases; mainly because of the clinical evaluation of symptom attribution and impairment. Symptom questionnaires may be valuable as screening tools and as trans-diagnostic comparison while diagnostic interviews are necessary in establishing clinically significant FSD diagnoses.

Three different approaches to delimitation of functional somatic disorders: DanFunD

OBJECTIVE

The Danish Study of Functional Disorders (DanFunD) approaches functional somatic disorders (FSD) with three delimitations: Five functional somatic syndromes (FSS), Bodily Distress Syndrome (BDS), and eight data-driven symptom profiles (SP). This paper presents each delimitation and discusses optimal approaches for further original research into FSD epidemiology.

METHODS

A total of 9656 adults from the general Danish population participated in this cross-sectional study. Case assignment of the three FSD delimitations was based on self-reported symptom questionnaires. Overlap of FSS, BDS, and SP and their association with poor self-perceived health were calculated as descriptive statistics and shown with Venn diagrams. Difference in self-perceived health between participants with severe FSD were compared with participants with no FSD and calculated as risk ratios with generalized linear models with binomial family and log link.

RESULTS

We found pronounced overlaps between any FSS, BDS, and the SP with multiple symptoms as well as for multi-organ BDS and the SP with all symptoms. Symptoms and syndromes related to clusters of musculoskeletal and general symptoms contributed particularly to poor health as did multi-organ BDS and categories of SP with multiple symptoms.

CONCLUSION

Each of the three delimitations has its strengths and weaknesses, and with this study, we offer a contribution to a more valid delimitation of FSD. Future research within DanFunD and other epidemiological studies may benefit from using more than just one delimitation for capturing the diverse nature of the FSD.

The BDS checklist as measure of illness severity: a cross-sectional cohort study in the Danish general population, primary care and specialised setting

OBJECTIVE

The bodily distress syndrome (BDS) checklist has proven to be useful in the diagnostic categorisation and as screening tool for functional somatic disorders (FSD). This study aims to investigate whether the BDS checklist total sum score (0-100) can be used as a measure of physical symptom burden and FSD illness severity.

DESIGN

Cross-sectional.

SETTING

Danish general population, primary care and specialised clinical setting.

PARTICIPANTS

A general population cohort (n=9656), a primary care cohort (n=2480) and a cohort of patients with multiorgan BDS from specialised clinical setting (n=492).

OUTCOME MEASURES

All data were self-reported. Physical symptoms were measured with the 25-item BDS checklist. Overall self-perceived health was measured with one item from the 36-item Short-Form Health Survey (SF-36). Physical functioning was measured with an aggregate score of four items from the SF-36/SF-12 scales 'physical functioning', 'bodily pain' and 'vitality'. Emotional distress was measured with the mental distress subscale (SCL-8) from the Danish version of the Hopkins Symptom Checklist-90. Illness worry was measured with the six-item Whiteley Index.

RESULTS

For all cohorts, bifactor models established that despite some multidimensionality the total sum score of the BDS checklist adequately reflected physical symptom burden and illness severity. The BDS checklist had acceptable convergent validity with measures of overall health (r=0.25-0.58), physical functioning (r=0.22-0.58), emotional distress (r=0.47-0.62) and illness worry (r=0.36-0.55). Acceptability was good with a low number of missing responses to items (<3%). Internal consistency was high (α ≥0.879). BDS score means varied and reflected symptom burden across cohorts (13.03-46.15). We provide normative data for the Danish general population.

CONCLUSIONS

The BDS checklist total sum score can be used as a measure of symptom burden and FSD illness severity across settings. These findings establish the usefulness of the BDS checklist in clinics and in research, both as a diagnostic screening tool and as an instrument to assess illness severity.

Feasibility of group-based acceptance and commitment therapy for adolescents (AHEAD) with multiple functional somatic syndromes: a pilot study

BACKGROUND

Recurrent and impairing functional somatic syndromes (FSS) are common in adolescents. Despite a high need for care, empirically supported treatments are lacking for youth. The aim of this uncontrolled pilot study was to assess feasibility and treatment potential of a new intervention with group-based Acceptance and Commitment Therapy (ACT) in a generic treatment approach for adolescents with multiple FSS.

METHODS

Twenty-one patients received 'ACT for Health in Adolescents' (AHEAD) (30 h), specifically developed for adolescents (aged 15-19 years) with moderate to severe FSS. Close relatives attended an information meeting to facilitate support of the patients throughout treatment. Treatment satisfaction was evaluated by means of self-report and relatives' impressions. Self-reported physical health at 3 months follow-up (FU) after end of treatment was the primary outcome whereas secondary outcomes included symptom burden, limitation due to symptoms, illness worry, emotional distress and physical and emotional symptoms. Treatment targets were assessed by measures on illness behaviour, illness perception and psychological inflexibility.

RESULTS

Nineteen patients (90.5%) completed the treatment with a high overall attendance rate of 93%. All would recommend the treatment to a friend with similar problems. Close relatives rated it valuable to participate in an information meeting. Patients' physical health improved significantly from assessment to FU with a clinically relevant mean change of 8.9 points (95% CI [5.4; 12.4]; SRM 0.91 [0.26;1.57]). Improvement was also seen on all secondary outcome measures, from assessment to FU. Maladaptive illness behaviours and perceptions as well as psychological inflexibility showed a significant decline from assessment to FU.

CONCLUSION

AHEAD was feasible and potentially efficacious and warrants testing in a larger clinical trial.

TRIAL REGISTRATION

Clinical Trials gov NCT04464447 , registration date July 9th, 2020. Retrospectively registered.

Prevalence and overlap of somatic symptom disorder, bodily distress syndrome and fibromyalgia syndrome in the German general population: A cross sectional study

OBJECTIVE

To study the prevalence and clinical characteristics of Somatic Symptom Disorder (SSD), Bodily Distress Syndrome (BDS) and fibromyalgia syndrome (FMS) and their overlap in the general German population.

METHODS

A cross-sectional nationally representative population survey was performed. 2531 participants (mean age 48.8 ± 17.85 years, 53.3% women) completed the Somatic Symptom Scale SSS-8, the Bodily Distress Syndrome (BDS) 25 checklist, the Whiteley Index 7 (WI-7), the self-administered comorbidity questionnaire and the Michigan Body Map. Case definitions of SSD, BDS and FMS were assigned using established criteria.

RESULTS

4.5% of participants met the criteria of SSD (SSS - 8 at least one item "bothered very much" and WI- 7 total score ≥ 1). 9.6% met the criteria of single-organ BDS and 1.3% of multi-organ BDS. Prevalence of FMS according to 2016 criteria was 3.4%. 82.3% of FMS cases met any BDS criteria.28.1% of FMS cases satisfied SSD criteria. 28.8% of any BDS cases met the criteria of SSD. 75.1% of SSD cases met the criteria of any BDS. FMS cases reported the highest amount of somatic and psychological symptom burden and health anxieties. There were no differences in age and gender between any BDS and SSD cases. SSD cases reported worse general health and more fibromyalgia-related variables than any BDS cases.

CONCLUSIONS

In the general population, there is a substantial overlap between FMS and BDS, but not of FMS and SSD, and not of SSD and any BDS. Case definitions of the three disorders partially captured different groups in the general population.