To our knowledge, this is the first multicentre study with a large sample size conducted to investigate the prevalence and characteristics of the BDS in Chinese population. The present study revealed an overall BDS prevalence rate of 26.8% across all centres, while the prior studies have shown that the prevalence rate of the BDS ranges from 12–36%, with the single-organ subtype being more frequent [8, 26–28]. Notably, the results in our study revealed an opposite situation, that the multi-organ subtype of the BDS reported more frequent than the single-organ subtype. Several reasons may contribute to this difference. First, the samples collected in this study come from third-grade hospitals in China, where gathered patients who have a higher incidence of physical diseases than the general population and thus may have difficulty in getting diagnosed and treated in primary centres. The sample cluster may lead to a higher incidence. Second, previous studies have found that functional somatic disorders may be associated with cultural beliefs and social health education [29]. Chinese people are generally not good at expressing emotions. Instead, they tend to express their feelings indirectly by describing physical symptoms, which may account for the higher ratio of multi-organ subtypes [30].
Beutel et al. have reported that the majority age of BDS patients ranged from 41 to 65 years [31], which was consistent with our results (the BDS patients age was 42 ± 14.61). Additionally, PSY department reported higher BDS prevalence that in the TCM department. This might be explained by the fact that the patients with the BDS usually have unexplained somatic symptoms and are referred to the psychiatric departments by doctors from various departments. The significantly higher BDS-25 checklist total score in the PSY department could demonstrated the situation. What’s more, most patients who visited the TCM department reported mild symptoms, that may due to the nature of the department for TCM department is much more like a primary health centre that treat the normal physical distress.
There seems to be no significant difference in the gender composition between the groups. Same results have been found in the Danish study [31]. Nevertheless, recent studies have reported controversial results about the association between somatic symptom burden and sociodemographic factors. Beutel et al. has verified the association, including higher age, lower education, social and economic status, unemployment, and disruption of marriage relationship [32]. In the contrast, Cao et al. [33] showed that there were no differences in sociodemographic and lifestyle data between SSD and non-SSD patients. In accordance with the present study, no risk factors were found for ethnicity, living site, insurance, marital status, education, income, alcohol, occupation, or smoking status. The high rate of urban occupancy rate may result in this finding, for the low heterogeneity of the sample.
The multiple regression results shown that for every point increase in the WI-8, PHQ-9, and PHQ-15 scores, the risk of being diagnosed with BDS increases, which is consistent with previous studies [11, 14]. The results suggested that BDS patients suffered higher risk of depression and healthy anxiety compared to the control group, which is not surprised because depression and BDD are comorbid frequently, and there is a substantial overlap between depression and somatisation [14]. Furthermore, depression and somatisation may emerge from shared psychosocial and biological diatheses [14, 33]. Some studies have suggested that many of the phenomena of somatoform disorders are associated with low threshold clustering of psychiatric syndromes or their atypical manifestations [34].
4.1 Limitations
This study has several limitations. Because of the cross-sectional nature of our study, causality could not be inferred. It should be noted that the research approach used a Western biopsychosocial model of illness. Therefore, the possible culture-specific characteristics may not have been identified.
Another limitation of this study is that all included participants were restricted to three outpatient departments in China, which might result in a low heterogeneity.