Psychosocial Perspectives on Somatic Symptoms: Integrating Variable- and Person-Centered Approaches to Investigate Somatic Symptoms among Chinese Young Adults

Abstract

Somatic symptoms encompass subjective bodily discomforts, such as headaches and tiredness; these symptoms are a highly prevalent and significant burden among youth. Within this population, Chinese first-year university students who began their university education during the COVID-19 pandemic faced heightened vulnerability due to pandemic-related challenges associated with academic and social disruptions. Therefore, exploring the mechanisms underlying somatic symptoms is crucial for effectively managing and supporting this group. Theoretical advancements have shifted the understanding of somatic symptoms from a mind-body dualism towards a multidimensional framework that integrates biomedical, psychological, and social determinants. Grounded in this perspective, the biopsychosocial model serves as the dominant theoretical framework, and existing studies have identified a broad array of predictors for somatic symptoms at different levels (e.g., the HPA axis, anxiety, and social support).

However, there remain gaps in both theoretical frameworks and empirical investigations. Theoretically, the biopsychosocial model lacks clarity in specifying the levels of factors that should be prioritized and how multiple factors interact to influence somatic symptoms. Empirically, this theoretical ambiguity leads to an overemphasis on biomedical factors in practice, with psychosocial factors remaining underexplored. Among the existing research on psychosocial predictors, limitations include fragmented predictors, redundancy in unselected variables, and neglect of other essential psychosocial factors. Furthermore, insufficient longitudinal evidence has constrained examinations of the interplay between psychosocial predictors and somatic symptoms in direction. Importantly, most studies have adopted a variable-centered approach, which has assumed population homogeneity to examine the association between psychosocial predictors and somatic symptoms. However, treated as the outcome variable in these variable-centered studies, somatic symptoms themselves may exhibit distinct profiles with differing psychosocial predictors, which requires a person-centered approach to address these limitations by identifying symptom profiles. Theoretically, the profiles of somatic symptoms are still under a “lumpers-splitters” debate, which is concerned with whether symptoms reflect a single syndrome or distinct entities. Additionally, further exploration of the psychosocial predictors of different profiles may offer a nuanced understanding of their characteristics and underlying mechanisms.

Given the above knowledge gap, this thesis draws on the biopsychosocial model as the leading theoretical framework and combines both variable- and person-centered approaches to investigate the psychosocial mechanisms of somatic symptoms in Chinese young adults, in the context of the COVID-19 pandemic. As different timeframes can influence observed relationships, weekly assessments and day-to-day measurements should both be conducted for general patterns and daily experiences. More specifically, the thesis focuses on three research objectives: (a) identify key psychosocial predictors among predictor candidates and investigate their cross-sectional and longitudinal associations with somatic symptoms (Study 1); (b) examine the daily dynamics between key psychopathological factors and somatic symptoms (Study 2); and (c) explore the underlying profiles of somatic symptoms and their psychosocial predictors (Study 3).

Drawing on the biopsychosocial model, Study 1 selected key psychosocial predictors of somatic symptoms among a candidate pool generated from literature review. Advancing the biopsychosocial model by concretizing factor interactions as interconnected networks, Study 1 then utilized the network theory to explore how key predictors contribute to somatic symptoms both concurrently and over time. A total of 598 Chinese university students who enrolled in university education in Fall 2020 were recruited to complete a three-wave questionnaire survey voluntarily. Wave 1 (October 28 to November 14, 2020) measured demographics and candidate predictors with a pre-existing or a stable level, and Waves 2 and 3 (December 4 and 22, 2020, respectively) measured candidate predictors with potential fluctuations. The random forest analysis identified five key predictors with maximal contributions to somatic symptoms: anxiety symptoms, rumination, adverse life events, perceived stress, and daily hassles, while the pandemic background was examined but not selected as a key one. The network analysis showed that rumination played a central and bridging role in the contemporaneous network, alongside impacting and being impacted by others in the temporal network. Moreover, anxiety symptoms were positively associated with somatic symptoms in an undirected (cross-sectional) and directed (bidirectional prediction) way. These results highlighted rumination as the key node, and anxiety as the key edge in the psychopathological network of somatic symptoms.

Study 2 examined the day-to-day dynamics between somatic symptoms and rumination and anxiety, two of the key psychopathological factors identified by Study 1 that also serve as two critical psychosocial factors involved in perceptual-cognitive processes, based on the symptom perception model. Of the participants in Study 1, 582 participated in Study 2 to complete a seven-day daily diary via an online platform. In November 2020, participants reported their daily somatic symptoms, rumination, and anxiety by completing a diary questionnaire once per day before bedtime for seven consecutive days. The results of cross-lagged panel models identified reciprocal associations between daily rumination and daily somatic symptoms, as well as reciprocal associations between daily anxiety and daily somatic symptoms. Such bidirectional effects provided a more fine-grained picture of daily dynamics regarding symptom perception process with high ecological validity.

Studies 1 and 2 used a variable-centered approach to explore key psychosocial predictors and their associations with somatic symptoms from cross-sectional, longitudinal, and day-to-day perspectives, yet the symptoms per se may also present distinct clusters to affect the generalizability of these variable associations. Therefore, Study 3 adopted a person-centered approach to identify underlying symptom profiles and investigate how psychosocial predictors relate to such profiles. Based on the same data as Study 1, the cluster analysis identified three distinct symptom profiles: “high with gastrointestinal symptoms,” “moderate with tiredness,” and “low in all symptoms.” Greater rumination and anxiety characterized the first profile (the most at-risk one), as indicated by the classification and regression tree model. These findings offered insights into the commonalities and differences of somatic symptoms, revealing three symptom profiles characterized by shared symptoms of varying severity and distinct symptom patterns, which may involve different underlying psychopathological mechanisms. Notably, rumination and anxiety were prominent in the most at-risk profile, providing validity to the variable-centered results of Studies 1 and 2.

This thesis has theoretical implications. It substantiates and enhances the biopsychosocial model by elaborating on the specific roles of underexplored psychosocial predictors and integrating their interplay with somatic symptoms as an organic whole. The variable-centered findings identified the critical psychopathological factors associated with somatic symptoms, elucidated how these factors interact within the symptom network to contribute to somatic symptoms, and comprehensively examined the relationship between psychosocial predictors and somatic symptoms across multiple time frames, particularly showcasing the bidirectional associations between key predictors and somatic symptoms on a day-to-day basis. As these variable associations may differ across the symptom profiles, the person-centered results further advanced the theoretical understanding of symptom taxonomy by revealing symptom profiles, while the profile-specific characteristics also reinforced existing variable-centered findings.

More importantly, these findings have practical implications, especially for the current management of somatic symptoms and for building resilience against future crises. At the individual level, as cognitive-emotional factors outweighed the pandemic background, psychopathological network models offer a roadmap for early detection and tailored intervention with therapeutic targets, while diary-based symptom tracking enables timely and personalized interventions aligned with daily symptom fluctuations. On a broader scale, school and community could integrate psychoeducation on cognitive restructuring and affect regulation to equip young people with effective tools to better prevent and manage somatic symptoms. Healthcare providers should recognize and prioritize the somatic burden experienced by young people, investigate their unmet psychosocial needs, and ensure comprehensive follow-up care.

Date of Award	13 Aug 2025
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Xiaonan Nancy YU (Supervisor)