1. Introduction
Somatic symptom disorder is characterized by an extreme focus of a person on physical symptoms, such as pain, headaches, weakness, or shortness of breath, which causes significant distress and/or impairment in daily functioning [
1]. These symptoms are commonly observed among adolescents [
2,
3]; for example, a previous study found that the prevalence of somatic symptoms was 22.7% among 15–16-year-old adolescents in a cross-sectional study in Sweden [
4]. Although somatic symptoms are typically not life-threatening, they can affect individuals’ daily lives, such as sleep, psychological well-being, and social activities, which can reduce their quality of life and interfere with learning and work abilities. In addition, somatic symptoms often result in repeated and prolonged medical treatments, which can impose a significant economic burden on society [
5,
6].
The pathogenesis of somatic symptoms is unclear, i.e., medically unexplained symptoms (MUSs) [
7]. However, previous studies have suggested that negative life events may play a significant role in the development and course of somatic symptoms [
8]. Negative life events are often described as sudden and dramatic experiences, which have the potential to significantly alter an individual’s social world (e.g., unemployment, discrimination, or financial hardship) [
9,
10]. Proposed mechanisms for the association between negative life events and somatic symptoms involve physiological and emotional stress responses [
8]. These negative events often elicit unpleasant emotional experiences, such as unease, helplessness, negativity, anxiety, and so on, which can lead to the development of negative emotional states in individuals. For example, children or adolescents in their early stages of psychological development are particularly susceptible to the impact of negative life events and are at a higher risk of developing somatic symptoms [
11]. Additionally, previous research showed that the college students who have experienced high levels of childhood trauma reported more somatic symptoms, likely due to the stress associated with the transition period from adolescence to adulthood [
12]. In particular, the college students face a range of academic and social demands and need to adapt to various psychological changes in preparation for their working lives, which can make this period one of the most stressful periods of an individual’s life.
In addition to the impact of negative life events, research suggests that somatic symptoms are closely associated with depression [
13,
14]. A study found positive correlations between depression and somatic symptoms, including headache, stomach ache, constipation, diarrhea, backache, and fatigue [
14]. A cross-cultural study confirmed this link in both Japanese and American undergraduates, with significant correlations found between depression and somatic symptoms for both men and women [
15]. Notably, depression and depressive symptoms are prevalent among medical students, with a rate of 27.2% among 122,356 individuals across 43 countries [
16]. Studies have suggested that Chinese medical students with a mean prevalence of 32.74% in particular suffer from more severe depression [
17].
Negative life events can be significant stressors that contribute to the development of depressive symptoms in adolescents [
18]. Prolonged exposure to such events can lead to feelings of hopelessness and helplessness, which may, in turn, result in the development of depressive symptoms. Common stressors experienced by college students often pertain to school life, such as academic failure, and interpersonal relationships, including conflicts with roommates. Medical students, in particular, may face higher levels of stress due to the length of their schooling and clinical practice. These acute stressors can significantly disrupt mental well-being and potentially lead to the emergence of depressive episodes [
19]. Maladaptive emotion regulation strategies mediate the relationship between relational stress and challenging life events and depressive symptoms [
20]. On the basis of these factors, we propose our first hypothesis that depression may serve as an intermediary variable between negative life events faced by medical students and somatic symptoms.
To investigate the relationship between negative life events and somatic symptoms, we propose another potential pathway that is mediated by self-esteem. This is because self-esteem is a crucial aspect of an individual’s self-concept, which involves their overall assessment of their positive or negative value [
21]. People with low self-esteem often have a negative self-evaluation, leading to reduced confidence and courage in dealing with life’s challenges [
22]. Previous research has explored the mediating role of self-esteem and its impact on social life in different adolescent groups, including left-behind children [
23], college students [
24], and medical students [
25]. Negative life events can cause a decline in self-esteem, as reported in previous studies, while higher self-esteem has been associated with better social adaptation and increased peer trust and perceived social support [
26,
27]. Self-esteem has been shown to influence individual cognition, motivation, emotion, and behavior [
27]. Therefore, we propose our second hypothesis that self-esteem may mediate the relationship between negative life events faced by medical students and somatic symptoms.
According to the susceptibility model of depression, negative self-evaluation is considered a risk factor for depression [
28]. Since self-esteem is a core component of an individual’s self-evaluation, it may also have a negative predictive effect on depression. Previous research found that higher self-esteem can decrease the likelihood of an individual experiencing depression [
29]. Negative life events may cause low self-esteem [
26], which may exacerbate or even trigger depression, ultimately leading to somatic symptoms. Therefore, self-esteem and depression may have a chain relationship as mediators for negative life events leading to somatic symptoms.
The multiple mediation model is an approach that involves two or more mediation variables between independent and dependent variables. It has been widely used for analyzing the relationships in mental health [
30] and social behavior [
31]. This model has been shown promising performance in exploring the underlying mechanisms of the relationship between the independent and dependent variables. However, there are limited studies that have examined the association between negative life events and somatic symptoms while considering the self-esteem and depression of medical students, particularly among Chinese medical students. Therefore, this study investigates the serial multiple mediation of self-esteem and depression in the relationship between negative life events and somatic symptoms, with the aim of revealing how negative life events, as an external social factor, may act on somatization through internal cognitive and emotional psychological factors. Ultimately, this study will provide evidence for potential interventions that could alleviate somatic symptoms experienced by medical students.
4. Discussion
Somatic symptoms have received considerable attention among adolescents in recent years. Our study is the first to examine whether depression and self-esteem can moderate the relationship between negative life events and somatic symptoms among medical students in the north of China. The study yielded three important findings: First, the prevalence of somatic symptoms was high among medical students in China, and a significant correlation was found among negative life events, self-esteem, depression, and somatic symptoms. Second, different types of negative life events had varying predictive effects on somatic symptoms, with negative life events about interpersonal pressure having the most significant influence. Third, self-esteem and depression played roles to mediate negative life events and somatic symptoms, but only partially.
The study found that 68.97% of medical students experience somatic symptoms, underscoring the need for greater attention to the prevention and intervention of somatization in this population. The most commonly reported symptoms were general discomfort (including headache, dizziness, fatigue, and insomnia), consistent with previous findings [
36]. The questionnaire PHQ-15 involved 15 typical somatic symptoms and revealed that constipation, loose bowels, or diarrhea; feeling tired or having low energy; and nausea, gas, or indigestion were the top three symptoms reported. These symptoms may be attributed to the prolonged years of study, heavier academic burden, and the high-level requirements of medical education that medical students face in comparison to their peers. Additionally, medical students are a vulnerable population, as they must manage multiple stressors, which may contribute to the development of somatic distress [
37].
This study found that female medical students scored higher than male students in somatic symptom problems, which is consistent with the results in previous studies [
38,
39]. This gender difference may be attributed to females being more sensitive, vulnerable, and influenced by their surroundings, leading to a deeper perception of negative life events. Moreover, medical students who were not the only child faced more severe somatic symptoms, potentially due to the lack of parental support. Being the only one child in the family, the student may enjoy more resources and less life pressure, which can reduce the likelihood of developing somatic symptoms. Interestingly, medical students with higher living expenses experienced more severe somatic symptoms. However, the relationship between living expenses and somatic symptoms remains unclear, and further research is needed to explore potential influences, such as life experiences, eating habits, and school environment.
This study demonstrates a direct relationship between negative life events and somatic symptoms in medical students. The greater the number of negative life events experienced by medical students, the higher the likelihood of somatic symptoms. Additionally, the results indicate a significant correlation between depression and self-esteem with negative life events and somatic symptoms. Medical students with higher levels of depression reported more negative life events, more somatic symptoms, and lower self-esteem, while those with lower self-esteem showed more negative life events, somatic symptoms, and depression. These findings align with previous research; for example, a study on suicidality in Chinese medical students found a positive correlation between adverse life events, depressive symptoms, and somatic symptoms [
40]. Other studies have also demonstrated that individuals who grow up in environments with poor family harmony and support may be more susceptible to somatic disorders [
41,
42]. Furthermore, different levels of self-esteem are strongly associated with the development of depression, with self-esteem considered a risk factor for depression in young adults [
43]. Therefore, the correlations between negative life events, self-esteem, depression, and somatic symptoms are supported by extensive evidence.
To further examine the relationship between negative life events and somatic symptoms, we conducted regression analysis to test the predictive effect of different types of negative life events on somatic scores. The results showed that punishment, personal loss, interpersonal relationship pressure, and learning pressure had a positive predictive effect on somatization, while adaptive life events had a negative predictive effect. Of these, interpersonal stress had the most significant predictive effect on somatization. This finding is supported by previous research demonstrating that interpersonal factors are important predictors of somatic symptoms in the general population [
44]. Previous research found that interpersonal stress was significantly related to both psychological distress and somatic symptoms, both directly and indirectly through pathways mediated by loneliness [
45]. It is acknowledged that experiencing discrimination can be detrimental to one’s relationships, and research has shown that even ethnic microaggressions can lead to an increase in depression and somatic symptoms in adolescents [
46]. As college students mature, they become increasingly aware of the importance of interpersonal relationships, and the influence of interpersonal relationship pressure becomes more powerful. It is interesting to note that negative life events classified as academic stress were found to have the least predictive effect on somatic symptoms among medical students. It is understood that college students with many years of learning experience are more strongly influenced by psychological and social factors, such as interpersonal relationships, personal loss, punishment, and social adaptation. These results suggest the need to pay more attention to the different types of negative experiences that medical students face to decrease the level of somatic symptoms.
The primary objective of this study was to examine the moderating role of depression and self-esteem in the relationship between negative life events and somatic symptoms. By utilizing the Bootstrap method, we analyzed the chain-mediating model, and the results suggest that self-esteem and depression may play sequential and mediating roles between negative life events and somatic symptoms. All paths in the model were significant, with the exception of the association between self-esteem and somatic symptoms. Negative life events were found to have a direct effect on somatic symptoms and can be modulated by depression alone. Moreover, the sequence of negative events was found to first affect self-esteem, then depression, and, finally, somatic symptoms, as demonstrated by the chain of events.
Negative life events have been found to have a direct effect on depression, which is consistent with previous research demonstrating that negative life events can increase depression levels [
47]. Prior studies have also investigated the relationship between life events, depression, and somatic symptoms, with depression being identified as one of the primary factors contributing to the development of somatic complaints [
48]. According to symptom perception theory, bodily cues interact with psychological and environmental factors to produce perceived somatic symptoms, emphasizing the importance of examining these dimensions (negative life events, depression, and somatic symptoms) together [
45].
It is worth noting that the multiple mediating model of self-esteem and depression was a chain model rather than a parallel model, which does not show the characteristics of the composite multiple mediating model. Self-esteem and depression are strongly related [
49]. Two models tried to explain their nature of relation: the scar model stated that depression erodes self-esteem, while the vulnerability model stated that low self-esteem contributes to depression [
50]. A meta-analysis of longitudinal studies provided evidence for supporting the vulnerability model and indicated that the effect of self-esteem on depression was significantly stronger than the effect of depression on self-esteem [
50]. This finding can explain why the path of our multiple mediating model is from self-esteem to depression. It has been demonstrated that people with low self-esteem have more negative thoughts and memories when in a negative mood, whereas people with high self-esteem engage more in positive emotional thinking in order to alleviate their negative mood [
51]. This indicates that high self-esteem can be a kind of protector with the ability to adequately cope with these feelings, no longer developing into depression [
52]. Although there is a significant correlation between self-esteem and somatic symptoms, self-esteem cannot predict somatic symptoms directly. Based on this model, self-esteem shows its modulating effect on depression, and then, its function is transferred by depression to somatic symptoms. Previous studies have pointed out that the accumulation of negative life events can impair an individual’s cognitive function, leading to more depressive symptoms [
53]. External social factors may expand the influence through self-cognition, indicating that self-esteem will be affected by negative life events to some extent, and the decrease in self-esteem will increase the individual’s susceptibility to depression. The chain model between self-esteem and depression further proves that the interaction between both has an important effect on the development of somatic symptoms.