In the current study, we investigated the possible neural basis through which self-esteem was related to physical health. Our study not only reproduced the results that higher self-esteem was associated with better physical health, but also showed that the hippocampus mediated the link between self-esteem and physical health, suggesting its critical role in the neural circuit through which self-esteem is related to physical health.

Our study replicated previous findings that higher self-esteem is associated with better physical health2,10,11,12,13,43. Why is higher self-esteem link with better physical health? Several models used in health promotion or prevention offer insight into cognitive mechanisms that link self-esteem to health13,14,15,16. For example, the transactional model of stress and coping suggests that positive self-esteem can buffer stress by mitigating the perceived threat and by enhancing the selection and implementation of efficacious coping strategies, which in turn modulate physiological responses to stressors contributing to illness and physical health14. Generally, self-esteem can be seen as an internal moderator of stressors, and increasing the levels of self-esteem will reduce the incidence of illness15. Alternatively, the health behavior model has confirmed the role of self-esteem as a health behavioral determinant, that is, low self-esteem can trigger poor coping behavior or risk behavior that subsequently increases the likelihood of certain diseases, including mental disorders and physical diseases16,44. In fact, previous studies had verified that low levels of self-esteem was related to the incidence of health risk behaviors, such as smoking, alcohol consumption and drug use5,6,45, which may do harm to our health. Based on these models and evidences, self-esteem may be related to physical health by buffering the stress or increasing the health behaviors.

Our study showed that the GM volume of hippocampus was related to the individual difference in physical health in the healthy sample. The results extend the previous studies that have demonstrated the association between hippocampus volume and physical diseases such as hypertension and diabetes26,27. A large body of research has shown that the interaction of the hippocampus and the hypothalamic-pituitary-adrenal (HPA) axis might explain the onset of various illnesses25,46,47,48. The HPA axis has traditionally been regarded as the body’s stress tolerance and energy regulation system. Its hyperactivation is associated with excessive release of stress hormones (e.g. glucocorticoid, cortisol) and subsequently results in various health problems25,47. Meanwhile, the hippocampus activity has been suggested to exert a tonic inhibitory influence on the activation of HPA axis and subsequently decrease glucocorticoid secretion, and promote more efficient regulation of the HPA axis to ultimately promote physical health48.

Importantly, our study showed that self-esteem was associated with physical health through the hippocampus. This suggests that the hippocampus is a key node in the neural circuit underlying the link between self-esteem and physical health. In the face of stressful situations, the HPA axis, the autonomic nervous system, and the cardiovascular, metabolic, and immune systems interact with each other to achieve allostasis (adaptation) in the short term and lead to allostatic load (“the wear and tear on the body”) in the long term49. Allostatic load can result in altered brain architecture, especially in the hippocampus49. For example, there is evidence that prolonged stress which triggers the over release of glucocorticoids caused the atrophy of the hippocampus50,51,52,53,54,55,56,57. On the other hand, high self-esteem can help individuals to take effective coping strategies that buffers physiological responses to stressors17,20,22,23, and low self-esteem was related to higher cortisol response to stress task58 and lack of habituation to repeated stress exposure59. Consequently, high self-esteem can prevent the hippocampus from the harmful effects of allostatic load such as excessive glucocorticoids. Better preserved hippocampus in turn inhibits the prolonged excessive activity of the HPA, which can reduce allostatic load and guard against the disorders of neuroendocrine and immune systems, and ultimately promotes physical health46,60.

In sum, our study revealed the possible neural substrate underlying the association between physical health and self-esteem. Practically, given the protective role of self-esteem on physical health, it is recommended that its potential should be reconsidered in future health promotion programs. That is, a health promotion program should include a focus on fostering self-esteem, which can prevent an array of physical diseases. There are several issues unresolved in our study. First, the cross-sectional findings in the current study do not permit inference about the causal relationship among self-esteem, physical health, and the hippocampus, and future longitudinal studies are needed to provide better understanding for this topic. Secondly, we did not measure health behaviors in the current study and our results were inappropriate for providing neural constraints for the health behavior models. Therefore, future researches are needed to illuminate the neural mechanism through which physical health might be influenced by the interaction of self-esteem and health behaviors.