Introduction
Depression is an important public health problem that affects more than 300 million people worldwide. A study from Wang et al. (2023) has demonstrated that about 22% of college students in China suffer from depression, and the prevalence of depression among Chinese medical students is 27% ( Jin et al., 2022 ). So this shows that college students have an increasing risk of depression, the degree of which is higher than students in middle and elementary school, especially among medical college students ( Wang et al., 2023 ). Depression and anxiety are multifactorial and complex psychological problems with possible risk factors including psychological, academic, biological, lifestyle, social, and economic. In psychology, for example, students with higher neurotic and more introverted are more likely to be depressed from psychological view. Multiple college-related poor lifestyles such as smoking, drinking, and substance abuse also increase the risk of depression among college students. Having a supportive social network, like family and friendships, can also influence a student’s mood and reduce the likelihood of depression. If suffering from depression, students, especially medical students, are more likely to give up solving complex problems and feel confused during their studies ( Turana et al., 2022 ; Rengasamy et al., 2021 ; Mofatteh, 2021 ). These behaviors may lead to hypertension, obesity, diabetes, and other diseases in the future, which seriously reduce the quality of life and increase the economic burden ( Petersen et al., 2022 ). More importantly, the global suicide rate caused by depression is increasing every year and depression becomes a major risk factor for adolescents’ suicide ( Turana et al., 2022 ). According to existing studies, although there are many factors influence adolescents’ depression, such as anxiety, appearance satisfaction, interpersonal sensitivity, and social support, the complex relationships among the influencing factors are still unclear and need to be further investigated ( Kim, Han & Won, 2023 ; Xu et al., 2022 ; Bi & Wang, 2022 ; Zvolensky et al., 2021 ). Adolescence is a time when individuals go through major physical and psychological changes as they grow up, during which adolescents pay special attention to their image and are susceptible to the influence of the mass media’s aesthetic standards for appearance and figure. If they realize that they do not meet public social standards, they are prone to appearance anxiety, which is likely to lead to further depression ( Lim & Kwon, 2023 ).

Appearance anxiety (AA) refers to a condition when an individual is overly concerned about their appearance. They may become unconfident and anxious about their appearance when they perceive social standards or poor evaluations of themselves from others ( Gao et al., 2023 ). With the increasing rate of science and technology development, various social platforms and media have become flourishing and have been invading in college students’ lives ( de Vries et al., 2016 ). They gradually begin to pay excessive attention to their appearance and worry about others’ evaluation of their appearance. These may even trigger their anxiety ( Marengo et al., 2018 ). Some studies have pointed out that adolescence is a time in human development when they go through drastic physical and psychological changes. During adolescence, students pay more attention to their looks and are always unconsciously exposed to unrealistic standards of beauty, appearance, or body type from the mass media. Their self-esteem probably declines if they think that they do not meet these standards, resulting in anxiety and depression ( Hai & Yang, 2022 ). Appearance influences the formation and establishment of self-esteem in adolescence and young adulthood. Anxiety caused by appearance probably makes them negative due to a lack of confidence, which leads to a decrease in the level of self-esteem of the individual ( Lim & Kwon, 2023 ), resulting in an inability to integrate into society and to positively face the challenges of interpersonal relationships. Therefore, it is necessary to make a further study on the effect of AA on depression among medical college students in order to explore ways to reduce the rate of depression among them. Advances in a cognitive behavioral model of body dysmorphic disorder proposed that when individuals compare themselves to the least likely ideal appearance, they will be negative, which leads to self-protective behaviors such as avoidance ( Bilsky et al., 2022 ; Zimmer-Gembeck et al., 2021 ). Some adolescents may be bullied, harassed, and ridiculed because of their appearance, which exacerbates adolescents’ AA and gradually develops distorted perceptions and aversion to their own appearance ( Zimmer-Gembeck et al., 2021 ; Bucchianeri, Eisenberg & Neumark-Sztainer, 2013 ). When adolescents compare themselves upward with others or compare their ideal selves with their real-life selves, a discrepancy is created, which can lead to emotional vulnerability, anxiety and exacerbate depression ( Higgins, 1987 ; Festinger, 1954 ). Anabolic-androgenic steroid users are at greater risk of depression if they have defective appearances ( Griffiths et al., 2018 ). Dissatisfaction with physical appearance can act as a mediator to influence the relationship between self-esteem and depression ( Kim, Han & Won, 2023 ). Appearance influences the formation and establishment of self-esteem in adolescence and young adulthood. External anxiety can lead to a lack of confidence and negativity and further a decrease in an individual’s level of self-esteem, resulting in an inability to integrate into society and positively face the challenges of interpersonal relationships ( Liao et al., 2023 ). Hairi et al. found that a person’s dissatisfaction with his or her appearance can lead to lowered self-esteem, which in turn can trigger depression ( Hai & Yang, 2022 ). A study in Coimbatore showed that 77.6% of college women were dissatisfied with their body image and that depression was significantly associated with it ( Ganesan, Ravishankar & Ramalingam, 2018 ). At the same time, anxiety and depression are closely related--they are comorbidity, and anxiety is a risk factor for depression ( Belzer & Schneier, 2004 ). Studies have demonstrated that elevated levels of anxiety are associated with depression among college students in Latin America ( Zvolensky et al., 2021 ). Based on existing studies, it can be reasonably speculated that medical college students’ dissatisfaction with their appearance is likely to cause AA, which in turn increases the likelihood of depression.

Interpersonal sensitivity (IS) is one of the mental health problems faced by contemporary college students ( Ding et al., 2021 ). IS was first proposed by Boyce & Parker (1989) and is considered as a personality trait that usually manifests itself as an over-understanding of the behavior and emotions of others ( Masillo et al., 2012 ). Individuals sometimes pay too much attention to their own relationships and fear the rejection or criticism of others in social interactions, which is also a symptom of IS ( Xu et al., 2022 ). Discomfort and anxiety will happen in people with IS traits when they are interacting with people. Such discomfort leads to social anxiety and a strong sense of low esteem, making individuals vulnerable to developing depression. They also often change their behavior to conform to the expectations and ideas of others ( Boyce & Parker, 1989 ; Derogatis & Melisaratos, 1983 ). Some researchers have used structural equation modeling to show that IS moderates anxiety states in participants who are abused as children, and that also moderates AA in adolescents ( Maftei, 2022 ; Nakazawa et al., 2021 ). Among Chinese college students, negative emotion is related to IS and is one of the predictors of depression ( Xu et al., 2022 ; Ding et al., 2021 ). Whether IS can be used as a mediating variable to moderate the relationship between AA and depression among college students needs to be validated through further research.

Social support (SS) refers to a social network of family, friends, teachers, and classmates that provides emotional support and practical help to individuals ( Cohen, 2004 ). When encountering difficulties, college students can seek help from family, friends, etc ., so as to obtain solutions to problems, which greatly relieves physical and mental stress ( Xu et al., 2022 ). Therefore, SS is a key factor in the mental health of college students and makes an important contribution to the mental health of adolescents ( Wang et al., 2022 ; DuBois et al., 1994 ). Peirce et al. (2000) constructed a model based on social support theory and found that SS was negatively associated with depression. The study made by Jaycox et al. (2009) reported an effect of social interaction on depression in adolescents. SS can significantly reduce the anxiety levels of community residents during the COVID-19 outbreak in Turkey in 2020 ( Özmete & Pak, 2020 ). Body image and SS in patients with Psoriasis were found to be major contributors to depression ( Wojtyna et al., 2017 ). Meanwhile, SS plays an important role in reducing depressive symptoms and IS, and higher levels of SS can reduce the severity of an individual’s depressive symptoms and IS ( Mei et al., 2022 ).

Based on the available studies, it can be speculated that there is some relationship between AA, IS, SS, and depression. There are few studies on the mechanisms between AA and depression among Chinese college students, studying in a medical school, and there is a lack of studies demonstrating the mediating role of IS and SS in the relationship between AA and depression. Therefore, this study aimed to investigate the relationship between AA, IS, SS, and depression, as well as to explore the multiple mediating roles of IS and SS between AA and depression in medical college students. The purpose of this study is to reach a deeper understanding of the factors influencing depression and to provide a theoretical basis for the development of public health policies in relevant sectors. This is also to prevent depression at the source, consciously reduce the risk of depression among medical college students, and maintain their physical or mental health at a high level. Based on the above, the following three hypotheses are proposed: H1: AA positively predicts depression among college students studying in a medical school. H2: AA indirectly predicts depression through high IS among college students studying in a medical school. H3: AA indirectly predicts depression through low SS among college students studying in a medical school. H4: AA indirectly predicts depression through high IS and low SS among college students studying in a medical school.

H1: AA positively predicts depression among college students studying in a medical school.

H2: AA indirectly predicts depression through high IS among college students studying in a medical school.

H3: AA indirectly predicts depression through low SS among college students studying in a medical school.

H4: AA indirectly predicts depression through high IS and low SS among college students studying in a medical school.