Introduction
Particularly during the COVID-19 pandemic, anxiety and depression are commonly prevalent mental health disorders [
1]. A higher prevalence of anxiety and depression was reported among adults [
2], hospital staff [
3], patients [
4], COVID-19 survivors [
5,
6], and the general population [
7,
8] during the pandemic. The same may be true for medical students, because, in addition to the same stress experienced by the general population [
1] and the students of other subjects [
9], medical students may have to face more stress during the pandemic unique to their specialty features such as the interruption of clinical rotation and clerkship [
10], which could make them more prone to develop mental health problems. Indeed, studies have demonstrated that anxiety and/or depression are highly prevalent in medical students [
11‐
13], and similar results have been found in our recent study on international medical students [
14]. In addition, a systematic review by Puthran [
15] and Quek [
16] showed alarmingly high prevalence of depression and anxiety respectively in medical students globally, compared to the general population, highlighting the importance of this research topic.
However, it is well known that anxiety and depression can co-occur in the same person, a condition often referred to as comorbid anxiety and depression (CAD). For example, one recent study has shown that over sixty percent of the participants with current anxiety or depressive disorder had a concurrent depression or anxiety disorder [
17], and the same phenomenon also exists in students [
18‐
20]. Anxiety and depression are known to be highly correlated, and they both exhibit a number of the same symptoms, including irritability, restlessness, poor concentration, irregular sleep patterns, and fatigue [
21]. Currently, there is no consensus on the mode of relationship between anxiety and depressive disorders in CAD, and three hypotheses have been put forward to illuminate the relationship: monism, dualism, and ternary theory. Monism is the idea that anxiety and depression in CAD belong to the same disease, that is, some researchers believe that anxiety symptoms are a part or whole of depression [
22,
23]; dualism is the idea that anxiety and depression are separate mental health disorders [
24]; while the ternary theory proposes that the coexistence of anxiety and depression is a third disease distinctive from an anxiety disorder or depressive disorder [
20]. Despite diverse ideas about the relationship between comorbid anxiety and depressive disorders, it is generally accepted that the adverse impact of CAD on individuals is more noticeable than the single anxiety or depressive disorders. For example, CAD would aggravate a person’s disease state and impair their response to treatment [
21,
25], and, compared with anxiety or depression alone, CAD was generally characterized by longer symptom duration, more chronicity, longer time to initial remission, and more recurrence [
17]. It was also known associated with functional, somatic, and other mental health problems such as less social activity, loneliness, chronic pain, cardiovascular disease, myocardial infarction, insomnia, obsessive–compulsive disorder, borderline personality disorder, and attempted suicide in comparison with single anxiety or depression [
17]. Therefore, CAD may represent more severe psychopathology or pathophysiology in contrast to anxiety or depression alone and should be given special attention. However, to our knowledge, there have been few reports on CAD for international medical students up to date.
Similarly, studies are needed to explore the related or predictive factors for CAD because these factors may be different from (albeit related to) those for anxiety or depression alone. Previous studies have shown that anxiety and depression are related to demographic factors. For instance, age, gender, and education levels were all related to anxiety/depressive symptoms among students [
13,
18,
20,
26,
27]. On the other hand, coping, which is defined as the cognitive attempts and behavioral adaption to cope with stressors [
28], has been linked to mental health issues, and those individuals who have negative coping styles are more likely to experience adverse outcomes [
29]. In addition, numerous research studies have demonstrated an association between perceived stress, which is the individual's self-assessment of the threat from stressors, and anxiety and depressive symptoms [
30,
31]. Additionally, psychological resources like optimism, resilience, and social support might play some roles as well. Social support helps people develop their behavioral patterns, social cognition, and values because it is the material or moral support that others provide to them when they are stressed out or in a difficult situation [
32]. A psychological resource that benefits a person's health is optimism, which is the human tendency to have optimistic expectations for the future [
33]. Last but not least, resilience is the capacity of an individual to grow in the face of stressors or negative changes [
34]. It has been demonstrated that these psychological tools positively help students who are anxious and depressed [
30,
35‐
38]. It is crucial to investigate all these pertinent psychosocial factors when addressing stress and the mental health issues it can cause so that we can offer the students comprehensive psychological assistance to ease their CAD symptoms.
Recent studies have found that compared to students in other subjects, medical students experience higher levels of anxiety and depression [
11,
19,
39]. Among medical students, the international medical students who study medicine in other countries instead of their own are deserving of even more special attention, because they may have issues of trans-cultural adaptation, residential separation from family, or the time differences for the online courses which demand quite an effort to catch up and sometimes can be stressful to them. We could foresee that these students' stress from the aforementioned sources might lead to mental health issues like CAD. But little research has been carried out to date to examine their functions in the mental well-being of international medical students, and we would like to fill the gap with our study. To that end, we are inspired to reprocess the data of our previous study [
14], and divide our study population into four categories according to their mental health conditions, namely, healthy (free from anxiety or depressive symptoms), anxiety, depression, and CAD. We hypothesize that stress brought on by the COVID-19 pandemic, a negative coping style, and perceived stress are all directly correlated to (CAD), whereas a good coping style, perceived social support, optimism, and resilience are negatively correlated. The overall objective of this research is to investigate the incidence of CAD among international medical students in China before identifying any potential variables that might predict CAD.
Methods
The current study is designed to be a cross-sectional study. Data were collected online at China Medical University during November 2020.
Recruitment
International medical students who are currently enrolled at China Medical University and have internet access and can fully comprehend the survey's content in English were the study's participants. Participants were contacted by email with a link to access the English informed consent letter and online questionnaire (N = 1030). Only by clicking “Agree” on the informed consent form can the questionnaire be answered. If the respondent does not click “Agree” on the informed consent form, he/she is deemed to have refused to participate in the study and cannot answer the questionnaire. In the end, 550 students completed the questionnaire.
Demographic data collection
The following were among the demographic data at the baseline: (1) General personal information: age, gender, academic background, residential place and style, current city-wide COVID-19 outbreak, smoking, consuming alcohol, exercising, staying up late, and Internet addiction; (2) stress associated to the COVID-19 pandemic: perception of the COVID-19 outbreak, worrying about oneself and family/friends/relatives contracting the illness, worrying about exam results, and concerns about not being able to finish studying.
Assessment of anxiety, depression, and CAD
Anxiety was evaluated via the Generalized Anxiety Disorder Assessment(GAD-7) [
40]. The GAD-7 score is calculated by assigning scores of 0, 1, 2, and 3, to the response categories of 'not at all', 'several days', 'more than half the days', and 'nearly every day', respectively, and adding together the scores for the seven questions. Scores of 5, 10, and 15 are taken as the cut-off points for mild, moderate and severe anxiety, respectively. In this study, participants with GAD-7 scores ≥ 5 indicated anxieties [
41]. Depression was evaluated via the Patient Health Questionnaire-9 (PHQ-9) [
42]. The PHQ-9 score is calculated by assigning scores of 0, 1, 2, and 3, to the response categories of 'not at all', 'several days', 'more than half the days', and 'nearly every day', respectively, and adding together the scores for the nine questions. Scores of 5, 10, 15, and 20 are taken as the cut-off points for mild, moderate, moderate-severe and severe depression, respectively. In this study, participants with PHQ-9 scores ≥ 5 were considered as having depression status [
42]. A participant was considered suffering from CAD when both criteria for defining anxiety and depression were met. In this study, GAD-7 and PHQ-9 were chosen for measuring anxiety and depression, respectively, because they were the most widely used scales with good validity and reliability in different populations.
Assessment of coping style, perceived stress, social support, optimism and resilience
In this study, five scales were used to measure coping style, perceived stress, social support, optimism and resilience, respectively. They were chosen because they showed good validity and reliability in different populations. The Simplified Coping Style Questionnaire (SCSQ) was employed to assess coping style [
43]. The SCSQ is a 20-item scale with two domains, positive coping style and negative coping style, and answer to each item was scored on a 4-point scale (0–3). Positive coping strategies demonstrated a positive coping style, while negative coping strategies demonstrated a negative coping style. A relatively high domain score indicated an inclination for using the appropriate coping mechanism.
The perceived stress levels were evaluated via the 10-item version of the Perceived Stress Scale (PSS-10) [
44]. On a 5-point scale, each item was scored. Higher scores imply a higher degree of perceived stress.
The Multidimensional Scale of Perceived Social Support (MSPSS) was employed for assessing the level of perceived social support among international medical students [
45]. A higher score on the MSPSS, a 12-item scale with a 7-point rating system, indicated greater social support.
Optimism was evaluated via the Revised Life Orientation Test (LOT-R) [
33]. It’s a ten items scale using a 5-point rating system. Three of the ten items were for optimism, three were for pessimism, and the remaining four items were fillers. A high score indicated a higher tendency for optimism.
The Resilience Scale-14 (RS-14) was employed for measuring resilience [
46]. It contains 14 items using Likert's 7-level scoring method. Scores that were higher implied greater resilience.
Operational definition
In the study, participants with only anxiety but not depressive symptoms were divided into the anxiety group; participants with only depressive but not anxiety symptoms were divided into the depression group; participants suffering from both anxiety and depressive symptoms were divided as comorbid anxiety and depression(CAD) group; participants with neither anxiety nor depressive symptoms were divided as a healthy group.
Statistical analysis
Data analysis was executed by employing the Statistical Package for Social Sciences (SPSS 20.0 for Windows). The level of 0.05 was considered the significance level for all statistical tests (2-tailed). For every continuous variable, normality and homogeneity of variance were first tested. The distributions of the categories for anxiety, depression, and CAD in the categorical demographic variables were described via the chi-square test. Nonparametric tests were employed for exploring the correlation among the anxiety group, depression group, CAD group, and the continuous variables (age, Covid-19 pandemic-related stress, positive and negative coping styles, perceived stress, perceived social support, optimism, and resilience). To identify the predictors, multinomial logistic regression analyses were performed. To avoid over-fitting the logistic regression models, the variables having
P < 0.2 in the Chi-square tests and nonparametric tests were added to the regression analysis [
47]. Data presented in the regression models comprised the regression coefficient (β), OR, and its 95% CI.
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