A high frequency of depression and anxiety among medical students has been a major concern in medical education.1–3 A number of studies have been conducted on factors related to medical students' depression2–6 and the consequences of such depression.7–9 Higher academic load10 and working load,11,12 lack of sleep,12 exposure to patients' suffering and death,13 student abuse,14 financial concerns,12 and the hidden curriculum of cynicism15 have been suggested to contribute to poorer mental health for medical students compared with the general population. Research suggests that negative consequences of depression among medical students are poorer academic performance, alcohol and substance abuse, and suicide.6,16 Despite the higher prevalence rate and serious consequences of depression in medical students than the general population, only a low percentage of them actually seek treatment.3,5,17 In an earlier study, we demonstrated that medical students' age and knowledge about depression are relevant to their attitudes toward seeking treatment for their own depression.18 Taken together, it is important for medical schools to evaluate their students' depression and to encourage depressed students to receive proper treatment.
Lower prevalence of depression in Asian countries than in Western countries has been consistently reported by previous studies.19,20 Cross-cultural differences may influence how people experience and evaluate depressive symptoms, contributing to the differences in depression prevalence among countries.19,21 For instance, Koreans have shown a higher diagnostic threshold for major depressive disorder (MDD) than do Americans, which results in a lower prevalence of MDD in epidemiological studies.19 In addition, Koreans showed different symptom patterns. They are more likely to express symptoms of low energy and difficulty with concentration but are less likely to express depressed mood and ideations about death than Americans.19 Therefore, it can be supposed that the prevalence, possible risk factors, and consequences of depression for Korean medical students are likely to differ from those for their Western counterparts. Therefore, we initiated this study to evaluate the actual status of depression among Korean medical students. The accurate estimation of depression would serve as a milestone for formulating appropriate plans to prevent depression and its tragic consequences among medical students in Korea.
Although many informative studies about medical students' depression have been reported, most studies were single-centered or involved limited participation of students (e.g., first-year students or women only).6 In addition, most studies have estimated the prevalence of depression based on self-rating scales, such as the Beck Depression Inventory (BDI)22 or the Center for Epidemiological Studies Depression Scale (CES-D),23 that were originally developed for measuring severity of depressive symptoms, not for diagnosing depression.6 Recently, Dahlin and Runeson24 used a diagnostic tool, the Mini International Neuropsychiatric Interview (MINI), to evaluate depression among medical students. However, the study involved a limited number of students in the diagnostic interview (n = 81). In the present study, we conducted a nationwide, cross-sectional survey of all Korean medical students and estimated the prevalence of depression by using a diagnostic tool for depression, the patient-rated version of the MINI (MINI-PR).25 In addition, we examined social and personal correlates (gender, class year, and financial concerns) for their roles as possible risk factors for depression, and we also evaluated the influence of depression on academic performance.
In general, the medical curriculum in South Korea is similar to those of U.S. and Canadian medical schools. However, most Korean medical schools are undergraduate schools where students receive a total of six years of medical training comprising two years of premedical curriculum and four years of medical curriculum. The four years of medical curriculum comprise two years of preclinical work followed by two years of clinical work. Major and minor clinical rotation is arranged during the third and fourth year, respectively. The grade point average (GPA) in Korean medical schools is based on either a 4.0 or a 4.3 scale. Students who get either a GPA below 2.0 or “F” marks are not allowed to proceed to take courses in medical schools. In South Korea, students need to obtain top scores on the national college entrance exam, the College Scholastic Aptitude Test (CSAT), to be admitted to medical schools. Exceptions are those students who have lived and received education overseas for at least 12 years; they can apply for medical school with no CSAT requirement.
In 2006, we invited all 14,095 medical students registered in 41 medical schools in South Korea to participate in this cross-sectional nationwide survey. To adjust for the demographical differences between the responders and total Korean medical students, weights for gender and class year were calculated based on the 2006 medical school registry so that the sample would be representative of the target population.
We administered the survey at the end of the 2006 academic year in Korea, between December 2006 and January 2007. Prior to the survey, the study was reviewed and approved by the institutional review board of the Seoul National University Hospital. A postal packet containing survey questionnaires, information sheets, consent forms, and instructions for students was sent to all medical schools, and these forms were then handed out to the students and collected a week later. During the survey, nonrespondents did not receive any reminder of the survey. To ensure confidentiality, students who agreed to participate were directed to answer anonymously and to submit the completed questionnaires in a sealed envelope. Students who did not wish to participate were directed to simply submit the incomplete questionnaires in the same manner. After encoding data, we sent each medical school the data regarding their own students to inform them about the estimated prevalence of depression in their school.
The variables included in this study were depressive symptoms, sociodemographics, and academic functioning during medical school. We assessed depression with the major depressive episode module of the MINI-PR (v. 5.0.0),25 which was based on diagnostic criteria of the Diagnostic and Statistical Manual for Mental Disorders, fourth edition (DSM-IV). Nine questions derived from the nine DSM-IV symptoms of major depressive episode made up the major depressive episode module. Participants answered either “yes” or “no” to the questions. An acceptable level of agreement (kappa = 0.55) between the MINI-PR and Structured Clinical Interview for DSM-III-R diagnoses (SCID-P) for major depressive episode has been reported.25 We translated the major depressive episode module of the MINI-PR into the Korean language and found similar kappa coefficients between the MINI-PR and SCID-P for current, one-year, and lifetime MDD diagnoses (kappa = 0.59, 0.58, 0.64, respectively) in our previous study, which is under review for publication. We diagnosed MDD when students reported five or more depressive symptoms out of the nine DSM-IV symptoms of major depressive episode, with at least one of the symptoms being either depressed mood or loss of pleasure. The final diagnosis of current, one-year, or lifetime MDD was determined by the response to an additional question regarding the time of the depressive symptoms.
For the sociodemographic characteristics, we asked participants to identify their gender, age, medical school years, type of admission track, religion, marital status, financial status, and living arrangement. Academic functioning was measured by self-reported GPAs of the past year, having failing grades, GPA below 2.0, and leave of absence. We converted all GPAs to the 4.3 scale for this study. The questions regarding failing grades, GPA below 2.0, and leave of absence were yes/no questions. Possible reasons associated with leave of absence included poor academic performance or academic probation, physical or mental illnesses, and financial problems.
We used MS Access 2003 (Microsoft) to encode each response to minimize miscoding errors, and we used SPSS 13.0 (SPSS Inc., Chicago, Illinois) to analyze data. We applied Pearson chi-square analysis (5% significance level, two-tailed) to compare the prevalence of MDD between male and female students, as well as to compare the GPAs of the previous year between nondepressed and depressed students. We performed univariate and multivariate logistic regression analyses to determine the odds ratios (ORs) of having MDD in the previous year by certain possible risk factors. Finally, for respondents with one-year MDD, we performed multivariate logistic regression analyses to determine the ORs of poor academic functioning. Because depression prevalence markedly differs according to class years among medical students, we decided to analyze further for students with one-year MDD.
Of the participants whom we invited, 7,357 completed the survey (response rate of 52.2%). The responders consisted of a larger portion of female and first-year students and a smaller portion of fourth-year students as compared with the whole target population. As noted above, we calculated weights for gender and class year so that the sample would be representative of the target population. We present both weighted and unweighted sociodemographic data of the responders in Table 1.
The prevalence of depression among Korean medical students
The prevalence rate for experiencing current depression as reported by respondents was 2.9%, and the rates for those experiencing depression the previous year and during one's lifetime were 6.5% and 10.3%, respectively. For a more conservative estimation, sensitivity analysis can be applied. If we assume that all nonresponders did not have depression, the prevalence rate would be 1.5% for current, 3.3% for one-year, and 5.3% for lifetime depression. For male respondents, the current prevalence rate of depression was 2.6%, and the previous-year and lifetime rates were 5.5% and 9.0%, respectively. For females, the current prevalence rate of depression was 3.6%, and the previous-year and lifetime rates were 8.3% and 12.7%. Females showed a significantly higher rate of depression than males for current (χ2 = 5.7, df = 1, P < .05), one-year (χ2 = 22.8, df = 1, P < .001), and lifetime (χ2 = 25.1, df = 1, P < .001).
Possible risk factors of depression
Female gender, younger age, lower class years, admission track with exemption from entrance exam, living alone in a lodging house or a rented room, and financial difficulty significantly increased crude ORs of having MDD during the previous year (Table 2). When multivariate logistic analysis was applied, all of the above variables still significantly increased ORs of having MDD during the previous year. Among the variables, lower class years, admission track with exemption from entrance exam, and severe financial difficulty markedly increased the ORs of having MDD during the previous year. Students in their first year (OR 4.0, CI 2.8–5.6; P < .001), second year (OR 3.2, CI 2.3–4.6; P < .001), or third year (OR 2.2, CI 1.5–3.2; P < .001) of medical school showed higher ORs than those in their fourth year. Those who were exempted from taking the entrance exam showed 2.8 (CI 1.4–5.6) times higher OR than those who took the exam (P < .01), and those who experienced severe financial difficulty showed 2.2 (CI 1.5–3.3) times higher OR than those who did not (P < .001).
The impact of depression on academic performance
We explored how depression influenced students' academic performance by comparing the GPAs of nondepressed and depressed students in the two semesters of the year preceding our study (Table 3). Students who experienced MDD during the previous year scored significantly lower than nondepressed students in both semesters (t = 3.8, P < .001 and t = 4.8, P < .001 for the first and second semester, respectively). In addition, students with MDD had significantly lower academic grades for both male (t = 3.5, P < .01 and t = 2.8, P < .01 for the first and second semester, respectively) and female gender (t = 2. 8, P < .01 and t = 4.5, P < .001 for the first and second semester, respectively). Further, we analyzed whether MDD influenced temporary leave of absence, below-average grades (i.e., GPA below 2.0 on the scale of 4.3), or failing marks (Table 4). In Korea, students who get either a GPA below 2.0 or “F” marks are not allowed to proceed to take courses in medical schools. After adjusting for gender, class years, entrance exam, living arrangements, and financial difficulty, students who experienced MDD during the previous year, as compared with those without MDD, had ORs of 1.8 (CI 1.4–2.4) of having a GPA below 2.0 during the previous year (P < .001). Having MDD did not significantly increase the ORs of leave of absence and failing marks.
Our findings demonstrate that Korean medical students experience depression frequently. However, the prevalence rate of depression estimated by a diagnostic tool, the MINI-PR, in this study is much lower than those determined by the BDI or CES-D in other studies.1–3,5,9,17,26 It is noteworthy that Zoccolillo et al3 assessed the prevalence of depression with diagnostic interviews using the Diagnostic Interview Schedule and found a 6%–8% one-year prevalence rate of depression, which was similar to the 6.5% one-year prevalence rate that we found in this study. Yet, the response rate of 52% may have caused response bias in our study. Even though we do not know the influence of depression on response rate, we could hypothesize that the nonresponders would have a higher probability of having MDD than the responders, as depressed students with anergic symptoms may have failed to complete the survey or may have been absent from school during the survey because of depression. Or, to the contrary, students having MDD could have been more prone to respond to the survey because of their concerns about the problem.
Previous studies have suggested that the depression rate for medical students is higher than that for the general population.5,27 Our findings suggest that Korean medical students seem to have a higher prevalence of depression than those in the same age group in the general population. The one-year prevalence rate of depression among medical students (6.5%) is higher than that of the general population aged between 18 and 29 (1.5%) reported by the Korean Epidemiologic Catchment Area (KECA) study.28 However, a direct comparison between the two studies is not suitable, because the prevalence from the KECA study was estimated by direct interviews using the Korean version of the Composite International Diagnostic Interview 2.1.
Whether students' mental health declines during medical school and how their rate of depression changes over the years of training in medical school are yet unclear. Longitudinal studies, which have followed up on students for one, two, or four years, have suggested that depression rates increases during the first year and then peak during the second year, followed by a gradual decline during the later years of medical school.3,4,9,29,30 These findings suggest that medical education and training may be partly responsible for students' depression. In this study, we have found that students' first year in medical school presented the highest risk of depression, which then declined over the later years of medical education. Unlike U.S. and Canadian medical students, who start medical school after achieving a bachelor's degree, most Korean medical students take two years of premedical courses followed by a four-year medical curriculum. An abrupt increase in academic pressure and environmental demands in the first year of medical school compared with the premedical courses may contribute to the peak incidence of depression among the first-year students.
According to our findings, the prevalence of depression for female students was about 40% to 50% higher than for male students across all time frames. This corresponds with a higher lifetime prevalence of depression found in women among the general population.31 In previous studies, female students have shown higher depression scores or higher increases in depression scores during medical school.2,3,27,32 Contrary to such findings, some researchers have not found significant differences in depression scores between male and female students, and the reasons for such inconsistency remain to be elucidated.4,5,9,29,33
In addition to female gender and lower academic years, our findings show that the admission track with exemption from entrance exams, living at a lodging house or in a rented room, and financial difficulty were possible risk factors for depression among Korean medical students. The higher risk of depression among students who were admitted through a nonexam track compared with those who took an entrance exam may suggest that the current entrance exam is useful and discriminative in identifying individuals who are likely to successfully deal with the stress and challenges of the medical curriculum. A higher risk of depression among students living alone signifies the importance of supportive social networks as a protective factor against depression. Lastly, identifying financial difficulty as a possible risk factor for depression in our study confirms similar reports of previous studies.6
It has been assumed that higher mental distress such as depression in medical school results in poorer academic performance, or vice versa.9,10,34 We found that the GPAs of the previous year were significantly lower for students who were depressed during the past year than for those who were not. In addition, the OR of having poor GPAs was 1.8 times higher for students who were depressed during the previous year than for nondepressed students. Although these findings do not prove the causal relations between depression and academic functioning, they do suggest an association. Two prospective studies explored the possibility of a causal relationship and showed a strong association between depression and academic performance, but these studies showed mixed findings on the causality.9,10 Interestingly, they demonstrated the importance of pre-medical-school performance as a predictor of functioning well in medical school.9,10 These findings seem to be consistent with our finding that students who entered medical school without an entrance exam showed the highest OR of having MDD, taking a leave of absence, or having a poor GPA or “F” grades. The premedical academic performance of the students admitted without an entrance exam seems to be lower than that of the students admitted via entrance exam. Unexpectedly, having MDD did not significantly increase the ORs of having a leave of absence or “F” grades for our respondents. This finding could have resulted from a selection bias because students who were in their leave of absence or held back in a course because of a GPA below 2.0 or “F” grades could not participate and, therefore, were not included in this study. Therefore, a separate study needs to be carried out with those populations to examine the relation between depression and leave of absence or “F” grades.
In addition to response bias, discussed above, there are several limitations of the present study that should be considered. First, we should not dismiss the possibility that the cohort characteristics of each class year may have contributed to the differences in their depression rates. The cross-sectional design presented an additional limitation in terms of defining the causal relationship between depression and academic performance. A longitudinal cohort study is warranted to confirm the causal relationship suggested by our findings. Second, we determined the prevalence of depression using the MINI-PR, a self-administered diagnostic instrument. The use of self-reports is the most effective way to carry out large-scale surveys; however, the prevalence we found may be less accurate than that determined by clinical diagnoses with structured interviews. Third, although the response rate in our study was within an acceptable range, the possibility of a selection bias should be taken into account in interpreting the results of our study. We did not collect data from the students who dropped out of school prior to this survey. Because the rate of depression in the students who dropped out of school may have been higher than that in the students who were attending school, this may increase the risk of type II error. Fourth, female and first-year medical student responders were overrepresented by our sample compared with the target population, although we adjusted for the differences of gender and class year using weights. Fifth, another correlate of depression among medical students could be alcohol or drug abuse; this is also well known to be associated with poor academic performance. In this study, we did not investigate the incidence of substance use disorder and its relationship with depression among medical students.
This nationwide study is the first of its kind to present the prevalence of and possible risk factors for depression among Korean medical students. Similar to medical students in other countries, Korean medical students also experience depression frequently. Students who present multiple possible risk factors of depression identified in this study may require more careful attention by medical schools for prevention and early detection of depression. We have also highlighted the pervasive and strong association of depression with poor academic performance among medical students, while the causal relationship between depression and academic functioning needs further validation.
Although medical schools are responsible for graduating competent and healthy physicians, our findings demonstrate that a large number of students experience depression during medical school. To resolve this issue, medical schools should provide psychiatric services to assist students in need, consider reforming curricula to reduce stress in medical training, and develop programs for mental health and wellness to help students recognize personal distress and promote well-being. In particular, our findings suggest that first-year students in Korean medical schools need more attention to help them make smooth transitions between premedical and medical curricula. Additional research is warranted to develop specialized programs for facilitating early detection and treatment of depression and promoting psychological well-being among medical students.
This study was supported by a grant from the Korean Institute of Medicine, 2006–2007. The authors also thank the Korean Council of Deans of Medical College for their cooperation and support of this study.
This study was supported by a grant from the Korean Institute of Medicine, 2006–2007.
This study was reviewed and approved by the institutional review board of the Seoul National University Hospital.
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