Prevalence and Correlates of Depressive Symptoms in Korean Adults: Results of a 2009 Korean Community Health Survey

Depression is one of the most common mental illnesses and a major public health concern throughout the world. According to the Global Burden of Disease study, depression ranks fourth in the world among causes of early death and disability, and is projected to become the second leading cause by 2020 (1, 2). In Korea, depression has also become a prominent social issue because of a rapid increase in suicides. The most recent report showed that the lifetime prevalence of major depressive disorder is 6.7% (4.8% in men and 9.1% in women), and has increased by 0.2% annually for the last decade (3).

To our knowledge, four representative published studies have reported the prevalence of depression in Korea using nationwide community samples (4-7). These epidemiological studies estimated the prevalence of depression and provided vital information for public mental health policy formulation in Korea. However, they had several methodological limitations. Some excluded people over 60 or 65 yr or collected their study samples from just 10 or 12 catchment areas (4-6). Another used a telephone survey method (7). All the studies also had sample sizes of only a few thousand people; these numbers could not reliably represent the general population of Korea.

In order to overcome these limitations, we analyzed data sets collected by the Korean Community Health Survey (KCHS) on individuals aged ≥ 19 yr in 16 metropolitan cities and provinces with 253 regional sites around the country in 2009 (8). The standardized questionnaire of the KCHS consisted of 358 questions in 13 fields and covered a wide variety of health topics including depression, which was assessed by the Korean version of the Center for Epidemiologic Studies Depression Scale (CES-D) (9).

Using data from the 2009 KCHS, we examined the prevalence of depressive symptoms and their association with sociodemographic factors, in the largest sample studied to date. The 2009 KCHS data allowed us to obtain a valid estimate of the prevalence of depressive symptoms and their correlates in Korea.

In this study, we found that the prevalences of depressive symptoms and definite depression were 11.0% and 3.7%, respectively. Comparing our results with those of previous nationwide epidemiologic studies, the prevalence of depressive symptoms found by us was much lower than that reported by Cho et al. (6) using the CES-D in 1998 (CES-D score of ≥ 16, 23.1% in males and 27.4% in females). However, the prevalence of definite depression obtained here is similar to those of recent epidemiological surveys of mental disorders in Korea using the Composite International Diagnostic Interview (CIDI). The results of these previous studies are summarized in Table 5.

Table 5
Representative nationwide studies on the prevalence of depression in Korea

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In general, previous studies using self-report depression scales such as CES-D or the Beck Depression Inventory (BDI) have yielded higher symptom scores and greater prevalence of depression in Korean samples than in Western countries (12). Culturally variable response styles among ethnic groups may be responsible for the difference (14, 15). Since we recorded a lower prevalence of depressive symptoms than previous studies using the same self-report scale (6, 16, 17) and a similar prevalence of definite depression to those of previous studies using fully structured interviews (4, 5), our findings raise the possibility that there has been a change of style of response to questionnaires for depression among Koreans over the last two decades. Increased awareness of depression and westernizing influences may have contributed to such a change.

The present study showed that females were 1.9 times more likely to have depressive symptoms than males. This is consistent with the fact that depressive disorders are twice as common in women as in men. Adverse experiences in childhood, depression and anxiety disorders in childhood and adolescence, socio-cultural roles and related adverse experiences, and psychological attributes affecting vulnerability to life events and coping skills are likely to be involved in the preponderance of depressive disorders in female (13). In addition, the hypothalamic-pituitary-adrenal (HPA) axis is more strongly activated in depressed women than in depressed men, and menopause, with the accompanying loss of estrogens, also causes the greatest disturbance of the HPA axis. It is possible that the constantly changing steroid milieu in women contributes to their vulnerability to depression (18).

We found that the prevalences of depressive symptoms and definite depression increased with age in both men and women. There is a great deal of evidences for increasing rate of depression as adults grow older. However, several previous studies have suggested that increasing age is not a risk factor for depression independent of the effects of other risk factors (19-23). Other risk factors associated with aging, such as poor physical health, not being married and low education level were found to be associated with depressive symptoms (23-25).

Interestingly, the results of this study show that the prevalences of depressive symptoms and definite depression were higher in people in their 20s than in those in their 30s. This finding is in accord with a recent review of epidemiologic studies on depression in Korea (12). Recently, youth unemployment has become a serious social problem across the world. The youth unemployment rate in Korea is also at a record high these days. Unemployment among the over 30s averages between 2 and 4%, whereas it is about at 7% or 8% among the under 30s (26). In addition, the problem of high tuition fees which has been raised by university students has become a sensitive political issue. According to OECD statistics, Korea has the second-highest tuition fees in the OECD, behind only the USA (27). These socio-environmental conditions may result in an increased psychological burden on young adults.

With regard to marital status, living with a spouse seems to be protective against depression in both genders. In particular, divorced men were about 3.5 times more likely to have depressive symptoms than males living with a spouse. The association of divorce with depressive symptoms was more pronounced in men (OR, 3.45; 95% CI, 3.15-3.75) than women (OR, 2.30; 95% CI, 2.13-2.49) on the basis of each reference condition. Disrupted marital status was more strongly associated with depressive symptom among men than among women. These findings agree with the longitudinal data from Statistics Canada's National Population Health Survey (NPHS) (28).

With regard to generational household composition, residing in multi-generational household is a risk factor for depressive symptoms. There is much evidence that depression is inversely related to the level of support, attachment, and approval adolescents experience in the family environment (29). However, the stress of living in multi-generational household may cause depressive symptom because of conflicts between family members.

In the present study, non-educated women were 2.7 times more likely to have depressive symptoms than women with college degrees. The association between lack of education and depressive symptoms was more pronounced in women (OR, 2.70; 95% CI, 2.49-2.93) than men (OR, 2.11; 95% CI, 1.91-2.33) on the basis of each reference condition. Individuals of higher socioeconomic position generally report lower levels of depression, regardless of their gender. Does education improve psychological well-being more for one sex than for the other? Data from a 1995 survey of US adults with follow-ups in 1998 and 2001 support the view that education improves well-being more for women, because socioeconomic disadvantage makes them depend more on education to achieve well-being. Depression decreases more steeply for women as their level of education increases than it does for men. The gender gap in depression essentially disappears among persons with a college degree or higher (30).

A greater prevalence of almost all major psychiatric disorders is associated with higher levels of urbanization (31). Our data showed that residents in metropolitan region were significantly more likely to have depressive symptoms than those living in the country side. This is in line with previous studies showing that psychiatric disorders are more prevalent and more complex among the inhabitants of more urbanized areas, probably due to various environmental stressors (32-35).

In conclusion, the present study provides a valid estimate of the prevalence of depressive symptoms in Korea, using the largest representative sample of Koreans to date. A relationship was found between depressive symptoms and various sociodemographic characteristics such as gender, marital status, generational household composition, education, income and type of dwelling place. The findings provide valuable help in formulation policies to sustain mental health in Korea. Further studies using various methods will be required to investigate the effects of sociodemographic factors and health-related behaviors on depression, and explore the causal relationships between them.