Depressive disorder, one of the most common psychiatric disorders, tends to result in functional impairment. Mortality rates related to suicide are higher in patients with depression than in those with other mental diseases, and depression tends to recur. For these reasons, depression is considered to occupy an important position among mental disorders.¹

A recent epidemiological study in South Korea in 2006 found that the prevalence of major depressive disorder was 3.6% higher than the estimate from 2 years earlier.²

According to a cross-national epidemiological study of major depression, the lifetime prevalence of this disorder varies from 1.5% in Taiwan and 2.9% in Korea to 19.0% in Beirut.³ Ustun et al. also showed various prevalence rates in 15 countries, finding the highest rate in South America, the middle rate in the US and Europe, and the lowest rate in East Asia.⁴ Lower estimated prevalence rates in Asian than in Western countries reflect the influences of ethnicity, culture, and different research methodologies.⁵ The social stigma attached to depression contributes to the underestimation of the prevalence of depression in Korea. Indeed, the cultural context affects the way individuals express the disorder. Asian people tend to express depression as somatic symptoms, whereas Europeans and North Americans are prone to emphasizing more affective symptoms.⁶ Japanese women are likely to express emotional complaints by referring to physical problems or worries about childcare rather than by expressing depressed feelings.⁷ Chinese women frequently mention a "wind inside the head" and a "wind illness" as physical symptoms of depression.⁸

Using data based on the Korean version of the Center for Epidemiologic Studies Depression scales (CES-D), Kim et al.⁹ found a factor structure that differed from those reported in studies in Western countries.¹⁰ Namely, among Korean patients, somatic symptoms and affective symptoms were combined into one factor, and emotional hardship and interpersonal issues constituted another factor. The unique factor structure of depressive symptoms in Korean individuals suggests the need for different approaches to the diagnosis and treatment of depression in Korea.

According to a study investigating the current use of depression rating scales in a Korean mental health setting, psychiatrists and clinical psychologists use the Beck Depressive Inventory (BDI)¹¹ most frequently.¹²

The BDI, which is characterized by good reliability and validity, is widely favored in many countries. However, its items have limited ability to accurately screen for the symptoms of depression as expressed by Korean people. For instance, if questions addressing physical dimensions of depression are limited to topics such as sleep disturbances, changes in appetite and weight, and somatic concerns, they cannot detect somatic symptoms such as chest pain, hot flashes, and dizziness that are often reported by Korean patients with depressive disorder. The use of standardized Western tools may be culturally insensitive and increase the risk of overlooking symptoms or signs that are prevalent in non-Western cultures.^13,14 Therefore, it is necessary to develop a Korean tool for screening for depressive symptoms.

Many domestic studies have attempted to standardize depression rating scales developed in Western cultures such as the BDI, the CES-D, the Zung Self-Rating Depression Scale (SDS),¹⁵ and the Geriatric Depression Scale (GDS).¹⁶ However, no attempts to develop a domestic scale for depression have been reported thus far.

This study was designed to develop a culturally sensitive self-report scale, the Lee and Rhee Depression Scale (LRDS), to measure depressive symptoms and screen for depressive disorder in Korea.

A final sample of 3,697 control subjects and 448 patients with depression were enrolled in the current study after excluding data with random responses or unanswered questions.

All currently used tools for screening for depression in Korea originated in Western countries. Despite the good validity and reliability of those scales, they are limited in their ability to detect depressive symptoms in Korean patients given the many ethnic and cultural differences that affect mental disorders. Hence, the limitations of currently used Western tools may increase the risk of missing symptoms or signs in non-Western populations. This study attempted to develop a culturally sensitive measure to rate depression and to assess the validity and reliability of this measure.

This LRDS addressed six dimensions and posed five questions for each dimension, yielding a total of 30 questions. The results of the exploratory factor analysis showed that each dimension represented a single factor, and each dimension and the full scale reached satisfactory levels of reliability. The confirmatory factor analysis demonstrated a six-factor model consisting of negative thinking about the future, negative thinking about the self, worry and agitation, depressed mood, somatization, and loss of volition. We used the following overall measures of fit: 1) The χ², which tests the degree of agreement between a theoretical model and observed data but is sensitive to sample size.^29-30 Thus, some researchers suggest that the χ² may be reported but should not be used as a main index.³¹ 2) The root mean square error of approximation (RMSEA), an index for estimating the whole population using sampled data. A RMSEA value of 0.05 or less indicates good fit or high agreement between the whole population and the sample, 0.05-0.08 indicates moderate agreement, and 0.10 or higher indicates low agreement.^32,33 3) The comparative fit index (CFI), which ranges between 0 and 1. A value of 0.90 or higher indicates high agreement between data and hypothesis.^30,31,34 4) The root mean square residual (RMR) is the square root of the average squared amount by which the sample variances and covariances differ from their estimates. It indicates the mean correlation between the observed and hypothesized data that are not explained by the model. A low RMR indicates a high level of agreement between the hypothesis and the observed data. The measures of overall fit calculated in this study were all adequate (χ²=3381.59, RMSEA=0.06, RMR=0.04, standardized RMR=0.05, NFI=0.92, NNFI=0.91, CFI=0.92, and GFI=0.92). Thus, the RMSEA was less than 0.10, the standardized RMR was close to 0.05, and the CFI and GFI were over 0.90. These results suggest that the data reflected the six-factor model of the LRDS.

These data also indicated good concurrent validity in that they revealed significant and strong correlations with previously validated scales such as the BDI, HAM-D, and MMPI-D. According to a survey of mental health professionals about the current use of depression rating scales in Korean mental health settings, psychiatrists usually prefer the BDI and HAM-D, in that order, and clinical psychologists usually prefer the BDI and MMPI. This survey suggests that currently used depression rating scales are not various at clinical practice. Reasons for not using particular scales included doubts about reliability and validity, lack of familiarity with the scale, and ability to diagnose and assess via psychiatric interviews without the assistance of scales.¹² Given the current state of clinical practice in Korea, the development of a valid and reliable standardized depression rating scale for the Korean population should not be postponed. In this context, the LRDS, which is correlated with depression scales that have been validated on an international level, can be a helpful in screening for depression.

The LRDS is distinguished from existing scales such as the BDI with respect to items addressing somatic issues. Whereas the BDI contains items on sexual activity, work, fatigue, and health concerns, the LRDS contains the following items regarding somatic symptoms: 5) "My head aches and is heavy;" 11) "I feel pressure in my chest;" 17) "I have cold sweats and chills;" 23) "I have a fever in my whole body;" and 29) "My mouth is dry, and I have a bitter taste." These somatic symptoms are observed frequently among depressed people in Korea. Social stigma, such as the belief that "depression is a sign of a weak mind," leads individuals to express distress in somatic rather than emotional terms. Thus, many patients with depression are referred to psychiatry departments via departments of neurology and internal medicine. Therefore, the use of the LRDS to screen for depression will be useful not only in psychiatric but also in other departments of hospitals. Compared with the BDI, the LRDS can avoid response bias through positively worded items such as "My future will be happier than my life is now" and "I still feel that life is worth living." However, given that the LRDS contains no items pertaining to changes in appetite or sleep disturbances, which constitute common symptoms of depression, the use of both the BDI and the LRDS will increase true positives for depression.

In actual clinical practice, the accuracy with which depression is detected can be enhanced by using this scale with other depression scales. Lewinsohn and Teri³⁵ reported that the hit rate was higher when BDI was used with their depression scale. Lee and Song³⁶ also reported that the simultaneous use of both BDI and another depression scale decreased false positives compared with the use of BDI alone. Completing the 30 items of the LRDS in addition to the BDI-21 may be burdensome for patients in clinical settings, suggesting that future studies should attempt to decrease the number of items and assess the validity and reliability of the abbreviated instrument.

According to the ROC analysis, the diagnostic utility of this scale was 77.7%, indicating that it can be used to diagnose depression and to identify subjects experiencing depression for purposes of research. Use of this scale for research purposes will require specification of an objective cut-off score for classifying individuals into the depression group. It would be possible to find the relative position of each individual's depression score in a norm table prepared by calculating standard scores based on the means and standard deviations of groups by condition and then converting the scores into T-scores in which the mean is 50 and the standard deviation is 10.

In general, a T-score of 70 or higher is suggested as the threshold for depression, but we propose that scores +1.5 SD higher than the average T-scores be considered as indicative of depression. Indeed, use of this cut-off point in the present study would have placed 6.7% of the subjects into the depressed group. That is, if an individual's score was 65 or higher, he or she would be placed in the depression group; lower scores would place the individual in the non-depressed group. However, the cut-off score is not an absolute standard. The tester can use the norm table to choose an appropriate standard according to the purpose of the test. Indeed, the cut-off score can be set depending on the relative importance of false positives and false negatives. For example, if misclassifying non-depressed people as depressed (false positive) resulted in a serious situation, the possibility of false positives can be minimized by setting the cut-off score higher, and vice versa.

Individuals are classified on the LRDS based on the T-score table according to sex and age. According to the table presented in the Appendix, the cut-off score is 65 for males and 70 for females. It should be remembered that an individual with a high score should not necessarily be diagnosed with depression.

This study has the following limitations. First, this study attempted discriminant validation of the scale by comparing the total scores of a group of patients with depression with those of a control group. However, comparisons with other psychiatric disorders, such as an anxiety disorder, are needed to strengthen the discriminant validity. Second, we tested only the six-dimension model that we assumed would represent a good fit for the scale. Despite these limitations, the current study has important implications for future research. Although the internal consistency of this scale was satisfactory, its test-retest reliability should be studied to enhance its reliability. Furthermore, future investigations should examine other possible models including three-, four-, and five-factor models.

The current study is significant in that it is the first to develop a culturally sensitive scale for screening depression in Korea. The LRDS is not only valid and reliable, it also offers cut-off scores on the basis of age and sex; it is a useful and easy tool to administer in clinical and research settings.