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Prevalence of major depressive disorder in the general population of South Korea
JOURNAL OF PSYCHIATRIC RESEARCH
Journal of Psychiatric Research 40 (2006) 30–36
www.elsevier.com/locate/jpsychires
Prevalence of major depressive disorder in the general population of South Korea Maurice M. Ohayon a
a,*
, Seung-Chul Hong
b
Stanford Sleep Epidemiology Research Center, School of Medicine, Stanford University, 3430 W. Bayshore Road, Suite 102, Palo Alto, Stanford, CA 94303, USA b St. VincentÕs Hospital, Catholic University Medical College, Kyunggi Do, Korea Received 26 August 2004; revised 9 February 2005; accepted 22 February 2005
Abstract Introduction: Previous epidemiological studies have reported a high prevalence of major depressive disorder (MDD) in North America and Western Europe. However, little information exists on MDD in Asian countries. This study investigates the prevalence of MDD and its characteristics in the general population of South Korea. Methods: A representative sample of the South Korean general population composed of 3719 non-institutionalized individuals aged 15 years or older was interviewed by telephone using the Sleep–EVAL system. The participation rate was 91.4%. The interviews covered sociodemographic characteristics, health care utilization, physical illnesses and Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) psychiatric disorders. Results: A depressive mood, i.e., feeling sad, downcast, having the blues or having lost interest in things formerly pleasant was reported by 20.9% of the sample without significant difference between men and women and among age groups. DSM-IV MDD was found in 3.6% (95% CI: 3.0–4.2%) of the sample. The prevalence of MDD was comparable among age groups. Shift workers were more likely to have MDD than daytime workers. Factor significantly associated with MDD were: being a woman, being a light or heavy smoker, perceiving oneÕs health as being average or poor, doing physical activities at least three times per week in the evening, having a BMI below 18.5 kg/m2 and perceiving oneÕs life as being moderately or highly stressful. Conclusions: Prevalence of MDD in Korea is higher than what it was previously estimated to be two decades ago. The number of individuals seeking help for depression was very low, and only a small number of MDD subjects received appropriate treatment for their condition. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Epidemiology; Depression; Medical consultation; Gender; Age
1. Introduction Major depressive disorder (MDD) is a common psychiatric disorder and is an important cause of disability. In North America and Western Europe, it was estimated that between 2% and 6% of the adult general population had a MDD in the previous year or in the previous *
Corresponding author. Tel.: +1 650 494 1137; fax: +1 650 947 9813/650 493 1225. E-mail address: [email protected] (M.M. Ohayon). 0022-3956/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jpsychires.2005.02.003
month (Blazer et al., 1994; Dunlop et al., 2003; Jonas et al., 2003; Kessler et al., 2003; Meltzer et al., 1995; Ohayon et al., 1999a,b; Ohayon and Schatzberg, 2003; Regier et al., 1988; Weissman et al., 1996). Information on the prevalence of MDD in the general population of Asian countries is relatively scant and MDD was consistently reported to be lower than that observed in North America and Western Europe. Early estimates using DSM-III criteria set the lifetime prevalence between 0.9% and 3.4% in Hong Kong (China), Seoul (South Korea) and Taiwan (Chen et al., 1993;
M.M. Ohayon, S.-C. Hong / Journal of Psychiatric Research 40 (2006) 30–36
Hwu et al., 1989; Lee et al., 1990). More recently, a Japanese community survey (Gifu city) using the UM-CIDI reported a 6-month MDD prevalence of 1.2% and a lifetime MDD prevalence of 2.9% (Kawakami et al., 2004). This study aims to assess the point prevalence of DSM-IV MDD in the general population of Korea and the risk factors associated with MDD.
31
The participation rate was 91.4% (3719 completed interviews from 4067 eligible households) and the response rate was 86.1% (3719 completed interviews from 4321 contacted households). The final sample was composed of 3719 South Koreans representative of the targeted population. 2.2. Interviews
2. Methods 2.1. Sample The study has conducted between April and July 2001. The target population was non-institutionalized South Koreans aged 15 years or older. This represented 37,364,511 inhabitants. In 2001, 91.8% of South Korean households have the telephone and 79.4% had at least one cellular telephone according to the Korean National Statistical Office (www.nso.go.kr/eng/). A two-stage sampling design was used to draw the sample: In the first stage, a random sample of telephone numbers was drawn based upon the population distribution within the 16 provinces (Do) of South Korea and their counties (Gu). Inside each province, telephone numbers were randomly picked with respect to the size of the counties. In the second stage, during the initial telephone contact, the Kish sampling procedure (Kish, 1965) was used to select a household member. This method allows a random selection that maintains a representative sample in terms of age and gender and limits non-coverage error. The interviewer collected the age and gender of all eligible household members. The Sleep–EVAL system sorted the men and then the women by decreasing age and identified the person to interview based on one of the eight selection tables created by Kish. Each telephone number was assigned with one of the Kish tables. Individuals who did not speak Korean fluently, who suffered from hearing or speech impairment or an illness that precluded being interviewed were excluded from the study. Subjects who declined to participate or who gave up before completing half the interview were classified as refusals even though they might have met an exclusion criterion. Phone numbers were dialed at least 10 times at different times of the evening and on different days, including weekends, before being replaced. Overall, 8882 telephone numbers were used: 54% were rejected because it was a business, a fax or a number not in service (94.7%) and 254 potential participants had an exclusion criterion (97 had a speech or hearing impairment; 7 did not speak Korean; 36 were too ill to be interviewed and 114 had other limitations).
Interviews were conducted from 12 computer terminals located at St.VincentÕs Hospital (Kyunggi Do, South Korea). Interviewers inexperienced in psychiatric diagnosis but specially trained to use the Sleep–EVAL knowledge-based system performed the interviews. Their training lasted approximately 6 h. The training consisted mainly of role-playing, during which the interviewers practiced how to introduce the study and how to ask the questions and enter the answers on the computer. They were instructed to read the questions as they appeared on the monitor screen, to read all the answer choices and to never decide for the participant what was the most appropriate answer. Interviews lasted on average 37.08 (±20.12) min with a median of 32 min. The longest interviews involved subjects with sleep disorders associated with mental disorders. Interviews could be split over two or more sessions if the duration exceeded 60 min. Participants answered on average 233 (±67.84) questions (range: 66–464 questions). 2.3. Instrument Interviewers used the Sleep–EVAL knowledge-based expert system, (Ohayon, 1999, 1995a,b) to conduct the interviews on sleep and mental disorders. This computer system is specially designed to administer questionnaires and conduct epidemiological studies in the general population. The questionnaire was translated from the English version to the Korean version and then backs again into English language to ensure the questions kept the same meaning. The interviews began with a standard questionnaire seeking sociodemographic information, the sleep/wake schedule and the physical health status. Questions related to sleep and mental disease symptoms were also asked. Answers to these questions were used by the system to select a series of plausible diagnostic hypotheses (causal reasoning process). Each hypothesis was investigated with further questioning and deductions of the consequences of each answer. This process allowed the system to confirm or reject these hypotheses (nonmonotonic, level-2 feature). The system contained all questions required for entire diagnostic descriptions according to the International Classification of Sleep Disorders (ASDA, 1997) and the Diagnostic and
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M.M. Ohayon, S.-C. Hong / Journal of Psychiatric Research 40 (2006) 30–36
Statistical Manual of Mental Disorders, fourth edition (DSM-IV) (APA, 1994) classifications. The differential diagnosis process was based on a series of key rules allowing or prohibiting the co-occurrence of two diagnoses in accordance with ICSD and DSM-IV prescriptions. The interview ended once all diagnostic possibilities were exhausted. The system has been tested in various contexts: in clinical psychiatry and sleep disorders clinics. In psychiatry, the first study found overall kappas among the diagnoses of four psychiatrists and those of the system ranged from 0.44 with one psychiatrist to 0.78 with two psychiatrists (n = 114 cases) (Ohayon, 1995a,b). Kappa for major depressive disorder was 0.82 and kappa for bipolar disorder was 0.77. Overall kappa between psychiatrists and the system was 0.71 (Ohayon, 1995a,b). In another study that involved 91 forensic patients, most of the patients (60%) met criteria for a diagnosis in the psychosis spectrum. The kappa between diagnoses obtained by the system and those given by psychiatrists was 0.44 for specific psychotic disorders (mainly schizophrenia) (St-Onge and Ohayon, 1994). Other validation studies were also conducted specifically for sleep disorders (Hosn et al., 2000; Ohayon et al., 1999a,b).
This series of questions permitted evaluation of DSMIV criteria for a diagnosis of major depressive episode. 2.5. Statistical analyses Data were weighted to compensate for disparities between the final sample and the data of the official Korean census. Bivariate analyses involving categorical or qualitative variables were carried out with v2 statistics. Risk factors associated with MDD were analyzed using logistic regression (Hosmer and Lemeshow, 1989). Ninety-five percent confidence intervals were calculated for prevalence rates and odds ratios. Reported differences were significant at 0.05 or less.
3. Results The final sample is composed of 3719 subjects aged from 15 to 90 years old. Men composed 49.5% of the weighted sample (n = 1,842). Most subjects were married (63.7%) or single (32.9%). Separated or divorced participants represented less than 1% (0.2%) and widowed accounted for 3.2% of the sample. Subjects living in the metropolitan area of Seoul represented 22.6% of the sample.
2.4. Variables 3.1. Prevalence of depressive mood Information was collected about: sociodemographic information (age, gender, marital status, education, occupation), use of alcohol, tobacco, caffeine (quantity per day), health care utilization, current physical health status (presence of illnesses and perceived health quality), perceived level of stress, and social network. Depression was investigated with questions assessing: (1) if the subject was feeling sad, downcast or depressive; (2) feelings of hopelessness; (3) if the subject had lost interest and lacked pleasure in activities formerly considered pleasant. These questions were answered on an intensity scale (extremely, a lot, moderately, slightly, not at all, does not know), and then for each symptom whether it was present most of the day and nearly every day. Positive answers on one of these three questions triggered another series of questions that assessed: (1) changes in appetite or weight; (2) insomnia or hypersomnia symptoms (obtained with the help of the sleep questionnaire and supplemental questions to evaluate their appurtenance to depressive illness); (3) psychomotor agitation or retardation; (4) fatigue or loss of energy; (5) feelings of worthlessness or guilt; (6) difficulties in concentration or thinking, difficulties making decisions; (7) suicidal ideations. All these were rated by the subjects on the intensity scale used for the initial symptoms alone, as well as whether the symptom was present most of the day and nearly every day. The subjects also reported how long they experienced a depressive mood.
A total of 20.9% (95% confidence interval: 19.6– 22.2%) of the sample reported feeling sad, downcast, having the blues or having lost interest in things formerly pleasant at the time of the interview. The prevalence was comparable between men (20.4%) and women (21.5%) and among the six age groups. 3.2. Prevalence of major depressive disorders Major depressive disorders (MDD) were found in 3.6% (95% CI: 3.0–4.2%) of the sample (point prevalence). The prevalence was comparable between men and women and among age groups (Table 1). Similarly, marital status and level of education were not associated with MDD. A higher prevalence of MDD was found in shift/night workers compared to daytime workers. Similarly, individuals living in Seoul metropolitan city, Kyeongsangnam, Kyongsangbuk or Chungchongnam provinces were more likely to have a MDD than those living in the Kwangju, Kangwon and Chollabuk provinces (Table 1). A major depressive episode lasted on average 32 weeks. 3.3. Factors associated with major depressive disorders A logistic regression was performed to identify factors associated with MDD. Variables entered in the
M.M. Ohayon, S.-C. Hong / Journal of Psychiatric Research 40 (2006) 30–36 Table 1 Point prevalence of major depressive disorders by sociodemographic characteristics
Gender Male Female Age groups (yrs) 15–24 25–34 35–44 45–54 55–64 >=65
N
Prevalence
95%CI
1842 1877
3.2 4.0
[2.4–4.0] [3.2–4.9]
779 899 841 500 386 313
3.8 3.1 4.2 4.1 2.1 4.6
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Table 2 Factors associated with major depressive disorders – multiple logistic regression model Prevalence of Adjusted MDD
ORa
95%CI
Sig.
Gender Male Female
3.2 4.0
1.00 1.59
[0.96–2.63]
0.07 n.s.
[2.4–5.1] [2.0–4.2] [2.8–5.5] [2.3–5.8] [0.7–3.6] [2.3–7.0]
Occupation Daytime work Shift/night work Not working Student
2.4 6.5 3.7 3.6
1.00 1.89 1.40 1.79
[0.99–3.61] [0.79–2.48] [0.72–4.47]
0.055 n.s. n.s. n.s.
1.00 1.92 0.76 4.48
[1.06–3.48] [0.33–1.78] [1.42–14.12]
0.031 n.s. 0.011
Marital status Not Married Married
1335 2345
4.3 3.3
[3.2–5.4] [2.6–4.1]
Education Never went to school <11 yrs schooling 12 yrs schooling Non-university grade Some university
Number cigarettes per day Non-smoker 3.2 <15 5.7 15–24 2.9 >=25 16.4
222 676 1110 938 732
3.4 4.4 3.2 3.5 4.0
[1.0–5.9] [2.9–6.0] [2.2–4.2] [2.4–4.7] [2.6–5.4]
Level of stress Low Moderate High
1.5 4.8 14.6
1.00 2.68 7.40
[1.65–4.35] [4.50–12.16]
0.001 0.001
Health status Good Average Poor
2.0 7.6 19.6
1.00 2.40 7.17
[1.52–3.77] [3.99–12.88]
0.001 0.001
Number of medical consultations last year None 1.00 1 1.11 >=2 1.62
[0.42–2.93] [0.99–2.64]
n.s. 0.054
Physical activities No physical activity Daytime Evening
[0.54–1.29] [1.03–3.19]
n.s. 0.04
[1.63–4.86]
0.001
[0.56–2.13] [0.10–7.54]
n.s. n.s.
Occupation Daytime work Shift/night work Not working Student Areas Seoul metropolitan city Kuonggi province Pusan metropolitan city Kyeongsangnam province Daegu metropolitan city Inchon metropolitan city Kyongsangbuk province Chollanam province Chollabuk province Chungchongnam province Kangwon province Chungchongbuk province Kwangju metropolitan city Daejon metropolitan city Ulsan metropolitan city Chdju province a b c
992 420 1570 737
2.4 6.5a 3.7 3.6
[1.5–3.4] [4.1–8.9] [2.8–4.6] [2.2–4.9]
844 693 288 230 198 197 186 171 161 155 134 125 113 108 77 39
4.8b 2.7 3.4 8.3b 2.5 3.7 5.8c 1.5 0.9 7.5b 0.6 2.7 0.3 2.6 0.9 2.0
[3.4–6.3] [1.5–3.9] [1.3–5.6] [4.7–11.9] [0.3–4.7] [1.0–6.3] [2.4–9.1] [0.0–3.4] [0.0–2.4] [3.3–11.7] [0.0–2.0] [0.0–5.5] [0.0–1.2] [0.0–5.6] [0.0–3.0] [0.0–6.6]
p < 0.01 With daytime work. p < 0.01 With Kwangju, Kangwon, Chollabuk and Ulsan. p < 0.05 With Kwangju, Kangwon and Chollabuk.
model were: age, gender, marital status, education level, occupation, geographic areas, BMI, number of glasses of alcohol per day, number of cigarettes per day, number of cups of coffee/tea per day, perceived health status, number of medical consultations in the previous year, presence of physical disease, perceived stress, and level of satisfaction with the social network. Significant variables associated with MDD are presented in Table 2. These variables were being a light or heavy smoker, perceiving oneÕs health as being average or poor, doing physical activities at least three times
3.4 3.2 7.0
1.00 0.84 1.81
Body mass index (kg/m2) <18.5 8.2 18.5–24.9 3.2 25–29.9 3.3 >= 30 2.6
2.81 1.00 1.10 0.85
Non-significant variables were age, geographic areas, coffee intake, alcohol intake, level of satisfaction with social life. a Model adjusted for effect of one on each other variable.
per week in the evening, having a BMI below 18.5 kg/m2 and perceiving oneÕs life as being moderately or highly stressful. Being a shift or night worker and having consulted at least two times a physician in the previous year were marginally significant. 3.4. Medical consultations and treatment Only 15.7% of the sample had consulted a physician in the previous 12 months. MDD subjects were more likely to have consulted (31.9%) than the remaining individuals of the sample (15.1%; p<0.0001). However, consultation for depressive mood was very low: only 2.2% of MDD subjects reported that depressive mood was a
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motive for consultation. Antidepressant treatment was also infrequent: only 7.4% of MDD subjects were currently taking this type of treatment.
4. Discussion This epidemiological study is the first to assess the prevalence of major depressive disorder in Korea in nearly two decades and is the first nationwide South Korean study to use DSM-IV criteria. A nationwide study was performed in 1995 but was limited to depressive symptoms assessed with the CES-D (Cho et al., 1998). We found the point prevalence of major depressive disorder to be 3.6%, which is higher than what was reported earlier in Korea: The study of Lee et al., conducted in 1984 (Lee et al., 1990) reported a 12-month prevalence of 2.3% and a lifetime prevalence of 3.4%. It is also higher than the prevalence reported in other Asian countries. For example, the WHO consortium (Demyttenaere et al., 2004) reported a 12-month prevalence of mood disorders at 2.5% in Beijing (China) and 1.7% in Shangai (China). However, China is a developing country while South Korea is an industrialized country, with 60% of the households with at least one computer and 75.4% with Internet access. In Japan, Kawakami et al. (2004) reported a 6-month prevalence of MDD at 1.2%. However, in that study, the participation rate was low (56.9%) and it was done in a mediumsize city (Gifu city) of 410,036 inhabitants. In our study, we also found a lower rate of MDD in smaller cities and provinces. Our rate, however, is lower than the prevalence found in recent North American studies: a 30-day prevalence of 4.9% (Blazer et al., 1994) and a 12-month prevalence of 6.6% (Kessler et al., 2003). Our rate is lower than or comparable to prevalences observed in Western European countries (Andrade et al., 2003; Ayuso-Mateos et al., 2001; Ohayon et al., 1999a,b). For example, the ESEMeD study using the CIDI and including six European countries (Italy, Spain, the Netherlands, Belgium, France and Germany) reported a 12-month prevalence of MDD at 3.9% (Alonso et al., 2004). However, this study also had low participation rates in four of the six countries surveyed (45.9–57.8%). Using the same tool as in this study, Ohayon and Schatzberg (2003) found a prevalence of MDD at 4.0% in their European sample of 18,980 subjects. We did not find significant changes associated with gender and age as reported in many North American or European studies. This lack of association is not unique to our study and was also reported in other Asian studies (Kawakami et al., 2004; Weissman et al., 1996). The comparison with other studies is obviously complicated by the fact that we did not use the WHO-CIDI or its variants. The structure of the Sleep–EVAL ques-
tionnaire, however, is similar to that of the CIDI in the sense that the evaluation of MDD began with a series of three questions on current depressive mood and loss of interest and pleasure. Negative answers to these questions stopped the exploration of depressive disorders. There is also the possibility that the method of answering the questions influenced the prevalence. In the CIDI, questions are answered by ‘‘yes’’ or ‘‘no.’’ In the Sleep–EVAL system, questions are mostly answered on scales (frequency, severity or modulated yes/no, for example, rather yes or rather no). As stressed by Noh and Chen (1998, 1992) and Jang et al. (2001), Korean individuals are sensitive to response style. For example, while it is all right for an American or a European to affirm he is happy with his life, it is not socially acceptable to do so for a Korean. Therefore, there is the possibility that the direct approach of the Western way to assess mental disorders is less appropriate and less effective with Asian people. However, more crosscultural research is still needed to improve our understanding of cultural differences in the assessment of mental disorders. Our presentation of the study to the participants was also different; the first aim of our study was to investigate sleep disorders in the population and was presented as such to the participants. The first half of the interview was used to collect information on sleep habits, sleep disturbances, health and health care utilization. Questions about mental health issues appeared later in the interview; this may have helped to alleviate the stigma associated with psychiatric disorders. While the majority of South Korean households have a telephone (91.8%) or a cellular phone (79.4%), the rate is lower in the poorest households: In households earning less than 12,000 USD per year, 85.3% had a telephone and 51.5% had a cellular telephone. Therefore, there is a chance that we have under-sampled the poorest households. The South Korean society has undergone several changes in the past three decades. The rapid economic growth and industrialization of the country are likely to have had a harder effect on some segments of the population, such as the elderly, for whom a social security system is nearly non-existent. Once they reach the age of retirement, the Korean elderly often have to rely on family support or are living in poverty. This could partly explain why we found a high rate of MDD (4.6%) in subjects 65 years or older, while in Western countries the prevalence of MDD decreases with age (Andrade et al., 2003; Kessler et al., 2003). Similarly, shift/night work, dissatisfaction with work and stressful life were associated with a high prevalence of MDD in our sample (respectively, 6.5%, 9.7% and 14.6%). Shift and night work as well as poor job satisfaction have been proven to be associated with poor mental health status in sev-
M.M. Ohayon, S.-C. Hong / Journal of Psychiatric Research 40 (2006) 30–36
eral studies (Bildt and Michelsen, 2002; Shigemi et al., 1997) and to the development of depression (Bildt and Michelsen, 2002). Association between MDD and physical exercise in the evening was mostly due to shift and night work: we found that 22.2% of shift and night workers who exercised in evening had a MDD. The percentage of the sample that consulted a physician is very low in our sample even though Korea has national health insurance with universal coverage of the population. Until July 2000, there was no separation of drug prescription and dispensing: Both physicians and pharmacists prescribed and dispensed drugs. Many people see a pharmacist initially for minor health problems. Therefore, pharmacists often act as a first-line health-care provider. A direct consequence of this practice was that few subjects with a MDD consulted a physician and fewer had an appropriate treatment for their depressive disorder. This situation is not unique to Korea; even in countries where drug prescription is made solely by physicians, a sizeable number of patients with major depressive disorder go undetected and remain untreated. In conclusion, new research directions are needed in this field: Comparison with other Asian countries, family studies, impact of pain on depression are of interest. Characterizing the specificity of depression symptomatology in comparison to Western countries could be a way to find invariant factors and patterns of depression across cultures.
Acknowledgment This study was supported by unrestricted educational grants from Lilly-Korea and Sanofi-Synthelabo Korea.
References Alonso J, Angermeyer MC, Bernert S, Bruffaerts R, Brugha TS, Bryson H, et al. ESEMeD/MHEDEA2000 investigators, European study of the epidemiology of mental disorders (ESEMeD) project. 12-month comorbidity patterns and associated factors in Europe: results from the European study of the epidemiology of mental disorders (ESEMeD) project. Acta Psychiatrica Scandinavica Suppl 2004(420):28–37. Andrade L, Caraveo-Anduaga JJ, Berglund P, Bijl RV, De Graaf R, Vollebergh W, Dragomirecka E, Kohn R, Keller M, Kessler RC, Kawakami N, Kilic C, Offord D, Ustun TB, Wittchen HU. The epidemiology of major depressive episodes: results from the International Consortium of Psychiatric Epidemiology (ICPE) Surveys. International Journal of Methods in Psychiatric Research 2003;12:3–21. American Psychiatric Association (APA). Diagnostic and statistical manual of mental disorders. fourth ed. Washington: The American Psychiatric Association; 1994. Ayuso-Mateos JL, Vazquez-Barquero JL, Dowrick C, Lehtinen V, Dalgard OS, Casey P, Wilkinson C, Lasa L, Page H, Dunn G, Wilkinson GODIN Group. Depressive disorders in Europe:
35
prevalence figures from the ODIN study. British Journal of Psychiatry 2001;179:308–16. Bildt C, Michelsen H. Gender differences in the effects from working conditions on mental health: a 4-year follow-up. International Archives of Occupational and Environmental Health 2002;75:252–8. Blazer DG, Kessler RC, McGonagle KA, Swartz MS. The prevalence and distribution of major depression in a national community sample: the National Comorbidity Survey. American Journal of Psychiatry 1994;151:979–86. Chen CN, Wong J, Lee N, Chan-Ho Lau J, Fung M. The Shatin Community Mental Health Survey in Hong Kong. II. Major findings. Archives of General Psychiatry 1993;50:125–33. Cho MJ, Nam JJ, Suh GH. Prevalence of symptoms of depression in a nationwide sample of Korean adults. Psychiatry Research 1998;81:341–52. Demyttenaere K, Bruffaerts R, Posada-Villa J, Gasquet I, Kovess V, Lepine JP, et al. WHO World Mental Health Survey Consortium. Prevalence, severity, and unmet need for treatment of mental disorders in the World Health Organization World Mental Health Surveys. JAMA 2004;291(21):2581–90. Dunlop DD, Song J, Lyons JS, Manheim LM, Chang RW. Racial/ ethnic differences in rates of depression among preretirement adults. American Journal of Public Health 2003;93:1945–52. Hosmer DW, Lemeshow S. Applied logistic regression. New-York: Wiley; 1989. Hosn R, Shapiro CM, Ohayon MM. Diagnostic concordance between sleep specialists and the Sleep–EVAL system in routine clinical evaluations. Abstract Journal of Sleep Research 2000;9(Suppl. 1): 86. Hwu HG, Yeh EK, Chang LY. Prevalence of psychiatric disorders in Taiwan defined by the Chinese diagnostic interview schedule. Acta Psychiatrica Scandinavica 1989;79:136–47. ICSD – International Classification of Sleep Disorders: Diagnostic and Coding Manual (ICSD). Rochester and Minnesota: American Sleep Disorders Association; 1997. Jang Y, Small BJ, Haley WE. Cross-cultural comparability of the geriatric depression scale: comparison between older Koreans and older Americans. Aging and Mental Health 2001;5:31–7. Jonas BS, Brody D, Roper M, Narrow WE. Prevalence of mood disorders in a national sample of young American adults. Social Psychiatry and Psychiatric Epidemiology 2003;38:618–24. Kawakami N, Shimizu H, Haratani T, Iwata N, Kitamura T. Lifetime and 6-month prevalence of DSM-III-R psychiatric disorders in an urban community in Japan. Psychiatry Research 2004;121:293–301. Kessler RC, Berglund P, Demler O, Jin R, Koretz D, Merikangas KR, Rush AJ, Walters EE, Wang PS. The epidemiology of major depressive disorder: results from the National Comorbidity Survey Replication (NCS-R). JAMA 2003;289:3095–105. Kish L. Survey sampling. New York: Wiley; 1965. Lee CK, Kwak YS, Yamamoto J, Rhee H, Kim YS, Han JH, Choi JO, Lee YH. Psychiatric epidemiology in Korea. Part I: gender and age differences in Seoul. Journal of Nervous and Mental Disease 1990;178:242–6. Meltzer H, Gill B, Petticrew M, Hinds K. The prevalence of psychiatric morbidity among adults living in private households. OPCS Surveys of Psychiatric Morbidity in Great Britain: Report 1. London: HMSO; 1995. Noh S, Chen X. Measuring depression in Korean immigrants: assessing validity of the translated Korean version of CES-D scale. Cross-cultural Research 1998;82:358–77. Noh S, Avison W, Kaspar V. Depressive symptoms among Korean immigrants: assessment of a translation of the CES-D. Psychological Assessment 1992;4:84–91.
36
M.M. Ohayon, S.-C. Hong / Journal of Psychiatric Research 40 (2006) 30–36
Ohayon M. Knowledge based system Sleep–EVAL: decisional trees and questionnaires. Ottawa: National Library of Canada; 1995a. Ohayon M. Validation of expert systems: examples and considerations. Medinfo 1995b;8:1071–5. Ohayon M. Improving decision making processes with the fuzzy logic approach in the epidemiology of sleep disorders. Journal of Psychosomatic Research 1999;47:297–311. Ohayon MM, Guilleminault C, Zulley J, Palombini L, Raab H. Validation of the Sleep–EVAL system against clinical assessments of sleep disorders and polysomnographic data. Sleep 1999a;22:925–30. Ohayon MM, Priest RG, Guilleminault C, Caulet M. The prevalence of depressive disorders in the United Kingdom. Biological Psychiatry 1999b;45:300–7. Ohayon MM, Schatzberg AF. Using chronic pain to predict depressive morbidity in the general population. Archives of General Psychiatry 2003;60:39–47.
Regier DA, Boyd JH, Burke Jr JD, Rae DS, Myers JK, Kramer M, Robins LN, George LK, Karno M, Locke BZ. One-month prevalence of mental disorders in the United States: based on five epidemiologic catchment area sites. Archives of General Psychiatry 1988;45:977–86. Shigemi J, Mino Y, Tsuda T, Babazono A, Aoyama H. The relationship between job stress and mental health at work. Industrial Health 1997;35:29–35. St-Onge B, Ohayon M. LÕutilisation du syste`me Expertal dans un milieu de psychiatrie le´gale. Abre´ge´s du Congre`s de Psychiatrie et de Neurologie de Langue Franc¸aise 1994:112. Weissman MM, Bland RC, Canino GJ, Faravelli C, Greenwald S, Hwu HG, Joyce PR, Karam EG, Lee CK, Lellouch J, Lepine JP, Newman SC, Rubio-Stipec M, Wells JE, Wickramaratne PJ, Wittchen H, Yeh EK. Cross-national epidemiology of major depression and bipolar disorder. JAMA 1996;276(4):293–9.
Journal of Psychiatric Research 40 (2006) 30–36
www.elsevier.com/locate/jpsychires
Prevalence of major depressive disorder in the general population of South Korea Maurice M. Ohayon a
a,*
, Seung-Chul Hong
b
Stanford Sleep Epidemiology Research Center, School of Medicine, Stanford University, 3430 W. Bayshore Road, Suite 102, Palo Alto, Stanford, CA 94303, USA b St. VincentÕs Hospital, Catholic University Medical College, Kyunggi Do, Korea Received 26 August 2004; revised 9 February 2005; accepted 22 February 2005
Abstract Introduction: Previous epidemiological studies have reported a high prevalence of major depressive disorder (MDD) in North America and Western Europe. However, little information exists on MDD in Asian countries. This study investigates the prevalence of MDD and its characteristics in the general population of South Korea. Methods: A representative sample of the South Korean general population composed of 3719 non-institutionalized individuals aged 15 years or older was interviewed by telephone using the Sleep–EVAL system. The participation rate was 91.4%. The interviews covered sociodemographic characteristics, health care utilization, physical illnesses and Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) psychiatric disorders. Results: A depressive mood, i.e., feeling sad, downcast, having the blues or having lost interest in things formerly pleasant was reported by 20.9% of the sample without significant difference between men and women and among age groups. DSM-IV MDD was found in 3.6% (95% CI: 3.0–4.2%) of the sample. The prevalence of MDD was comparable among age groups. Shift workers were more likely to have MDD than daytime workers. Factor significantly associated with MDD were: being a woman, being a light or heavy smoker, perceiving oneÕs health as being average or poor, doing physical activities at least three times per week in the evening, having a BMI below 18.5 kg/m2 and perceiving oneÕs life as being moderately or highly stressful. Conclusions: Prevalence of MDD in Korea is higher than what it was previously estimated to be two decades ago. The number of individuals seeking help for depression was very low, and only a small number of MDD subjects received appropriate treatment for their condition. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Epidemiology; Depression; Medical consultation; Gender; Age
1. Introduction Major depressive disorder (MDD) is a common psychiatric disorder and is an important cause of disability. In North America and Western Europe, it was estimated that between 2% and 6% of the adult general population had a MDD in the previous year or in the previous *
Corresponding author. Tel.: +1 650 494 1137; fax: +1 650 947 9813/650 493 1225. E-mail address: [email protected] (M.M. Ohayon). 0022-3956/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jpsychires.2005.02.003
month (Blazer et al., 1994; Dunlop et al., 2003; Jonas et al., 2003; Kessler et al., 2003; Meltzer et al., 1995; Ohayon et al., 1999a,b; Ohayon and Schatzberg, 2003; Regier et al., 1988; Weissman et al., 1996). Information on the prevalence of MDD in the general population of Asian countries is relatively scant and MDD was consistently reported to be lower than that observed in North America and Western Europe. Early estimates using DSM-III criteria set the lifetime prevalence between 0.9% and 3.4% in Hong Kong (China), Seoul (South Korea) and Taiwan (Chen et al., 1993;
M.M. Ohayon, S.-C. Hong / Journal of Psychiatric Research 40 (2006) 30–36
Hwu et al., 1989; Lee et al., 1990). More recently, a Japanese community survey (Gifu city) using the UM-CIDI reported a 6-month MDD prevalence of 1.2% and a lifetime MDD prevalence of 2.9% (Kawakami et al., 2004). This study aims to assess the point prevalence of DSM-IV MDD in the general population of Korea and the risk factors associated with MDD.
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The participation rate was 91.4% (3719 completed interviews from 4067 eligible households) and the response rate was 86.1% (3719 completed interviews from 4321 contacted households). The final sample was composed of 3719 South Koreans representative of the targeted population. 2.2. Interviews
2. Methods 2.1. Sample The study has conducted between April and July 2001. The target population was non-institutionalized South Koreans aged 15 years or older. This represented 37,364,511 inhabitants. In 2001, 91.8% of South Korean households have the telephone and 79.4% had at least one cellular telephone according to the Korean National Statistical Office (www.nso.go.kr/eng/). A two-stage sampling design was used to draw the sample: In the first stage, a random sample of telephone numbers was drawn based upon the population distribution within the 16 provinces (Do) of South Korea and their counties (Gu). Inside each province, telephone numbers were randomly picked with respect to the size of the counties. In the second stage, during the initial telephone contact, the Kish sampling procedure (Kish, 1965) was used to select a household member. This method allows a random selection that maintains a representative sample in terms of age and gender and limits non-coverage error. The interviewer collected the age and gender of all eligible household members. The Sleep–EVAL system sorted the men and then the women by decreasing age and identified the person to interview based on one of the eight selection tables created by Kish. Each telephone number was assigned with one of the Kish tables. Individuals who did not speak Korean fluently, who suffered from hearing or speech impairment or an illness that precluded being interviewed were excluded from the study. Subjects who declined to participate or who gave up before completing half the interview were classified as refusals even though they might have met an exclusion criterion. Phone numbers were dialed at least 10 times at different times of the evening and on different days, including weekends, before being replaced. Overall, 8882 telephone numbers were used: 54% were rejected because it was a business, a fax or a number not in service (94.7%) and 254 potential participants had an exclusion criterion (97 had a speech or hearing impairment; 7 did not speak Korean; 36 were too ill to be interviewed and 114 had other limitations).
Interviews were conducted from 12 computer terminals located at St.VincentÕs Hospital (Kyunggi Do, South Korea). Interviewers inexperienced in psychiatric diagnosis but specially trained to use the Sleep–EVAL knowledge-based system performed the interviews. Their training lasted approximately 6 h. The training consisted mainly of role-playing, during which the interviewers practiced how to introduce the study and how to ask the questions and enter the answers on the computer. They were instructed to read the questions as they appeared on the monitor screen, to read all the answer choices and to never decide for the participant what was the most appropriate answer. Interviews lasted on average 37.08 (±20.12) min with a median of 32 min. The longest interviews involved subjects with sleep disorders associated with mental disorders. Interviews could be split over two or more sessions if the duration exceeded 60 min. Participants answered on average 233 (±67.84) questions (range: 66–464 questions). 2.3. Instrument Interviewers used the Sleep–EVAL knowledge-based expert system, (Ohayon, 1999, 1995a,b) to conduct the interviews on sleep and mental disorders. This computer system is specially designed to administer questionnaires and conduct epidemiological studies in the general population. The questionnaire was translated from the English version to the Korean version and then backs again into English language to ensure the questions kept the same meaning. The interviews began with a standard questionnaire seeking sociodemographic information, the sleep/wake schedule and the physical health status. Questions related to sleep and mental disease symptoms were also asked. Answers to these questions were used by the system to select a series of plausible diagnostic hypotheses (causal reasoning process). Each hypothesis was investigated with further questioning and deductions of the consequences of each answer. This process allowed the system to confirm or reject these hypotheses (nonmonotonic, level-2 feature). The system contained all questions required for entire diagnostic descriptions according to the International Classification of Sleep Disorders (ASDA, 1997) and the Diagnostic and
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Statistical Manual of Mental Disorders, fourth edition (DSM-IV) (APA, 1994) classifications. The differential diagnosis process was based on a series of key rules allowing or prohibiting the co-occurrence of two diagnoses in accordance with ICSD and DSM-IV prescriptions. The interview ended once all diagnostic possibilities were exhausted. The system has been tested in various contexts: in clinical psychiatry and sleep disorders clinics. In psychiatry, the first study found overall kappas among the diagnoses of four psychiatrists and those of the system ranged from 0.44 with one psychiatrist to 0.78 with two psychiatrists (n = 114 cases) (Ohayon, 1995a,b). Kappa for major depressive disorder was 0.82 and kappa for bipolar disorder was 0.77. Overall kappa between psychiatrists and the system was 0.71 (Ohayon, 1995a,b). In another study that involved 91 forensic patients, most of the patients (60%) met criteria for a diagnosis in the psychosis spectrum. The kappa between diagnoses obtained by the system and those given by psychiatrists was 0.44 for specific psychotic disorders (mainly schizophrenia) (St-Onge and Ohayon, 1994). Other validation studies were also conducted specifically for sleep disorders (Hosn et al., 2000; Ohayon et al., 1999a,b).
This series of questions permitted evaluation of DSMIV criteria for a diagnosis of major depressive episode. 2.5. Statistical analyses Data were weighted to compensate for disparities between the final sample and the data of the official Korean census. Bivariate analyses involving categorical or qualitative variables were carried out with v2 statistics. Risk factors associated with MDD were analyzed using logistic regression (Hosmer and Lemeshow, 1989). Ninety-five percent confidence intervals were calculated for prevalence rates and odds ratios. Reported differences were significant at 0.05 or less.
3. Results The final sample is composed of 3719 subjects aged from 15 to 90 years old. Men composed 49.5% of the weighted sample (n = 1,842). Most subjects were married (63.7%) or single (32.9%). Separated or divorced participants represented less than 1% (0.2%) and widowed accounted for 3.2% of the sample. Subjects living in the metropolitan area of Seoul represented 22.6% of the sample.
2.4. Variables 3.1. Prevalence of depressive mood Information was collected about: sociodemographic information (age, gender, marital status, education, occupation), use of alcohol, tobacco, caffeine (quantity per day), health care utilization, current physical health status (presence of illnesses and perceived health quality), perceived level of stress, and social network. Depression was investigated with questions assessing: (1) if the subject was feeling sad, downcast or depressive; (2) feelings of hopelessness; (3) if the subject had lost interest and lacked pleasure in activities formerly considered pleasant. These questions were answered on an intensity scale (extremely, a lot, moderately, slightly, not at all, does not know), and then for each symptom whether it was present most of the day and nearly every day. Positive answers on one of these three questions triggered another series of questions that assessed: (1) changes in appetite or weight; (2) insomnia or hypersomnia symptoms (obtained with the help of the sleep questionnaire and supplemental questions to evaluate their appurtenance to depressive illness); (3) psychomotor agitation or retardation; (4) fatigue or loss of energy; (5) feelings of worthlessness or guilt; (6) difficulties in concentration or thinking, difficulties making decisions; (7) suicidal ideations. All these were rated by the subjects on the intensity scale used for the initial symptoms alone, as well as whether the symptom was present most of the day and nearly every day. The subjects also reported how long they experienced a depressive mood.
A total of 20.9% (95% confidence interval: 19.6– 22.2%) of the sample reported feeling sad, downcast, having the blues or having lost interest in things formerly pleasant at the time of the interview. The prevalence was comparable between men (20.4%) and women (21.5%) and among the six age groups. 3.2. Prevalence of major depressive disorders Major depressive disorders (MDD) were found in 3.6% (95% CI: 3.0–4.2%) of the sample (point prevalence). The prevalence was comparable between men and women and among age groups (Table 1). Similarly, marital status and level of education were not associated with MDD. A higher prevalence of MDD was found in shift/night workers compared to daytime workers. Similarly, individuals living in Seoul metropolitan city, Kyeongsangnam, Kyongsangbuk or Chungchongnam provinces were more likely to have a MDD than those living in the Kwangju, Kangwon and Chollabuk provinces (Table 1). A major depressive episode lasted on average 32 weeks. 3.3. Factors associated with major depressive disorders A logistic regression was performed to identify factors associated with MDD. Variables entered in the
M.M. Ohayon, S.-C. Hong / Journal of Psychiatric Research 40 (2006) 30–36 Table 1 Point prevalence of major depressive disorders by sociodemographic characteristics
Gender Male Female Age groups (yrs) 15–24 25–34 35–44 45–54 55–64 >=65
N
Prevalence
95%CI
1842 1877
3.2 4.0
[2.4–4.0] [3.2–4.9]
779 899 841 500 386 313
3.8 3.1 4.2 4.1 2.1 4.6
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Table 2 Factors associated with major depressive disorders – multiple logistic regression model Prevalence of Adjusted MDD
ORa
95%CI
Sig.
Gender Male Female
3.2 4.0
1.00 1.59
[0.96–2.63]
0.07 n.s.
[2.4–5.1] [2.0–4.2] [2.8–5.5] [2.3–5.8] [0.7–3.6] [2.3–7.0]
Occupation Daytime work Shift/night work Not working Student
2.4 6.5 3.7 3.6
1.00 1.89 1.40 1.79
[0.99–3.61] [0.79–2.48] [0.72–4.47]
0.055 n.s. n.s. n.s.
1.00 1.92 0.76 4.48
[1.06–3.48] [0.33–1.78] [1.42–14.12]
0.031 n.s. 0.011
Marital status Not Married Married
1335 2345
4.3 3.3
[3.2–5.4] [2.6–4.1]
Education Never went to school <11 yrs schooling 12 yrs schooling Non-university grade Some university
Number cigarettes per day Non-smoker 3.2 <15 5.7 15–24 2.9 >=25 16.4
222 676 1110 938 732
3.4 4.4 3.2 3.5 4.0
[1.0–5.9] [2.9–6.0] [2.2–4.2] [2.4–4.7] [2.6–5.4]
Level of stress Low Moderate High
1.5 4.8 14.6
1.00 2.68 7.40
[1.65–4.35] [4.50–12.16]
0.001 0.001
Health status Good Average Poor
2.0 7.6 19.6
1.00 2.40 7.17
[1.52–3.77] [3.99–12.88]
0.001 0.001
Number of medical consultations last year None 1.00 1 1.11 >=2 1.62
[0.42–2.93] [0.99–2.64]
n.s. 0.054
Physical activities No physical activity Daytime Evening
[0.54–1.29] [1.03–3.19]
n.s. 0.04
[1.63–4.86]
0.001
[0.56–2.13] [0.10–7.54]
n.s. n.s.
Occupation Daytime work Shift/night work Not working Student Areas Seoul metropolitan city Kuonggi province Pusan metropolitan city Kyeongsangnam province Daegu metropolitan city Inchon metropolitan city Kyongsangbuk province Chollanam province Chollabuk province Chungchongnam province Kangwon province Chungchongbuk province Kwangju metropolitan city Daejon metropolitan city Ulsan metropolitan city Chdju province a b c
992 420 1570 737
2.4 6.5a 3.7 3.6
[1.5–3.4] [4.1–8.9] [2.8–4.6] [2.2–4.9]
844 693 288 230 198 197 186 171 161 155 134 125 113 108 77 39
4.8b 2.7 3.4 8.3b 2.5 3.7 5.8c 1.5 0.9 7.5b 0.6 2.7 0.3 2.6 0.9 2.0
[3.4–6.3] [1.5–3.9] [1.3–5.6] [4.7–11.9] [0.3–4.7] [1.0–6.3] [2.4–9.1] [0.0–3.4] [0.0–2.4] [3.3–11.7] [0.0–2.0] [0.0–5.5] [0.0–1.2] [0.0–5.6] [0.0–3.0] [0.0–6.6]
p < 0.01 With daytime work. p < 0.01 With Kwangju, Kangwon, Chollabuk and Ulsan. p < 0.05 With Kwangju, Kangwon and Chollabuk.
model were: age, gender, marital status, education level, occupation, geographic areas, BMI, number of glasses of alcohol per day, number of cigarettes per day, number of cups of coffee/tea per day, perceived health status, number of medical consultations in the previous year, presence of physical disease, perceived stress, and level of satisfaction with the social network. Significant variables associated with MDD are presented in Table 2. These variables were being a light or heavy smoker, perceiving oneÕs health as being average or poor, doing physical activities at least three times
3.4 3.2 7.0
1.00 0.84 1.81
Body mass index (kg/m2) <18.5 8.2 18.5–24.9 3.2 25–29.9 3.3 >= 30 2.6
2.81 1.00 1.10 0.85
Non-significant variables were age, geographic areas, coffee intake, alcohol intake, level of satisfaction with social life. a Model adjusted for effect of one on each other variable.
per week in the evening, having a BMI below 18.5 kg/m2 and perceiving oneÕs life as being moderately or highly stressful. Being a shift or night worker and having consulted at least two times a physician in the previous year were marginally significant. 3.4. Medical consultations and treatment Only 15.7% of the sample had consulted a physician in the previous 12 months. MDD subjects were more likely to have consulted (31.9%) than the remaining individuals of the sample (15.1%; p<0.0001). However, consultation for depressive mood was very low: only 2.2% of MDD subjects reported that depressive mood was a
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motive for consultation. Antidepressant treatment was also infrequent: only 7.4% of MDD subjects were currently taking this type of treatment.
4. Discussion This epidemiological study is the first to assess the prevalence of major depressive disorder in Korea in nearly two decades and is the first nationwide South Korean study to use DSM-IV criteria. A nationwide study was performed in 1995 but was limited to depressive symptoms assessed with the CES-D (Cho et al., 1998). We found the point prevalence of major depressive disorder to be 3.6%, which is higher than what was reported earlier in Korea: The study of Lee et al., conducted in 1984 (Lee et al., 1990) reported a 12-month prevalence of 2.3% and a lifetime prevalence of 3.4%. It is also higher than the prevalence reported in other Asian countries. For example, the WHO consortium (Demyttenaere et al., 2004) reported a 12-month prevalence of mood disorders at 2.5% in Beijing (China) and 1.7% in Shangai (China). However, China is a developing country while South Korea is an industrialized country, with 60% of the households with at least one computer and 75.4% with Internet access. In Japan, Kawakami et al. (2004) reported a 6-month prevalence of MDD at 1.2%. However, in that study, the participation rate was low (56.9%) and it was done in a mediumsize city (Gifu city) of 410,036 inhabitants. In our study, we also found a lower rate of MDD in smaller cities and provinces. Our rate, however, is lower than the prevalence found in recent North American studies: a 30-day prevalence of 4.9% (Blazer et al., 1994) and a 12-month prevalence of 6.6% (Kessler et al., 2003). Our rate is lower than or comparable to prevalences observed in Western European countries (Andrade et al., 2003; Ayuso-Mateos et al., 2001; Ohayon et al., 1999a,b). For example, the ESEMeD study using the CIDI and including six European countries (Italy, Spain, the Netherlands, Belgium, France and Germany) reported a 12-month prevalence of MDD at 3.9% (Alonso et al., 2004). However, this study also had low participation rates in four of the six countries surveyed (45.9–57.8%). Using the same tool as in this study, Ohayon and Schatzberg (2003) found a prevalence of MDD at 4.0% in their European sample of 18,980 subjects. We did not find significant changes associated with gender and age as reported in many North American or European studies. This lack of association is not unique to our study and was also reported in other Asian studies (Kawakami et al., 2004; Weissman et al., 1996). The comparison with other studies is obviously complicated by the fact that we did not use the WHO-CIDI or its variants. The structure of the Sleep–EVAL ques-
tionnaire, however, is similar to that of the CIDI in the sense that the evaluation of MDD began with a series of three questions on current depressive mood and loss of interest and pleasure. Negative answers to these questions stopped the exploration of depressive disorders. There is also the possibility that the method of answering the questions influenced the prevalence. In the CIDI, questions are answered by ‘‘yes’’ or ‘‘no.’’ In the Sleep–EVAL system, questions are mostly answered on scales (frequency, severity or modulated yes/no, for example, rather yes or rather no). As stressed by Noh and Chen (1998, 1992) and Jang et al. (2001), Korean individuals are sensitive to response style. For example, while it is all right for an American or a European to affirm he is happy with his life, it is not socially acceptable to do so for a Korean. Therefore, there is the possibility that the direct approach of the Western way to assess mental disorders is less appropriate and less effective with Asian people. However, more crosscultural research is still needed to improve our understanding of cultural differences in the assessment of mental disorders. Our presentation of the study to the participants was also different; the first aim of our study was to investigate sleep disorders in the population and was presented as such to the participants. The first half of the interview was used to collect information on sleep habits, sleep disturbances, health and health care utilization. Questions about mental health issues appeared later in the interview; this may have helped to alleviate the stigma associated with psychiatric disorders. While the majority of South Korean households have a telephone (91.8%) or a cellular phone (79.4%), the rate is lower in the poorest households: In households earning less than 12,000 USD per year, 85.3% had a telephone and 51.5% had a cellular telephone. Therefore, there is a chance that we have under-sampled the poorest households. The South Korean society has undergone several changes in the past three decades. The rapid economic growth and industrialization of the country are likely to have had a harder effect on some segments of the population, such as the elderly, for whom a social security system is nearly non-existent. Once they reach the age of retirement, the Korean elderly often have to rely on family support or are living in poverty. This could partly explain why we found a high rate of MDD (4.6%) in subjects 65 years or older, while in Western countries the prevalence of MDD decreases with age (Andrade et al., 2003; Kessler et al., 2003). Similarly, shift/night work, dissatisfaction with work and stressful life were associated with a high prevalence of MDD in our sample (respectively, 6.5%, 9.7% and 14.6%). Shift and night work as well as poor job satisfaction have been proven to be associated with poor mental health status in sev-
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eral studies (Bildt and Michelsen, 2002; Shigemi et al., 1997) and to the development of depression (Bildt and Michelsen, 2002). Association between MDD and physical exercise in the evening was mostly due to shift and night work: we found that 22.2% of shift and night workers who exercised in evening had a MDD. The percentage of the sample that consulted a physician is very low in our sample even though Korea has national health insurance with universal coverage of the population. Until July 2000, there was no separation of drug prescription and dispensing: Both physicians and pharmacists prescribed and dispensed drugs. Many people see a pharmacist initially for minor health problems. Therefore, pharmacists often act as a first-line health-care provider. A direct consequence of this practice was that few subjects with a MDD consulted a physician and fewer had an appropriate treatment for their depressive disorder. This situation is not unique to Korea; even in countries where drug prescription is made solely by physicians, a sizeable number of patients with major depressive disorder go undetected and remain untreated. In conclusion, new research directions are needed in this field: Comparison with other Asian countries, family studies, impact of pain on depression are of interest. Characterizing the specificity of depression symptomatology in comparison to Western countries could be a way to find invariant factors and patterns of depression across cultures.
Acknowledgment This study was supported by unrestricted educational grants from Lilly-Korea and Sanofi-Synthelabo Korea.
References Alonso J, Angermeyer MC, Bernert S, Bruffaerts R, Brugha TS, Bryson H, et al. ESEMeD/MHEDEA2000 investigators, European study of the epidemiology of mental disorders (ESEMeD) project. 12-month comorbidity patterns and associated factors in Europe: results from the European study of the epidemiology of mental disorders (ESEMeD) project. Acta Psychiatrica Scandinavica Suppl 2004(420):28–37. Andrade L, Caraveo-Anduaga JJ, Berglund P, Bijl RV, De Graaf R, Vollebergh W, Dragomirecka E, Kohn R, Keller M, Kessler RC, Kawakami N, Kilic C, Offord D, Ustun TB, Wittchen HU. The epidemiology of major depressive episodes: results from the International Consortium of Psychiatric Epidemiology (ICPE) Surveys. International Journal of Methods in Psychiatric Research 2003;12:3–21. American Psychiatric Association (APA). Diagnostic and statistical manual of mental disorders. fourth ed. Washington: The American Psychiatric Association; 1994. Ayuso-Mateos JL, Vazquez-Barquero JL, Dowrick C, Lehtinen V, Dalgard OS, Casey P, Wilkinson C, Lasa L, Page H, Dunn G, Wilkinson GODIN Group. Depressive disorders in Europe:
35
prevalence figures from the ODIN study. British Journal of Psychiatry 2001;179:308–16. Bildt C, Michelsen H. Gender differences in the effects from working conditions on mental health: a 4-year follow-up. International Archives of Occupational and Environmental Health 2002;75:252–8. Blazer DG, Kessler RC, McGonagle KA, Swartz MS. The prevalence and distribution of major depression in a national community sample: the National Comorbidity Survey. American Journal of Psychiatry 1994;151:979–86. Chen CN, Wong J, Lee N, Chan-Ho Lau J, Fung M. The Shatin Community Mental Health Survey in Hong Kong. II. Major findings. Archives of General Psychiatry 1993;50:125–33. Cho MJ, Nam JJ, Suh GH. Prevalence of symptoms of depression in a nationwide sample of Korean adults. Psychiatry Research 1998;81:341–52. Demyttenaere K, Bruffaerts R, Posada-Villa J, Gasquet I, Kovess V, Lepine JP, et al. WHO World Mental Health Survey Consortium. Prevalence, severity, and unmet need for treatment of mental disorders in the World Health Organization World Mental Health Surveys. JAMA 2004;291(21):2581–90. Dunlop DD, Song J, Lyons JS, Manheim LM, Chang RW. Racial/ ethnic differences in rates of depression among preretirement adults. American Journal of Public Health 2003;93:1945–52. Hosmer DW, Lemeshow S. Applied logistic regression. New-York: Wiley; 1989. Hosn R, Shapiro CM, Ohayon MM. Diagnostic concordance between sleep specialists and the Sleep–EVAL system in routine clinical evaluations. Abstract Journal of Sleep Research 2000;9(Suppl. 1): 86. Hwu HG, Yeh EK, Chang LY. Prevalence of psychiatric disorders in Taiwan defined by the Chinese diagnostic interview schedule. Acta Psychiatrica Scandinavica 1989;79:136–47. ICSD – International Classification of Sleep Disorders: Diagnostic and Coding Manual (ICSD). Rochester and Minnesota: American Sleep Disorders Association; 1997. Jang Y, Small BJ, Haley WE. Cross-cultural comparability of the geriatric depression scale: comparison between older Koreans and older Americans. Aging and Mental Health 2001;5:31–7. Jonas BS, Brody D, Roper M, Narrow WE. Prevalence of mood disorders in a national sample of young American adults. Social Psychiatry and Psychiatric Epidemiology 2003;38:618–24. Kawakami N, Shimizu H, Haratani T, Iwata N, Kitamura T. Lifetime and 6-month prevalence of DSM-III-R psychiatric disorders in an urban community in Japan. Psychiatry Research 2004;121:293–301. Kessler RC, Berglund P, Demler O, Jin R, Koretz D, Merikangas KR, Rush AJ, Walters EE, Wang PS. The epidemiology of major depressive disorder: results from the National Comorbidity Survey Replication (NCS-R). JAMA 2003;289:3095–105. Kish L. Survey sampling. New York: Wiley; 1965. Lee CK, Kwak YS, Yamamoto J, Rhee H, Kim YS, Han JH, Choi JO, Lee YH. Psychiatric epidemiology in Korea. Part I: gender and age differences in Seoul. Journal of Nervous and Mental Disease 1990;178:242–6. Meltzer H, Gill B, Petticrew M, Hinds K. The prevalence of psychiatric morbidity among adults living in private households. OPCS Surveys of Psychiatric Morbidity in Great Britain: Report 1. London: HMSO; 1995. Noh S, Chen X. Measuring depression in Korean immigrants: assessing validity of the translated Korean version of CES-D scale. Cross-cultural Research 1998;82:358–77. Noh S, Avison W, Kaspar V. Depressive symptoms among Korean immigrants: assessment of a translation of the CES-D. Psychological Assessment 1992;4:84–91.
36
M.M. Ohayon, S.-C. Hong / Journal of Psychiatric Research 40 (2006) 30–36
Ohayon M. Knowledge based system Sleep–EVAL: decisional trees and questionnaires. Ottawa: National Library of Canada; 1995a. Ohayon M. Validation of expert systems: examples and considerations. Medinfo 1995b;8:1071–5. Ohayon M. Improving decision making processes with the fuzzy logic approach in the epidemiology of sleep disorders. Journal of Psychosomatic Research 1999;47:297–311. Ohayon MM, Guilleminault C, Zulley J, Palombini L, Raab H. Validation of the Sleep–EVAL system against clinical assessments of sleep disorders and polysomnographic data. Sleep 1999a;22:925–30. Ohayon MM, Priest RG, Guilleminault C, Caulet M. The prevalence of depressive disorders in the United Kingdom. Biological Psychiatry 1999b;45:300–7. Ohayon MM, Schatzberg AF. Using chronic pain to predict depressive morbidity in the general population. Archives of General Psychiatry 2003;60:39–47.
Regier DA, Boyd JH, Burke Jr JD, Rae DS, Myers JK, Kramer M, Robins LN, George LK, Karno M, Locke BZ. One-month prevalence of mental disorders in the United States: based on five epidemiologic catchment area sites. Archives of General Psychiatry 1988;45:977–86. Shigemi J, Mino Y, Tsuda T, Babazono A, Aoyama H. The relationship between job stress and mental health at work. Industrial Health 1997;35:29–35. St-Onge B, Ohayon M. LÕutilisation du syste`me Expertal dans un milieu de psychiatrie le´gale. Abre´ge´s du Congre`s de Psychiatrie et de Neurologie de Langue Franc¸aise 1994:112. Weissman MM, Bland RC, Canino GJ, Faravelli C, Greenwald S, Hwu HG, Joyce PR, Karam EG, Lee CK, Lellouch J, Lepine JP, Newman SC, Rubio-Stipec M, Wells JE, Wickramaratne PJ, Wittchen H, Yeh EK. Cross-national epidemiology of major depression and bipolar disorder. JAMA 1996;276(4):293–9.