Previous work has strongly supported the idea that childhood and adolescent psychopathology are predictive of poor adjustment and psychopathology in adulthood (1, 2). Knowledge about the magnitude, expression, and course of psychiatric illness among children and adolescents is therefore important. Regarding prevalence, previous studies using psychiatric interviews reported that the rates of all disorders varied from 4.6% (3) to 50.4% (4), with an overall rate of around 20% (5, 6). Recent surveys have generally applied the two-stage design (5, 7, 9) and included the assessment of impairment in the case definition, according to the requirement in DSM-III-R and DSM-IV (4, 7, 8).
Prevalence rates for attention deficit hyperactivity disorder (ADHD), specific phobia, social phobia, and separation anxiety disorder were in the range of 3%–10% (10, 11), 0.3%–21.6% (8, 12), 0.2%–9.3% (13, 14), and 0.2%–7.2% (12, 13), respectively. These childhood-onset disorders were reported to decline in rates over time during adolescence (15, 16). Conversely, the rates for conduct disorder/oppositional defiant disorder (3%–5%), substance use disorders, major depression (1.3%–7.0%), and dysthymia (0.4%–8.0%) were found to increase with age during adolescence (8, 17, 18). The magnitudes of conduct disorder/oppositional defiant disorder and substance use disorders have differed considerably across countries and ethnicity (19, 20).
Like many other countries, youths in Taiwan today are facing greater familial-socioenvironmental stress than their predecessors. Owing to the rigid educational system and high parental expectation on academic achievement, the competition in joint entrance examinations for senior high schools (grades 10–12) and universities is very keen (21). Following globalization in trade, the restriction of imported duty on alcohol and tobacco has been lessened, with increased consumption in recent years (22). Moreover, betel has become more available in Taiwan in the past decade because of markedly increased commercial interest (23). These environmental changes and their impact on adolescent psychopathology deserve an adequate inquiry. Therefore, an epidemiological study of mental disorders in adolescents was conducted in Taiwan.
This project consisted of a cross-sectional and a longitudinal survey. The cross-sectional survey was conducted among 774 ninth-grade students in 1994–1995, focusing on substance use disorders (9). The two-stage case finding strategy was applied with a brief screening tool for any substance use disorders and the Chinese version of the Schedule for Affective Disorders and Schizophrenia for School-Age Children—Epidemiologic Version (K-SADS-E) (9, 24, 25). The lifetime weighted prevalence rate of any DSM-III-R substance use disorder was 11.0% and was significantly higher in boys, in a rural community, and in classes with poor academic performance (9). A 3-year panel study was then carried out to investigate the prevalence and trend of psychiatric disorders in 1995–1997. This article reports the research methods, prevalence rates of specific mental disorders, and their changing trends in relation to gender and urban or rural settings across the 3 years.
This was a school-based panel study among a sample of seventh-grade students established in the first year of the survey.
Eighteen of 34 classes and eight of 10 classes in grade 7 were randomly selected from one urban and one rural junior high school in South Taiwan, respectively. The two schools were selected based on the positive response and cooperativeness of their principals. The former represented a typical urban school with a high pass rate in the joint entrance examination for senior high school; the latter represented a typical rural school with a low pass rate in such an examination over the years. All the students in the selected classes were included in the study sample. The study sample consisted of 1,070 students (532 boys and 538 girls, ages 13–15), in which 725 (67.8%) were from urban areas (357 boys and 368 girls) and 345 (32.2%) were from rural areas (175 boys and 170 girls). The follow-up rates were 98.2% (N=1,051) and 96.7% (N=1,035) in the second year (eighth grade) and the third year (ninth grade), respectively. No significant differences in gender and urban-rural distribution were found between the respondents and the nonrespondents.
The K-SADS-E is a semistructured clinical interview for the systematic assessment of both past and current episodes of mental disorders in children and adolescents (24). Development of the Chinese version of the K-SADS-E was carried out by the Child Psychiatry Research Group in Taiwan (25), which included a two-stage translation and modification of several items with psycholinguistic equivalents relevant to Taiwanese culture. Further modification to meet the DSM-IV diagnostic criteria and an additional section developed for betel use disorder were performed by the research team (9). In this panel study, all the screening items in individual sections of the Chinese K-SADS-E were grouped together to form a separate screening version for use in the first stage of case finding.
The interrater reliability of the Chinese K-SADS-E was examined before administration of the cross-sectional survey among nine consultant child psychiatrists in the research team, and the results showed generalized kappa coefficients ranging from 0.73 to 0.96 for all mental disorders included in the Chinese K-SADS-E. Validity of the screening version of the Chinese K-SADS-E was assessed before the administration of this panel study among 124 randomly selected eighth-grade students. The screening interview was first carried out by 14 psychiatric clinical staff members (nurses, psychologists, social workers, and psychiatric residents), who were instructed to record the presence/absence of all the screening items entirely, according to the response from the study subjects without any personal judgment. Based on the Chinese K-SADS-E interview, the nine consultant child psychiatrists then made psychiatric diagnoses. The subjects with a positive response to any of the Chinese K-SADS-E screening items were treated as screened positive. In this pretest, the overall sensitivity and specificity of the screening interview against any Chinese K-SADS-E diagnostic category were calculated to be 78% and 98%, respectively.
Teacher report form of the Child Behavior Checklist
The Chinese version of the teacher report fform of the Child Behavior Checklist has been proved to be a reliable and valid instrument when used in Taiwanese adolescent populations (26).
The Review Board of the Department of Health, Taiwan, approved this study as ethical for studying adolescents. Child assent and oral informed consent were obtained from the study subjects and their parents, respectively, after detailed explanation of the purpose and interview procedures of this study, and confidentiality about interview records was ensured. The fieldwork was then conducted at school following a timetable arranged by tutors of the study classes.
The same threshold used in the pretest for the first-stage screening was employed in the main survey. In the second stage, all of those who were screened positive and every 1 in 10 who was randomly selected from those who were screened negative were immediately given the second-stage Chinese K-SADS-E interview, conducted by child psychiatrists who were blind to the screening results. There was no time lag between the first- and second-stage interviews, and none of the respondents who received the screening interview refused to take the diagnostic interview. The same two-stage case-finding procedure was conducted in the next 2 consecutive years. Teacher report forms were collected soon after the fieldwork.
A psychiatric diagnosis of the study subjects was first made by child psychiatrists who conducted the Chinese K-SADS-E interview according to the DSM-IV. These diagnoses were then independently reassessed by two senior psychiatrists (S.S.F.G. and A.T.A.C.) by a systematic review of all the interview records. In our reassessment, the principle of rate-down was employed, and any information that was dubious or uncertain was discarded. Psychiatric diagnoses generated from this reassessment were jointly discussed, and our consensus diagnosis was taken as final. To minimize the likely underreporting of externalized disorders by the study subjects, information regarding behavioral syndromes gathered from the teacher report forms was incorporated into our diagnostic consideration for the best estimation of ADHD, oppositional defiant disorder, and conduct disorder.
Statistical analyses were performed with SAS, version 8.2 (SAS Institute, Cary, N.C.). The preselected alpha value was 0.05. The 3-month weighted prevalence rates and their variance for individual psychiatric disorders were calculated with the formula
where p was the weighted prevalence, π was the proportion of the sample screened positive, 1–π was the proportion of the sample screened negative, ƒ was the fraction of the sample screened negative who were interviewed at the second stage, λ1 was the proportion of cases among the sample screened positive who were interviewed, and λ2 was the proportion of cases among the sample screened negative who were interviewed (27). The 95% confidence interval for weighted prevalence was also calculated.
The Cochran-Armitage test for trend with z statistics was used to examine the difference in rates across the three time points. The exact p value was calculated for the test for trend when the sample size of any of the cells in the two-by-three contingency table was less than 5. Chi-square tests or Fisher’s exact test (when the cell number was less than 5) was used to examine the gender and the urban-rural difference. Mantel-Haenszel odds ratios and the corresponding confidence intervals (CIs) were calculated. When the number of any cell of the two-by-two contingency table was less than 5, exact CIs were computed for odds ratios.
Prevalence of Psychiatric Disorders
t1 shows the DSM-IV diagnostic distribution of all panel respondents from seventh to ninth grade with weighted 3-month prevalence rates and their 95% CIs. The overall rates for the seventh and eighth grades were higher than that for the ninth, with a significant decline in trend. Such decline was mainly observed for disruptive behavioral disorders and anxiety disorders, specifically among child-onset disorders (including ADHD, specific phobia, social phobia, and separation anxiety disorder). No such trend was observed for conduct disorder and oppositional defiant disorder. Both depressive disorders (notably major depression) and substance use disorders conversely increased across the three grades. Moreover, the increasing trend was significant, mainly for comorbid substance use disorders and not for any single substance use disorder.
In grades 7 and 8, the most prevalent diagnostic group was disruptive behavioral disorders (notably ADHD), followed by anxiety disorders (notably specific phobia), and substance use disorders. In grade 9, although disruptive behavioral disorders was still ahead of others, the rate for substance use disorders increased to become the second leading disorder, and depressive disorders (mainly major depression) increased to become third. Rates for the top three disorders in grade 9 were, in fact, close to each other. In all three grades, the most common substance of abuse/dependence was nicotine, followed by betel and alcohol.
Disruptive behavioral disorders (mainly conduct disorder and ADHD) and substance use disorders were more prevalent in boys than in girls, whereas the reverse was observed for depressive disorders across the 3 years (t2). Girls had higher rates of anxiety disorders and adjustment disorder than boys, particularly, higher rates of specific phobia in grade 8 and social phobia in grade 9.
The significant changing trends in this panel for most mental disorders over the 3 years were observed in boys and girls. However, the increasing trend for all substance use disorders was only significant in boys. The declined trend for social phobia was only significant in boys and that for adjustment disorder was only significant in girls.
The overall rates of mental disorders were generally higher in rural than in urban youths (t3). Compared to their urban counterparts, rural adolescents had significantly higher rates for conduct disorder, oppositional defiant disorder, and substance use disorders over the 3 years. In grade 9, specific phobia was more prevalent among rural adolescents; in contrast, social phobia was more common among urban adolescents. There was no urban-rural difference in rates for depressive and other anxiety disorders in all grades.
The time trends for most disorders in rural and urban areas also followed those in the total sample, with some exceptions. The increasing trend for all substance use disorders was significant in rural areas but was less apparent in urban areas and only significant for nicotine use disorders. The declining trend for social phobia was only significant among rural adolescents and that for specific phobia was greater in urban than in rural areas, notably in grade 9.
As one of the few studies (1, 8, 28) that have investigated the prevalence and the time trend for adolescent psychiatric morbidities, the present study provided a unique opportunity to compare the sex and the urban-rural difference of such morbidities between developing and developed countries. Our study has employed the two-stage design, and all the clinical interviews were conducted by child mental health professionals with the standardized Chinese K-SADS-E with cross-cultural validation and acceptable interrater reliability. Consensus psychiatric diagnoses were made through independent assessment of the Chinese K-SADS-E interview records and a joint discussion by two senior research psychiatrists. The response rates at phase I and the two follow-ups were very high.
Despite all of these strengths, there are some limitations of this study that require careful consideration in the interpretation of the findings. First, because of a purposeful sampling of study schools, its external validity for other Taiwanese adolescent populations needs to be examined. Second, the psychiatric diagnoses were mainly based on clinical interviews of study subjects without interviewing their parents. Previous studies have shown low agreement among child, parent, and teacher informants in reporting children’s emotional and behavioral problems (29) and the need to incorporate teachers’ reports into the identification of externalizing disorders (29). Therefore, we included the teacher report form to make the best estimates of psychiatric diagnoses of ADHD, conduct disorder, and oppositional defiant disorder. Finally, in this two-stage case-finding study, despite the fact that all the study subjects were screened at the first stage for 3 consecutive years, the second-stage psychiatric interview was not performed among all of them. The lack of complete information in psychiatric diagnoses for all study subjects has prevented us from conducting longitudinal analyses using a multilevel model to examine the trajectories of psychiatric diagnoses at an individual level.
The magnitude of total psychiatric morbidities estimated in this study was in the middle of previous studies (5, 6) and was similar to those (20.9% and 20.3%) of two large-scale epidemiology studies of youths in the United States (4, 8). However, the clinical interview and diagnostic criteria (DSM-III-R) used in those two U.S. studies were different from those in this study. Shaffer et al. (4) employed the National Institute of Mental Health’s Diagnostic Interview Schedule for Children, Version 2.3, and Costello et al. (7) used the Child and Adolescent Psychiatric Assessment.
Although there was only a minor change in the diagnostic criteria for ADHD from DSM-III-R to DSM-IV, the average estimated prevalence of ADHD has been reported to increase from 3%–5% with DSM-III-R to 9%–10% with DSM-IV with the three newly created subtypes (11, 30). The overall prevalence of ADHD in this study was close to the figures in recent studies in Australia (31) with the Diagnostic Interview Schedule for Children and in Brazil (32) with the 18 DSM-IV ADHD symptom items and clinical diagnosis. Similar to findings in previous studies (15), the rates of ADHD declined over adolescence. Our rates of conduct disorder and oppositional defiant disorder were in the lower part of the reported rates across cultures and countries (8, 33), with a nonsignificant increase for conduct disorder over the 3 years in boys.
A unique finding of this study is that unlike Western societies (19), betel instead of alcohol was the second (after nicotine) most prevalent abused substance among our study subjects, which might be attributable to an increased availability of betel because of commercial interest in recent years and the popularity of the betel chewing habit, particularly in rural areas (9). The fact that all the study subjects with substance use disorders had nicotine use disorder and the rates of nicotine dependence had markedly increased over time strongly indicates the seriousness of nicotine damage on health among Taiwanese adolescents today.
The 3-month prevalence rate of depressive disorders in this study was somewhat lower than those in previous studies, which largely reported 6- or 12-month prevalence rates in similar age populations (4, 8). However, our finding of a significant increase in time trend of such morbidity in both sexes was consistent with previous work (20).
Consistent with previous studies, specific phobia was the most common anxiety disorder, followed by social phobia, then generalized anxiety disorder (12–14). The lower trend in the rates of total anxiety disorders mainly came from specific phobia, social phobia, and separation anxiety disorder (16), and girls had a greater stability of internalized disorders than boys over time (34).
Similar to earlier studies, we found higher rates of ADHD, conduct disorder, oppositional defiant disorder, and substance use disorders in boys, contributing to a higher total psychiatric morbidity than girls. Higher rates of anxiety disorders in girls, notably specific phobia and social phobia (35), were also observed. The emerging trend of female excess in depressive disorders at adolescence reported in previous Western surveys (13, 20, 34, 36) was also evident in this study.
Our findings of higher rates of conduct disorder/oppositional defiant disorder and substance use disorders in rural areas, although contrary to that in earlier Western studies (18, 33), were in accordance with those from recent studies in Western (37) and Asian societies (9). The finding of a greater increase in time trend for substance use disorders in rural areas in this study awaits further examination in other societies.
Urban-rural differences in psychiatric morbidity are likely to be associated with multiple social environmental factors. Urban neighborhood as a risk factor for psychiatric disorders has been explained by its close association with lower socioeconomic status in most cities in developed countries (38). This notion might have at least in part explained the higher rates of conduct disorder/oppositional defiant disorder, substance use disorders, and total psychiatric morbidities among adolescents in rural Taiwan, where the socioeconomic status has been generally lower than in their urban counterparts (9, 39). Another important factor for such difference in morbidity in Taiwan may have come from a positive selective migration of the mentally fit from rural to urban cities (39). For example, rural children from the families of higher socioeconomic status move to urban cities for better educational opportunities, leaving behind those who are more socioeconomically disadvantaged and less academically competent, with a higher vulnerability to both psychological disorders and substance abuse (9). In consequence, performance on the Joint Entrance Examination for Senior High School is generally better among urban junior high schools than among their rural counterparts (9).
Findings regarding the relationships between low socioeconomic status and anxiety and mood disorders have been contradictory (8, 35). The present study did not find any significant association between urban or rural residency, a proxy for socioeconomic status, and the rates of ADHD, depressive disorders, and most anxiety disorders. Our finding of different time trends for specific phobia and social phobia across urban or rural residency may deserve further inquiry. It is likely that environmental exposure may last longer for specific phobia in rural areas globally and may be higher regarding the pressure from social contact and school performance in urban areas in developing countries.
Implications for Prevention
It is imperious to provide a protective environment to prevent childhood-onset emotional and behavioral disorders and substance-related disorders among vulnerable adolescents. Our findings have implied that the amelioration of detrimental risk factors in social environment (be it more prevalent in rural or urban settings in different societies) for mental disorders in adolescents may serve as the target for primary prevention. Betel abuse, a specific disorder in Taiwan and certain Asian countries, ought to be prevented among both adolescent and adult populations, especially in rural areas. Further investigation of risk factors, patterns of comorbidity, and the trajectories of psychopathology during adolescence is crucial for the identification of the target for primary prevention among different vulnerable groups.
Received Oct. 1, 2003; revisions received Feb. 18 and May 11, 2004; accepted June 14, 2004. From the Department of Psychiatry, College of Medicine, and the Institute of Preventive Medicine, College of Public Health, National Taiwan University, and National Taiwan University Hospital, Taipei, Taiwan; the Department of Psychiatry, Chang Gung Memorial Hospital and Chang Gung University, Kaohsiung, Taiwan; and the Institute of Biomedical Sciences, Academia Sinica. Address correspondence and reprint requests to Dr. Cheng, Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan; firstname.lastname@example.org (e-mail). Supported by grants from the Taiwan Department of Health (DOH-85-TD-131, DOH-86-TD-104, and DOH-87-TD-1161). The authors thank all the child psychiatric staffs who participated in this study and the Child Psychiatry Research Group in Taiwan, which provided the Chinese Schedule for Affective Disorders and Schizophrenia for School-Age Children—Epidemiologic Version for use in this study.