The Epidemiology of Childhood Psychiatric Disorders: Prevalence Findings from Recent Studies NANCY A. BRANDENBURG , PH.D., ROBERT M. FRIEDMAN, PH.D.,
AND
STARR E. SILVER, PH.D.
Abstract. While sharing a new emphasis upon identifying discrete psychiatric disorders in children and adolescents, epidemiological field studies conducted during the past decade have used diverse ,methods o f case ascertainment and definition. Half used the multimethod-multistage approach to ascertain cases. Severity rating scales and measures of pervasiveness, parent-child concordance, and global functional impairment were employed to enhance the specificity of case definition. The majority of overall prevalence estimates of moderate to severe disorder range from 14 to 20%. Those investigations that use multiple methods to define caseness show greatest promise in identifying true cases in community samples. J. Am ; Acad. Child Adolesc. Psychiatry , 1990,29, 1:7683. Key Words: prevalence, identification of childhood disorder, caseness, multimethod-multistage approach.
The principal aims of descriptive epidemiological studies in child psychiatry are threefold: to estimate the overall prevalence of psychiatric disorder and of the specific disorders that together constitute overall prevalence, to identify correlates of those disorders, and to estimate the absolute number of affected individuals for planning mental health services. The purpose of this review is to present and discuss prevalence estimates of childhood disturbance from community surveys conducted in the past decade--a decade characterized by the development of a formal 'taxonomic system with explicit criteria to operationalize the diagnostic process and the creation of structured interview instruments designed to detect psychiatric disorders in community samples. These studies, through various methods, reflect efforts to enhance specificity in the definition of " caseness."
of clinical maladjustment among U.S. children at 11.8%. Teachers identified children as disturbed in 21 studies conducted before 1970; in four studies conducted during the 1970s, parents served as informants . In addition to using a single informant, these studies were characterized by use of a single method to identify disturbed children and youth . The emergence of a new generation of field studies in child psychiatry reflects two major developments : refinements in case ascertainment and definition that parallel the careful emphasis on design, field methods, and instrumentation exemplified by the NIMH Epidemiology Catchment Area (ECA) program (Eaton .et al. , 1984; Regier et aI., 1984) and, in some studies, application of the multimethodmultistage approach pioneered by British psychiatrist Michael Rutter and colleagues (Rutter et aI. , 1970) in new samples of children and adolescents . Sampling methods, the type of measures employed, and case definition profoundly impact prevalence estimates . These topics will be explored in detail before prevalence estimates from these studies are discussed.
Historical Perspective Past studies of the prevalence of childhood disorders did not describe the frequency of discrete psychiatric conditions in children, but instead reported the occurrence of global conditions such as "maladjustment" or "maladaptation" (Gould et aI., 1980). Based on a review of 25 prevalence studies conducted in the United States between 1928 and 1975, Gould et al. (1980) estimated the median prevalence
Populations and Samples Sampling Methodology and Nonresponse Over the past decade, published reports have described eight prevalence surveys of childhood and adolescent psychiatric disorder conducted in five Western developed nations (Table 1). Surveys have been conducted in Australia (Connell et aI., 1982), Norway (Vikan , 1985), the Netherlands (Verhulst et al., 1985), New Zealand (Anderson et al., 1987), and Canada (Offord et al. , 1987). Populations sampled in the United States include those in Missouri (Kashaniet al., 1987), Upstate New York (Cohen etal. , 1987), and Puerto Rico (Bird et aI. , 1988). Sampling units have included the year of birth, the school , and the household. While these studies have varied in the sophistication of the sampling method employed , most investigators have attempted to achieve representativeness in socioeconomic and/or population density indices. In those studies where schools were the sampling unit, institutionalized children were excluded from the sample (Connell et al., 1982; Kashani et aI., 1987); such children were excluded in the Canadian study as well (Offord et aI., 1987).
Accepted February 13, 1989. Dr. Friedman is Chairp erson and Profess or of Psychology , Departm ent ofEpidemiology and Poli cy Analysis, Florida Mental Health Institute, University of South Florida . Dr . Friedman is also Executive Director, and Dr. Silver is Research Director, Research and Training Center for Children' s Mental Health. Dr. Brandenburg is Assistant Professor ofEpidemiology and Biostatistics, College ofPublic Health , and Research Epidemiologist. This research is supported in part by the Nati onal Institute on Disability and Rehabilitative Research and the National Institute ofMental Health , Grant No . 008435138, and by the Florida Mental Health Institute . The authors thank Victoria Innis and Kris Keller fo r their assistance in manuscript preparation. Reprint requests to Dr. Friedman , Depa rtment ofEpidemiology and Policy Analysis, Florida Mental Health Institute, 13301 Bruce B . Downs Boule vard, Tampa , FL 33612-3899 . 0890·8567/90/290 I-D076$2.00/0© 1990by the American Academy of Child and Adolescent Psychiatry .
76
PREVALENCE OF CHILDHOOD PSYCHIATRIC DISORDERS TABLE
Study
1. Populations Sampled, Methods of Sampling, and Response Rates in Recent Epidemiological Investigations Population Sampled : Survey Dates
Method of Sampling Two-stage sampling of subjects based upon scores on a screening scale Two-stage sampling of subjects based upon scores on a screening scale Two-stage sampling of subjects based upon scores on a screening scale All available members of the birth cohort
79.0
All age-appropriate subjects available for follow-up
75.0
Random sample stratified by age and sex All age-appropriate children within eligible households Two-stage sampling of subjects based upon scores on a screening scale
72.4
Connell et al, (1982)
Queensland, 1978-1980
Australia:
Primary schools; stratified as rural, urban , or metropolitan
Verhulst et a1. (1985)
Zuid-Holland, the Netherlands: 1983
Vikan (1985)
North Troendelag County, Norway: 1979
Birth registries stratified by age .and sex; restricted to Dutch nationals All children born in North Troendelag County in 1969
Anderson et a1. (1987)
Dunedin, New Zealand : 1983-1984
Cohen et a1. (1987)
Albany and Saratoga counties, New York, USA: 1983-1984 Columbia, Missouri, USA: 1985 Ontario, Canada: 1983
Kashani et a1. (1987) Offord et a1. (1987) Bird et a1. (1988) Q
Puerto Rico, USA: 19851986
Percent Response Rate"
Sampling Unit
All surviving children born to mothers residing in Dunedin between 1971 and 1972 Multistage probability sample of households All public schools in Columbia Multistage probability sample of households Multistage probability sample of households
90.0 (75.8)
76.5
85.6
91.1 92.2 (87 .7)
Numbers in parentheses are second stage response rates (where available) .
Four of the eight surveys (Connell et a1., 1982; Vikan, 1985; Verhulst et al., 1985; Bird et al., 1988) used the multimethod-multistage approach of Rutter et a1. (1970) to ascertain potential cases. In this approach, rating scales completed by parents and/or teachers were used as firststage screening instruments. Subjects with scores above the cutoff score were identified as possibly disturbed and further evaluated. In all but one study using this technique (Connell et a1., 1982), a small sample of individuals with scores below the cutoff threshold were also selected for interview to assess the frequency of false negatives, i.e., those who were in fact disturbed but whose rating scale scores were below the cutoff score. In the second stage, children with scores above the cutoff score and the sample of those with scores below this value were interviewed using semistructured or structured psychiatric interview instruments. At this stage categorical diagnoses were made . The overall prevalence of disorder was determined at the conclusion of this two-stage ascertainment process. The other four investigations (Anderson et a1., 1987; Offord et al., 1987; Kashani et al., 1987; Cohen et al., 1987b) did not base case ascertainment upon the multimethod-rnultistage approach. All children and adolescents identified through the initial sampling procedure were eligible for diagnostic assessment. For those investigations using the multimethod-multistage approach, completion rates based upon first-stage parent questionnaires ranged from 76.5% to 92.2%. Response rates at the second-stage interview were reported as 75.8% (Verhulst et aI., 1985) and 87.7% (Bird et aI., 1988). Completion rates ranging from 72.4% to 91. 1% were noted in the other J.Am.Acad. Child Adolesc,Psychiatry, 29:1, Jan. 1990
four investigations. Response rates in these eight child studies are generally equivalent to those reported for the ECA samples of adult respondents (Regier et aI., 1984). Sociodemographic variables generally were unassociated with nonresponse (Vikan, 1985; Cohen et aI., 1987; Kashani et aI., 1987; Offord et al., 1987; Bird et aI., 1988). Accessibility to interview site (Bird et aI., 1988) and emigrant status (Vikan, 1985; Anderson et aI., 1987) were associated with nonresponse in three studies. Vikan (1985) reported no association between reports by professionals of mental health problems and participation. Verhulst et al. (1985) found first-stage screening scores unrelated to subsequent participation; in contrast, Bird et al. (1988) noted subjects scoring within the normal range were less likely to participate in the second-stage screening process. These findings suggest sample estimates of population prevalence are unlikely to be systematically underestimated due to response bias. Sample Size and Demographic Characteristics of Subjects Variations in sample size and age distribution are seen in the eight prevalence surveys (Table 2). One survey (Kashani et al., 1987) was based on a sample of 150 adolescents. In four others (Connell et al., 1982; Anderson et al., 1987; Cohen et al., 1987b; Bird et al., 1988), the number of subjects eligible for assessment ranged from 775 to 792, and three large surveys (Verhulst et al., 1985; Vikan, 1985; Offord et al., 1987) included at least 1,500 individuals . One of these (Verhulst et al., 1985) limited eligibility for diagnostic evaluation to a small subsample of participants (N = 334). In five of the eight surveys the number of subjects actually interviewed was less than 200; in one of these
77
BRANDENBURG ET AL. TABLE
Study Connell et al. (1982) Verhulst et al. (1985)
Vikan (1985) Anderson et al. (1987)
Cohen et al. (1987)
2. Prevalence of Psychiatric Disorders in Children and Adolescents in Eight Community Studies Sample Size
Age Range
779 (176)" 334 (116)
10-11
1,510 (139) 792 (792)
8, II
10
11
775 (775)
9-19
Kashani et al. (1987)
150
14-16
Offord et aI. (1987)
2,679 (194) 777 (386)
4-16
Bird et al. (1988)
Q
b
4-16
Prevalence 14.1
26.0 7.0 5.0 17.6 7.3
16.7 18.7 18.1 17.9 15.8 7.0
Numbers in parentheses indicate children who were interviewed. CGAS, Children's Global Assessment Scale.
studies (Offord et al., 1987) interviewed subjects were part of a pilot study. Three of the studies (Connell et al., 1982; Vikan, 1985; Anderson et al. , 1987) sampled children in the narrow age range of 10 to 11, while only a subsample of 8- and 11year-olds underwent structured interviews in a fourth (Verhulst et al., 1985). A broader age group of 4 to 16 was sampled in two other studies (Offord et al., 1987; Bird et al., 1988). Older children and adolescents were the focus of investigation in the Kashani et al. (1987) (ages 14 to 16) and Cohen et al. (1987) (ages 9 to 19) investigations. Study populations were composed of roughly equal proportions of males and females across all studies. Nearly all individuals in these investigations were nonHispanic Caucasians, with the exception of the survey conducted in Puerto Rico. Small numbers of persons of other racial and ethnic groups were included in some investigations . Instrumentation While single-informant investigations characterized nearly all prior epidemiological efforts, newer studies have broadened data collection to include information gathered from parents, teachers, and the subjects themselves. Table 3 presents the instruments used in these studies. Three types of rating scales were employed in these community-based studies of children: the Rutter Scales, (Rutter et al. , 1970), the Child Behavior Checklist (Achenbach and Edelbrock, 1983), and problem checklists designed to detect the presence of conduct disorder, hyperactivity (attentiondeficit disorder with hyperactivity), emotional disorder, and somatization (Boyle et al. , 1987). The Rutter Child Scale A and Rutter Child Scale B cover
78
Case Definit ion Rutter classification Rutter severity criterion DSM·Il/ criteria Severity rating scale: Moderate and Severe Severe only Rutter classification Rutter severity criterion and need for treatment DSM-Il/ Criteria Criteria met by one source Criteria met by more than one source DSM -Il/·R Criteria Severity scale composed of DISC symptom scales at least 2 SD above the mean DSM·Il/ Criteria Severity rating scale: moderate and severe DSM-Il/ Criteria Rutter severity criterion DSM·Il/ Criteria and CGAS
AND
STARR E. SILVER, PH.D.
Abstract. While sharing a new emphasis upon identifying discrete psychiatric disorders in children and adolescents, epidemiological field studies conducted during the past decade have used diverse ,methods o f case ascertainment and definition. Half used the multimethod-multistage approach to ascertain cases. Severity rating scales and measures of pervasiveness, parent-child concordance, and global functional impairment were employed to enhance the specificity of case definition. The majority of overall prevalence estimates of moderate to severe disorder range from 14 to 20%. Those investigations that use multiple methods to define caseness show greatest promise in identifying true cases in community samples. J. Am ; Acad. Child Adolesc. Psychiatry , 1990,29, 1:7683. Key Words: prevalence, identification of childhood disorder, caseness, multimethod-multistage approach.
The principal aims of descriptive epidemiological studies in child psychiatry are threefold: to estimate the overall prevalence of psychiatric disorder and of the specific disorders that together constitute overall prevalence, to identify correlates of those disorders, and to estimate the absolute number of affected individuals for planning mental health services. The purpose of this review is to present and discuss prevalence estimates of childhood disturbance from community surveys conducted in the past decade--a decade characterized by the development of a formal 'taxonomic system with explicit criteria to operationalize the diagnostic process and the creation of structured interview instruments designed to detect psychiatric disorders in community samples. These studies, through various methods, reflect efforts to enhance specificity in the definition of " caseness."
of clinical maladjustment among U.S. children at 11.8%. Teachers identified children as disturbed in 21 studies conducted before 1970; in four studies conducted during the 1970s, parents served as informants . In addition to using a single informant, these studies were characterized by use of a single method to identify disturbed children and youth . The emergence of a new generation of field studies in child psychiatry reflects two major developments : refinements in case ascertainment and definition that parallel the careful emphasis on design, field methods, and instrumentation exemplified by the NIMH Epidemiology Catchment Area (ECA) program (Eaton .et al. , 1984; Regier et aI., 1984) and, in some studies, application of the multimethodmultistage approach pioneered by British psychiatrist Michael Rutter and colleagues (Rutter et aI. , 1970) in new samples of children and adolescents . Sampling methods, the type of measures employed, and case definition profoundly impact prevalence estimates . These topics will be explored in detail before prevalence estimates from these studies are discussed.
Historical Perspective Past studies of the prevalence of childhood disorders did not describe the frequency of discrete psychiatric conditions in children, but instead reported the occurrence of global conditions such as "maladjustment" or "maladaptation" (Gould et aI., 1980). Based on a review of 25 prevalence studies conducted in the United States between 1928 and 1975, Gould et al. (1980) estimated the median prevalence
Populations and Samples Sampling Methodology and Nonresponse Over the past decade, published reports have described eight prevalence surveys of childhood and adolescent psychiatric disorder conducted in five Western developed nations (Table 1). Surveys have been conducted in Australia (Connell et aI., 1982), Norway (Vikan , 1985), the Netherlands (Verhulst et al., 1985), New Zealand (Anderson et al., 1987), and Canada (Offord et al. , 1987). Populations sampled in the United States include those in Missouri (Kashaniet al., 1987), Upstate New York (Cohen etal. , 1987), and Puerto Rico (Bird et aI. , 1988). Sampling units have included the year of birth, the school , and the household. While these studies have varied in the sophistication of the sampling method employed , most investigators have attempted to achieve representativeness in socioeconomic and/or population density indices. In those studies where schools were the sampling unit, institutionalized children were excluded from the sample (Connell et al., 1982; Kashani et aI., 1987); such children were excluded in the Canadian study as well (Offord et aI., 1987).
Accepted February 13, 1989. Dr. Friedman is Chairp erson and Profess or of Psychology , Departm ent ofEpidemiology and Poli cy Analysis, Florida Mental Health Institute, University of South Florida . Dr . Friedman is also Executive Director, and Dr. Silver is Research Director, Research and Training Center for Children' s Mental Health. Dr. Brandenburg is Assistant Professor ofEpidemiology and Biostatistics, College ofPublic Health , and Research Epidemiologist. This research is supported in part by the Nati onal Institute on Disability and Rehabilitative Research and the National Institute ofMental Health , Grant No . 008435138, and by the Florida Mental Health Institute . The authors thank Victoria Innis and Kris Keller fo r their assistance in manuscript preparation. Reprint requests to Dr. Friedman , Depa rtment ofEpidemiology and Policy Analysis, Florida Mental Health Institute, 13301 Bruce B . Downs Boule vard, Tampa , FL 33612-3899 . 0890·8567/90/290 I-D076$2.00/0© 1990by the American Academy of Child and Adolescent Psychiatry .
76
PREVALENCE OF CHILDHOOD PSYCHIATRIC DISORDERS TABLE
Study
1. Populations Sampled, Methods of Sampling, and Response Rates in Recent Epidemiological Investigations Population Sampled : Survey Dates
Method of Sampling Two-stage sampling of subjects based upon scores on a screening scale Two-stage sampling of subjects based upon scores on a screening scale Two-stage sampling of subjects based upon scores on a screening scale All available members of the birth cohort
79.0
All age-appropriate subjects available for follow-up
75.0
Random sample stratified by age and sex All age-appropriate children within eligible households Two-stage sampling of subjects based upon scores on a screening scale
72.4
Connell et al, (1982)
Queensland, 1978-1980
Australia:
Primary schools; stratified as rural, urban , or metropolitan
Verhulst et a1. (1985)
Zuid-Holland, the Netherlands: 1983
Vikan (1985)
North Troendelag County, Norway: 1979
Birth registries stratified by age .and sex; restricted to Dutch nationals All children born in North Troendelag County in 1969
Anderson et a1. (1987)
Dunedin, New Zealand : 1983-1984
Cohen et a1. (1987)
Albany and Saratoga counties, New York, USA: 1983-1984 Columbia, Missouri, USA: 1985 Ontario, Canada: 1983
Kashani et a1. (1987) Offord et a1. (1987) Bird et a1. (1988) Q
Puerto Rico, USA: 19851986
Percent Response Rate"
Sampling Unit
All surviving children born to mothers residing in Dunedin between 1971 and 1972 Multistage probability sample of households All public schools in Columbia Multistage probability sample of households Multistage probability sample of households
90.0 (75.8)
76.5
85.6
91.1 92.2 (87 .7)
Numbers in parentheses are second stage response rates (where available) .
Four of the eight surveys (Connell et a1., 1982; Vikan, 1985; Verhulst et al., 1985; Bird et al., 1988) used the multimethod-multistage approach of Rutter et a1. (1970) to ascertain potential cases. In this approach, rating scales completed by parents and/or teachers were used as firststage screening instruments. Subjects with scores above the cutoff score were identified as possibly disturbed and further evaluated. In all but one study using this technique (Connell et a1., 1982), a small sample of individuals with scores below the cutoff threshold were also selected for interview to assess the frequency of false negatives, i.e., those who were in fact disturbed but whose rating scale scores were below the cutoff score. In the second stage, children with scores above the cutoff score and the sample of those with scores below this value were interviewed using semistructured or structured psychiatric interview instruments. At this stage categorical diagnoses were made . The overall prevalence of disorder was determined at the conclusion of this two-stage ascertainment process. The other four investigations (Anderson et a1., 1987; Offord et al., 1987; Kashani et al., 1987; Cohen et al., 1987b) did not base case ascertainment upon the multimethod-rnultistage approach. All children and adolescents identified through the initial sampling procedure were eligible for diagnostic assessment. For those investigations using the multimethod-multistage approach, completion rates based upon first-stage parent questionnaires ranged from 76.5% to 92.2%. Response rates at the second-stage interview were reported as 75.8% (Verhulst et aI., 1985) and 87.7% (Bird et aI., 1988). Completion rates ranging from 72.4% to 91. 1% were noted in the other J.Am.Acad. Child Adolesc,Psychiatry, 29:1, Jan. 1990
four investigations. Response rates in these eight child studies are generally equivalent to those reported for the ECA samples of adult respondents (Regier et aI., 1984). Sociodemographic variables generally were unassociated with nonresponse (Vikan, 1985; Cohen et aI., 1987; Kashani et aI., 1987; Offord et al., 1987; Bird et aI., 1988). Accessibility to interview site (Bird et aI., 1988) and emigrant status (Vikan, 1985; Anderson et aI., 1987) were associated with nonresponse in three studies. Vikan (1985) reported no association between reports by professionals of mental health problems and participation. Verhulst et al. (1985) found first-stage screening scores unrelated to subsequent participation; in contrast, Bird et al. (1988) noted subjects scoring within the normal range were less likely to participate in the second-stage screening process. These findings suggest sample estimates of population prevalence are unlikely to be systematically underestimated due to response bias. Sample Size and Demographic Characteristics of Subjects Variations in sample size and age distribution are seen in the eight prevalence surveys (Table 2). One survey (Kashani et al., 1987) was based on a sample of 150 adolescents. In four others (Connell et al., 1982; Anderson et al., 1987; Cohen et al., 1987b; Bird et al., 1988), the number of subjects eligible for assessment ranged from 775 to 792, and three large surveys (Verhulst et al., 1985; Vikan, 1985; Offord et al., 1987) included at least 1,500 individuals . One of these (Verhulst et al., 1985) limited eligibility for diagnostic evaluation to a small subsample of participants (N = 334). In five of the eight surveys the number of subjects actually interviewed was less than 200; in one of these
77
BRANDENBURG ET AL. TABLE
Study Connell et al. (1982) Verhulst et al. (1985)
Vikan (1985) Anderson et al. (1987)
Cohen et al. (1987)
2. Prevalence of Psychiatric Disorders in Children and Adolescents in Eight Community Studies Sample Size
Age Range
779 (176)" 334 (116)
10-11
1,510 (139) 792 (792)
8, II
10
11
775 (775)
9-19
Kashani et al. (1987)
150
14-16
Offord et aI. (1987)
2,679 (194) 777 (386)
4-16
Bird et al. (1988)
Q
b
4-16
Prevalence 14.1
26.0 7.0 5.0 17.6 7.3
16.7 18.7 18.1 17.9 15.8 7.0
Numbers in parentheses indicate children who were interviewed. CGAS, Children's Global Assessment Scale.
studies (Offord et al., 1987) interviewed subjects were part of a pilot study. Three of the studies (Connell et al., 1982; Vikan, 1985; Anderson et al. , 1987) sampled children in the narrow age range of 10 to 11, while only a subsample of 8- and 11year-olds underwent structured interviews in a fourth (Verhulst et al., 1985). A broader age group of 4 to 16 was sampled in two other studies (Offord et al., 1987; Bird et al., 1988). Older children and adolescents were the focus of investigation in the Kashani et al. (1987) (ages 14 to 16) and Cohen et al. (1987) (ages 9 to 19) investigations. Study populations were composed of roughly equal proportions of males and females across all studies. Nearly all individuals in these investigations were nonHispanic Caucasians, with the exception of the survey conducted in Puerto Rico. Small numbers of persons of other racial and ethnic groups were included in some investigations . Instrumentation While single-informant investigations characterized nearly all prior epidemiological efforts, newer studies have broadened data collection to include information gathered from parents, teachers, and the subjects themselves. Table 3 presents the instruments used in these studies. Three types of rating scales were employed in these community-based studies of children: the Rutter Scales, (Rutter et al. , 1970), the Child Behavior Checklist (Achenbach and Edelbrock, 1983), and problem checklists designed to detect the presence of conduct disorder, hyperactivity (attentiondeficit disorder with hyperactivity), emotional disorder, and somatization (Boyle et al. , 1987). The Rutter Child Scale A and Rutter Child Scale B cover
78
Case Definit ion Rutter classification Rutter severity criterion DSM·Il/ criteria Severity rating scale: Moderate and Severe Severe only Rutter classification Rutter severity criterion and need for treatment DSM-Il/ Criteria Criteria met by one source Criteria met by more than one source DSM -Il/·R Criteria Severity scale composed of DISC symptom scales at least 2 SD above the mean DSM·Il/ Criteria Severity rating scale: moderate and severe DSM-Il/ Criteria Rutter severity criterion DSM·Il/ Criteria and CGAS
