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C
Defining and Classifying Disability in Children

Rune J. Simeonsson*

“during the third or fourth month, the most important acquisition being the power of balancing the head on the shoulders; the absence of this power at this stage was one of the earliest signs of mental deficiency”

(Forsyth, 1915, p. 535).

Defining and measuring disability in the first two decades of life has been a uniquely challenging task. From infancy to adolescence, it is a period marked by dynamic changes in body structures and functions; the acquisition of physical and mental skills; and progressive steps toward independence of movement, thought, and behavior. In contrast to the relatively stable characteristics of the adult, the evolving characteristics of the child represent a moving target, complicating the task of assessing function and distinguishing significant limitations from variations in normal developmental processes. The younger and less mature that the child is, the greater the challenge has been to define disability.

In the history of childhood disability (Schalick, 2000), earlier approaches to defining disability took the form of observing physical signs (Down, 1887) or noting discrepancies in the appearance of basic maturational skills (Forsyth, 1915). These approaches are still followed today as strategies for the identification of developmental problems of infants and young children, although contemporary determination of disability is now often linked to the documentation of diagnosed conditions, such as trisomy 21. As the child develops, observation and assessment are increasingly used as documentation strate-

*  

Rune J. Simeonsson, Ph.D., M.S.P.H., Professor of Education and Research Professor of Psychology, University of North Carolina at Chapel Hill and Adjunct Professor of Medical Psychology, Department of Psychiatry, Duke University. The analyses and views presented in this workshop paper are those of the author and not necessarily those of the Institute of Medicine Committee on Disability in America: A New Look.



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Workshop on Disability in america A new look: Summary and background papers C Defining and Classifying Disability in Children Rune J. Simeonsson* “during the third or fourth month, the most important acquisition being the power of balancing the head on the shoulders; the absence of this power at this stage was one of the earliest signs of mental deficiency” (Forsyth, 1915, p. 535). Defining and measuring disability in the first two decades of life has been a uniquely challenging task. From infancy to adolescence, it is a period marked by dynamic changes in body structures and functions; the acquisition of physical and mental skills; and progressive steps toward independence of movement, thought, and behavior. In contrast to the relatively stable characteristics of the adult, the evolving characteristics of the child represent a moving target, complicating the task of assessing function and distinguishing significant limitations from variations in normal developmental processes. The younger and less mature that the child is, the greater the challenge has been to define disability. In the history of childhood disability (Schalick, 2000), earlier approaches to defining disability took the form of observing physical signs (Down, 1887) or noting discrepancies in the appearance of basic maturational skills (Forsyth, 1915). These approaches are still followed today as strategies for the identification of developmental problems of infants and young children, although contemporary determination of disability is now often linked to the documentation of diagnosed conditions, such as trisomy 21. As the child develops, observation and assessment are increasingly used as documentation strate- *   Rune J. Simeonsson, Ph.D., M.S.P.H., Professor of Education and Research Professor of Psychology, University of North Carolina at Chapel Hill and Adjunct Professor of Medical Psychology, Department of Psychiatry, Duke University. The analyses and views presented in this workshop paper are those of the author and not necessarily those of the Institute of Medicine Committee on Disability in America: A New Look.

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Workshop on Disability in america A new look: Summary and background papers gies, but variability in the nature and rate of development continues to be a source of confounding in the identification of disability (Simeonsson and Rosenthal, 2001). The lack of theory and the lack of consistent concepts of disability in childhood have resulted in identification and classification approaches that have been idiosyncratic to disciplines or service systems and taken the form of diagnoses, syndromes, or categories. Although the definition and classification of disability in children are issues of current significance, they are not new problems. Concerns about diagnoses, categorical assignment, and the associated labeling of children with disabilities prompted a request for a coherent classification system in the early 1970s by then Secretary of Health, Education and Welfare Elliot Richardson (Hobbs, 1975a). In addition to the problem of labeling and its impact on children, the task of the project was also to address the inappropriate use of psychometric instruments and classification practices in the determination of disability in children from minority groups. The project resulted in two publications, with the first, Issues in the Classification of Children (Hobbs, 1975a), summarizing problems and challenges. In the second book, The Futures of Children, Hobbs (1975b) recommended a functional basis for the classification of children’s disabilities. The functional approach recommended by Hobbs was not realized, and the categorical basis for determining the eligibility of children for funding and services continues to raise concerns in the context of fragmented and incomplete services (Hughes et al., 1996; Newacheck et al., 1998). Although the terminology for the concerns defined in the 1970s may have changed, many of the problems raised at that time remain the same today, requiring revisiting of the identification and the classification issues three decades later. The purpose of this paper is to (1) review concepts of development and disability; (2) present models and representative data on childhood disability; (3) describe current issues; and (4) identify emerging issues to advance the definition, measurement, and classification of disability in childhood. CONCEPTS OF DEVELOPMENT AND DISABILITY Concepts of Atypical Development Although there is no universal standard for defining childhood disability, a number of concepts have framed disability related to atypical development. In reviewing the research on different outcomes for children who have experienced significant developmental risk factors, Sameroff and Chandler (1975) described main-effect, interactional, and transactional models to capture the evolving findings on the roles of biological and environmental factors in child development. In the main-effect model, a nurturist view

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Workshop on Disability in america A new look: Summary and background papers posited that a good environment could compensate for a poor biological state, whereas in the nativist view, the biological state (good or poor) determined the outcome. The main-effect model was seen as static, as it failed to account for interactive effects on development. The interactive model of developmental outcome posited intermediate outcomes. However, recognition of the ongoing reciprocal influences of environment on the child and the child on the environment led to the proposal of a transactional model to account for different outcomes of development. The transactional model has been drawn upon widely as a framework for designing and evaluating interventions for children with disabilities and their families. An important question pertaining to disability in childhood has focused on whether atypical development represents qualitative differences or quantitative lags in development. This question has been addressed in contributions by Zigler (1969) and Inhelder (1966, 1968). Although both contributions were framed with reference to children with mental retardation, the main premise seems applicable to children with any disability. Zigler (1969) proposed that the cognitive development of children with mental retardation that was not organic in origin was similar in structure and followed a similar sequence to that of children without disabilities. Within the framework of Piaget’s theory of cognitive development, Inhelder (1966, 1968) advanced a similar concept of an invariant sequence to describe the delayed rate of cognitive development in individuals with mental retardation. Mental retardation was characterized by a delayed progression through stages of development and an ultimate failure to achieve the ability to perform formal operations at maturity, representing a “false equilibrium,” that is, an incomplete level of cognitive development. The severity of mental retardation corresponded to fixation at lower stages of cognitive development. As noted above, although the rate of development of children with disabilities may differ from that of children without disabilities, the general assumption is that the sequence and structure of development in children with disabilities are similar to that of all children. Furthermore, children with disabilities, as all children, are assumed to be characterized by individual differences. Theory as well as extensive research has supported this premise and formed the basis for conceptualizations of variations in development. It may be useful to consider three developmental perspectives on disability: (1) the continuum of reproductive casualty, (2) the continuum of care-taking casualty, and (3) the continuum of central nervous system (CNS) dysfunction. The Continuum of Reproductive Casualty Almost 40 years ago, Pasamanick and Knobloch (1966) became intrigued with the variations in the developmental outcomes of children who

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Workshop on Disability in america A new look: Summary and background papers had experienced pre- and perinatal complications. On the basis of a systematic examination of the developmental consequences of pregnancy and delivery complications, they advanced the concept of a continuum of reproductive casualty to define the range of possible outcomes due to insult in the prenatal period. This range of outcomes was proposed to reflect the contributions of three factors: the nature, the extent, and the developmental timing of the insult. The result of complications at one end of the continuum was nonsurvival, whereas the complications at the other end of the continuum were negligible. For infants who survived the complications, “there must remain a fraction so injured who do not die, but depending on the degree and location of the trauma, go on to develop a series of disorders extending from cerebral palsy, epilepsy and mental deficiency, through all types of behavioral and learning disabilities, resulting from lesser degrees of damage sufficient to disorganized behavior development and lower thresholds to stress” (Pasamanick and Knobloch, 1966, p. 7). Central to the concept of the continuum of reproductive casualty was the assumption that the range of outcomes expressed in different manifestations of disability, such as mental retardation, cerebral palsy, and learning disability, reflected the differential effects of complications on common developmental processes (Baum, 1977; Ounsted, 1987). This concept has been used to interpret the long-term outcomes for low-birth-weight children (Forfar et al., 1994) and for findings that associate obstetric complications with conditions , such as mental retardation, autism, learning disabilities, and disorders resulting from organic conditions or toxic exposures (Eaton et al., 2001). By defining disability in terms of the various outcomes of prenatal complications, the continuum of reproductive casualty can be seen as a precursor of later conceptualizations in which disability is seen as universal with problems manifested on a continuum. The Continuum of Caretaking Casualty After the introduction of the concept of the continuum of reproductive casualty, there was a growing recognition that the outcomes for children experiencing pre- and perinatal complications were influenced by a complex of factors. Baum (1977) pointed out that the outcomes of infants experiencing significant perinatal insults were not consistent with the reproductive casualty continuum hypothesis and recommended that more attention needed to be paid to the role of the postnatal environment on developmental outcomes. Of particular interest was recognition of the impact of environmental factors on the developing child beyond the pre- and perinatal period with the potential to account for developmental outcomes (Roosa et al., 1982). On the one hand were studies demonstrating that the outcomes for children with prenatal or birth complications could be posi-

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Workshop on Disability in america A new look: Summary and background papers tively modified by environmental interventions. On the other hand were findings showing that the development of children with uneventful fetal histories could be seriously delayed or distorted by certain caregiving histories. The caregiving environment thus became a factor of significant interest as a variable affecting the developmental outcomes of children. This emphasis on the caregiver’s role in influencing outcome was central to the articulation of the concept of the continuum of caretaking casualty by Sameroff and Chandler (1975). The major premise of this concept is that developmental outcome is not defined by pre- or perinatal factors alone but is a product of continuing transactions between the child and the stimulation and nurture provided by the caregiver in the child’s development. Similar to the concept of the continuum of reproductive casualty, the concept of the continuum of caretaking casualty proposes that the developmental outcomes of children are expressed as a range of manifestations rather than as discrete entities. The utility of this concept can be illustrated in a study of the affective development of young children reared in different caregiving environments (Smyke et al., 2002). Consistent with the concept, children experiencing greater social deprivation manifested greater disturbances. The concept of caretaking casualty thus extends the continuum of reproductive casualty and defines differences in children with disabilities as developmental expressions of processes occurring in the prenatal period as well as the postnatal period. The Continuum of CNS Dysfunction A third concept advanced to define disability in childhood is the continuum of CNS dysfunction. Whereas the previous two concepts were linked in terms of their development, the continuum of CNS dysfunction was advanced without a link to the others. Capute and Palmer (1980) used the term to emphasize the associated deficits that stem from a common underlying dysfunction of the CNS. For optimal assessment and treatment of the developmentally disabled child, both the spectrum of expressed disability and the underlying dysfunction need to be recognized (Capute et al., 1981). In this model, specific conditions associated with disability are grouped under the three major conditions of cerebral palsy, mental retardation, and communicative disorders. Cerebral palsy is considered prototypic of developmental disabilities, as individuals with this condition often have cognitive as well as communicative deficits. Communicative deficits were defined to include both central dysfunctions (language disorder, learning disability, or autism) and peripheral dysfunctions (hearing or visual impairment). Distinguishing between the spectrum of disabilities and the underlying dysfunction is important for the detection and the diagnosis of disabilities in children. Two associated concepts are advanced in an elaboration of the con-

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Workshop on Disability in america A new look: Summary and background papers TABLE C-1 Complementary Contributions of Three Continuum Concepts to Defining Disability in Childhood Continuum Disability as Developmental Outcome Complementary Contribution Continuum of reproductive casualty Range of developmental outcomes as a function of nature and timing of pre- or perinatal insult Disability as a variable expression of prenatal and perinatal factors Continuum of caretaking casualty Range of developmental outcomes as a function of transactions between child and postnatal environment Disability as variable expression of postnatal experiences Continuum of CNS dysfunction Range of developmental outcomes as a function of the location, nature, and severity of the underlying CNS dysfunction Disability as variable expression of motor-sensory and central-peripheral dysfunction tinuum of CNS dysfunction: deviancy and dissociation. Both are proposed to facilitate the identification of problems and atypical development. Deviancy refers to deviations of a child’s abilities from normal values within a certain domain. The dissociation phenomenon refers to discrepancies in level of functioning from one domain to another, for example stronger motor skills but weaker language skills or stronger mental skills but weaker motor skills. Recognition of the deviancy phenomenon may thus contribute to the detection of a child whose behavior is atypical and whose subsequent development needs careful monitoring. Sensitivity to the dissociation phenomenon could contribute to the documentation of a child’s relative strengths and deficits. This is evident in children with motor impairments, for example, whose language abilities are often advanced relative to their motor abilities. In summary, the continuum of outcomes attributed to reproductive or caretaking complications, or CNS dysfunction have contributed to conceptualizations of disabilities based on a model of child-environment interactions. Specifically, the three continuum concepts make this contribution by emphasizing the variability of common developmental processes (Table C-1). Their contributions advance the developmental basis for conceptualizing the dimensions of childhood disability. These concepts provide an alternative to the medical model, which fo-

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Workshop on Disability in america A new look: Summary and background papers cuses on symptoms of health conditions within the child. The premise of a continuum of outcomes supports a functional model that encompasses commonalities and variations in development across major domains. These developmental domains reflect the manner in which the child actively explores and acts upon the physical and the social environments. The domains include cognition, communication, social development, and behavior. MODELS OF DISABILITY IN CHILDREN Medical Model Although they may not be consistently defined, medical, social, and functional models have generally framed definitional, measurement, and classification issues related to disability in adults. In the absence of a specific model for defining disability in childhood, these have also been applied in considering disability of children and youth. Reference to the medical model implies that the locus of the disability is in the person (Marks, 1997) and that disability is defined by the manifestation of a health condition in the form of anomalies or impairment of physical or mental structures or function. Documentation of disability usually takes the form of recording the diagnoses, syndromes, or signs or symptoms that meet the criteria for assignment to a category. In health, mental health and health related settings, codes from the International Classification of Diseases, 9th Revision (ICD-9) and the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) are likely to be the basis for determining a child’s eligibility for services and support. In education, assignment to 1 of 13 categories under Part C of the Individuals with Disabilities Education Improvement Act (IDEA; P.L. 94-142) defines eligibility for special education services. These categories were put in place in 1976 with the establishment of special education under P.L. 94-142 and reflect a medical model because the categories either are diagnosed conditions (e.g., mental retardation, autism, traumatic brain injury [TBI], and learning disabilities) or specify criteria based on physical or mental impairments (e.g., auditory and visual impairments and severe emotional disturbance). It should be noted, however, that the categorical terms are specific to the field of education and do not necessarily correspond to the diagnoses defined by ICD-9 or DSM-IV-TR classifications. The categories reflect a medical model perspective and were designated as “handicaps” in the original legislation and then as “disabilities” in the 1991 reauthorization of IDEA. The autism category was added in 1991, and the category for TBI was added in 1997. Interestingly, attention deficit-hyperactivity disorder (ADHD), a highly prevalent childhood condition, does not constitute a formal IDEA category.

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Workshop on Disability in america A new look: Summary and background papers To be served under IDEA, children with ADHD must qualify under the category of other health impairment. The idiosyncratic nature of the 13 categories is further illustrated by the fact that children who are deaf and blind are assigned to the deaf-blind category, whereas children with other co-occuring conditions are assigned to the category of “multiple disabilities.” The fact that states can exercise discretion in measurement approaches to determine eligibility for assignment to a category lowers the specificity of information about the characteristics of the children in that category and raises questions about the aggregation of data by categories. However, as the federal government requires the states to report annually on the numbers of students served in special education under these categories, the resulting data do provide estimates of the prevalence of childhood disability. An analysis of ten-year data (www.IDEAdata.org) indicates that population prevalence rates for all children served in special education ages 3 to 21 increased from 7.44 to 8.56 percent from 1993 to 2003. Limiting the analysis to the 6- to 21-year-old group or 6- to 11-year-old group revealed increasing rates over the decade from 8.21 to 9.05 percent and 10.86 to 11.23 percent, respectively. An analysis of the prevalence rates by disability categories for students 6 to 21 years of age reveals that the five most prevalent categories in 2003 were learning disabilities (4.28 percent), speech and language impairments (1.70 percent), mental retardation (0.87 percent), emotional disturbance (0.73 percent), and other health impairment (0.73 percent). The prevalence rate for each of the remaining categories was 0.2 percent or less. Although the rates for most categories have remained relatively stable from 1993 to 2003, there is a gradual decline in the rate for mental retardation and relatively marked increases in the rates for other health impaired (0.14 to 0.68 percent), autism (0.03 to 0.21 percent) and for developmental delay from 1997 to 2003 (0.01 to 0.10 percent). Social Model The emergence of the disability movement has been characterized by definitions of disability from the perspective of individuals with disabilities (Kaplan, 2000). A major reaction to the medical model resulted in the articulation of a social perspective on disability, the social model in Britain, and the minority group model in the United States. The basic assumption of these models was a rejection of seeing disability as a characteristic within the person and seeing it instead as a social construction defined by discrimination and exclusion by mainstream social environment (Marks, 1997). The emphasis on environmental barriers and the denial of human rights in the social model of disability has served as a powerful premise for political action and advocacy. Although the social model has contributed signifi-

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Workshop on Disability in america A new look: Summary and background papers cantly to the formulation of inclusive policies and practices for environmental access for adults, its influence on policies and practices involving children is less obvious. Munn (1997) has maintained that a weakness of the social model is that it failed to adequately account for children with disabilities, who are a minority within the minority of individuals with disabilities. Their minority status is defined by the fact that “disabled children are twice ignored and they are also twice vulnerable to the lack of resource, the stigma and stress of disability, together with the strain on their already compromised development and family relations” Munn (1997, p. 484). Munn thus argues for a movement away from categorization based on physical criteria and the incorporation of a developmental emphasis in the minority group model. The concepts of least-restrictive environments and full inclusion in placements for special education students are consistent with the social-minority group model. In a somewhat different context, Landsman (2005) draws on the social model in interpreting the nurturing experience of mothers of children newly diagnosed with disabilities. Over time, mothers replaced their problem-oriented focus based on the medical model with a social model focused on integration and acceptance of their children. Functional Model Although “functional model” may not be a term that has been formalized or used with the same level of consensus as the medical and social models, it seems appropriate to use the term in reference to a number of contributions to research and practice that have defined disability as the basis of functional limitations. A variety of contributions began to emerge in the last decade, advocating alternative ways of conceptualizing and measuring disability in childhood. In a line of research, Stein and colleagues (Stein et al., 1993; Westbrook et al., 1998; Stein and Silver, 1999; Stein and Silver, 2002) examined the utility of a noncategorical approach to the identification of children with chronic conditions and disabilities. Based on the language of the Americans with Disabilities Act (P.L. 101-336), three criteria for the definition of disabling or chronic conditions in childhood were specified. A disability was defined on the basis of the fact that it (1) was a consequence of an ongoing health condition, (2) was manifested in functional limitations or dependence on compensatory mechanisms or the use of services or care beyond usual or normal levels for the age group, and (3) lasted or was expected to last 12 months or more. By use of a random sample of households in a national data set, a comparative analysis identified 9 percent as having a disability on the basis of functional limitations, 10 percent as having a disability on the basis of dependence on compensa-

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Workshop on Disability in america A new look: Summary and background papers tory devices, and 13 percent as having a disability on the basis of the use of services or care beyond the norm for the child’s age. Overall, 18 percent of children under the age of 18 years were identified as having a disability (Westbrook et al., 1998). In another study with data from the 1994 National Health Interview Survey (NHIS), 9.6, 5.1, and 10.6 percent of children were identified respectively on the basis of having functional limitations, relying on compensatory resources, and using services or care beyond levels usual or normal for their age group (Stein and Silver, 1999). The overall proportion of the sample identified to have at least one of these characteristics was 14.8 percent. Also using the 1994 NIHS data set, Hogan et al. (1997) generated prevalence estimates of disability in childhood based on indicators of functional limitations in mobility, self-care, communication, and learning ability. Analyses based on data for school-aged children between 5 and 17 years of age identified 10.6 percent with limitations in learning, 5.5 percent with communication limitations, 1.3 percent with limitations in mobility, and 0.9 percent with limitations in self-care. Socioeconomic differences were associated with higher rates of disabilities in children. Other demographic factors associated with higher rates of disability were found to include male gender and being a child of school age (Mudrick, 2002). In a comprehensive analysis of the 1994-1995 NHIS Disability Supplement (NHIS-D), Fedeyko and Lollar (2003) assigned 42 of the NHIS-D questions to one of eight Activity and Participation domains used in the World Health Organization’s International Classification of Functioning, Disability and Health (ICF) (WHO, 2001). The results revealed that 12.1 percent of 5- to 17-year-olds reported a limitation compared to 17.2 percent for those 18 to 64 years of age. In an analysis of limitations for 5- to 17-year-olds by domains, 1.3 percent reported sensory limitations, less than 1 percent reported movement and mobility limitations, 4.8 percent reported communication limitations, however, 9.4 percent reported learning limitations. The concept of functional limitations has also been applied in epidemiological studies to document the prevalence of mental health problems in children and youth. As has been true for other disabilities, definitions of mental illness and emotional disturbance vary in terms of the criteria for the nature and the severity of the conditions. Such variability of definitions in the two primary settings of mental health and education complicates both the identification of children needing help and the coordination of services for them. In recognition of the impact of such definitional variability on the estimation of prevalence, Narrow et al. (1998) used an epidemiological survey to compare three federal definitions of severe mental illness (one

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Workshop on Disability in america A new look: Summary and background papers education definition and two mental health definitions) in children and youth between 9 and 17 years of age. The term serious emotional disturbance (SED) was used in the education definition based on IDEA and in a mental health definition advanced by the Alcohol, Drug Abuse and Mental Health Administration Reorganization Act of 1992 (P.L. 102-321). These two definitions differed from the other mental health definition in that they required documentation of functional limitations, in addition to a formal diagnosis of the disorder. The results revealed a range in the proportion of children whose conditions met the criteria of severe mental illness or SED, with 3.0 percent meeting the criteria for diagnosed disorders, 11.8 percent meeting the criteria for the IDEA-based definition, and from 12.1 to 22.6 percent meeting the criteria for the mental health-based SED definition. The prevalence of SED was also examined in two studies involving the Great Smoky Mountains Study of Youth, which monitored 9-, 11-, and 13-year-old children over a period of 8 years. In the first study, the proportion of children with an SED identified on the basis of any diagnosed mental health disorder was 20.3 percent, whereas the proportion identified on the basis of an SED definition was 4 to 8 percent (Costello et al., 1996). A subsequent follow-up study found a prevalence of 13.3 percent of any diagnosed disorder, whereas the prevalence of SED was 6.8 percent (Costello et al., 2005). These findings and those of Narrow et al. (1998) yield population prevalence rates of SED in children that are significantly higher (4 to 11.8 percent) than the rates in special education under IDEA (0.73 percent). Prevalence rates much closer to those reported by IDEA were found by Halfon and Newacheck (1999) in an analysis of the 1992 and 1994 NHIS data sets. For children under 18 years of age, the prevalence of disability associated with a mental health condition was 2.13 percent. Of those children, 0.1 percent were characterized by severe disability, 1.92 percent were characterized by moderate disability, and 0.1 percent were characterized by mild disability. The findings from the studies described above demonstrate that definitions play an important role in estimating the prevalence of disability associated with mental health conditions in children. They also illustrate the importance of distinguishing between the documentation of underlying health conditions and the documentation of disability defined by the manifestation of functional limitations. CURRENT ISSUES As noted earlier in this paper, there is no common, agreed-upon model of childhood disability. Instead, a variety of models, concepts, and definitions have been employed to describe the sources, nature, and consequences

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Workshop on Disability in america A new look: Summary and background papers of atypical development in terms of disability and chronic conditions. Available prevalence estimates vary as a function of the definitions chosen by different researchers and research sponsors. A significant consequence of this variability is an inadequate epidemiology of disability in childhood. Other factors also contribute to the current lack of an adequate epidemiology of disability in childhood, for example, variability in the selection of age groups for study and inconsistent criteria for the labeling and classification of disabilities. As illustrated in the studies described above (Stein and Silver, 1999; Westbrook et al., 1998), the overall prevalence of disability and chronic conditions among children under 18 years of age have been estimated as high as 18 percent. Both studies used national data sets, with the findings reported by Stein and Silver (1999) based on data from the 1994 NHIS. In other studies that have used the 1992 or 1994 NHIS data set with different definitions of disability, the prevalence of disability among 5- to 17-year-olds was estimated to be 7.5 percent (LaPlante and Carlson, 1995), 6.5 percent (Newacheck and Halfon, 1998) and 12.1 percent (Fedeyko and Lollar, 2003) and for children under 18 years of age, 13 to 17 percent (Stein and Silver, 2002). These population prevalence figures are from 30 percent to almost 100 percent higher than the prevalence (9.05 percent) of school age children, 6 to 21 years of age, who are served in special education based on categorical assignment. The variability of the estimates can be attributed to at least two sources: how disability was defined and the grouping of children by age for analyses. The noncategorical definition of Stein and colleagues focused on the identification of children for whom the consequences of a health condition manifested as dependence on compensatory mechanisms, functional limitations in activities, or an extensive need for services or care. The estimates provided by LaPlante and Carlson (1995) and Newacheck and Halfon (1998) were based on the severity of limitation in the major activities of engaging in play (children under 5 years of age) or attending school (children from 5 to 17 years of age) whereas the results provided by Fedeyko and Lollar (2003) did not take degree of limitation into account. The second source of variability contributing to an inadequate epidemiology of childhood disability is inconsistency in the identification of age groups for analysis. In the studies, described above, that used the NHIS data sets, for example, data are reported for 13 different age groups. LaPlante and Carlson (1995) report their findings by age group for children under 5, 5 to 13, and 14 to 17 years of age and overall for those 5 through 17 years of age. In Newacheck and Halfon’s (1998) study, the age groups are under 6, 6 to 11, and 12 to 17 years and overall for children under 18 years of age. Stein and Silver (1999) report their findings for the age groups of under 3, 4 to 6, 7 to 11, and 12 years old and older and overall for

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Workshop on Disability in america A new look: Summary and background papers children under 18 years of age. The combination of definitional differences and the overlap of age groups across studies complicate the interpretation and use of epidemiological studies of disability in children at a national level. Another issue contributing to problems in estimating disability in children and youth is the lack of a common standard for naming and classifying disabilities and chronic conditions. The approaches used to name and classify disabilities in children vary as a function of the disciplines or the agencies providing services to children. Thus, even though the nature of the child’s disability or chronic condition is the same across different settings, disciplines and agencies use different criteria and systems to define and classify the child’s condition. In health and mental health settings, children are assigned diagnoses on the basis of the definitions in ICD-9 and DSM-IV-TR (First and Pincus, 2002). Increasingly, syndromes are also being used to define children with disabilities in clinical as well as research contexts. In educational settings, children with disabilities are assigned to 1 of 13 IDEA categories that are based on underlying impairments. For children who are under 18 years of age and who are in contact with the Social Security System, eligibility for supplemental support is based on satisfying three elements of the definition of disability: (1) a medically determinable physical or mental impairment (2) that results in marked and severe functional limitations and (3) that has lasted or that is expected to last a year or to result in death. Determination of whether the child’s condition satisfies the definition of disability is based on the correspondence of the child’s manifested problems with the conditions in the List of Impairments (SSA, 2005). The List of Impairments constitutes a classification of functional limitations as well as diagnosed diseases and disorders across 15 sections, ranging from growth impairments to the immune system (SSA, 2005). A review of the definitional approaches associated with these programs in health, education, and social services reveals that although all approaches are based on a medical model, there is no direct correspondence between the definitional approaches and the definitions or the associated systems for the classification of disabilities. As many of the children with disabilities and chronic conditions will be in contact with all three of these settings, the lack of a common standard and language of disability complicates the derivation of data regarding needs and services. It also limits interdisciplinary and inter-agency communication and planning of integrated services. Inconsistency in the naming of identified populations is a fourth issue characterizing current policy and practice related to children with disabilities. At the broadest level this issue is reflected in the overlap of populations described by the terms “disability” and “chronic conditions” in prevalence studies. The premise that disability is chronic and often associated with an observed or inferred underlying health condition is accepted. At issue is the

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Workshop on Disability in america A new look: Summary and background papers fact that the terms chronic conditions and disability do differ (Aron et al., 1996) and should be differentiated with reference to inclusion and exclusion criteria. The categories under IDEA illustrate the lack of consistent criteria for defining disability. Under IDEA, disabilities are defined as conditions such as mental retardation, hearing or vision impairment, learning disabilities, autism, and traumatic brain injury; children having these conditions are eligible for special education. With the exception of the category of developmental delay (available for use with children up to the age of 9 years), the remaining categories require evidence that the child has “a condition.” The criteria for documenting that a child has a condition, however, are not based on a common dimension but vary from condition to condition. Thus, the criteria for mental retardation are based on measured intelligence, for traumatic brain injury the focus is on etiology, and for autism the focus is on symptoms consistent with a diagnosis. The criteria used to document learning disabilities in special education have changed over time, with the criteria in the 2004 reauthorization of IDEA reflecting a shift from the documentation of a significant discrepancy between intelligence and achievement to evidence of significant limitations in language use. A final illustration of inconsistencies in IDEA categories is that of “other health impairment.” Although chronic disease conditions meet the criteria for this category, it is not clear on what basis children with problems of attention and activity (ADHD) are eligible for special education under this category. The issue of variable criteria for defining disability is also illustrated in the List of Impairments (Part B) for disability evaluation under Social Security. As noted earlier in this paper, the List of Impairments consists of 15 sections that encompass body systems, physical and mental disorders, as well as a loss or limitations of function. The criteria for defining disability differ depending on whether the identified condition is a disorder, a disease, or limitations of function. EMERGING ISSUES As stated at the beginning of this paper, concerns about the definition, measurement, and classification of disability in childhood are not new. The broad issues raised in the project on the classification of children in 1975 are consistent with those now being faced three decades later. These issues focused on the need for a comprehensive approach that includes the spectrum of disabling conditions, that recognizes the influence of environmental factors on development and disablement (Verbrugge and Jette, 1994), and that places emphasis on functioning rather than diagnoses as the basis for defining disability (Lollar and Simeonsson, 2005). The review of concepts

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Workshop on Disability in america A new look: Summary and background papers and models in this paper has illustrated a number of contributions that support the use of such a comprehensive approach. The transactional model has reinforced the significance of the child-environment interaction in defining developmental outcomes. The concepts positing a continuum of outcomes attributed to reproductive casualty, caretaking casualty, and CNS dysfunction are consistent with childhood disability expressed as dimensional rather than discrete entities. Furthermore, although the medical model is still pervasive in defining disability through the use of health classifications (ICD-9 and DSM-IV) and disability categories (IDEA), there is a growing reliance on the estimation of the prevalence of functional limitations in national surveys. Although there is variability in the prevalence data derived from such surveys, they illustrate the use of functional data in estimating the prevalence of disability in childhood. A central issue is the need for a comprehensive approach that is inclusive of the manifestations of disability in children. The differentiation of underlying health conditions from limitations in the performance of activities has increasingly been recognized as the basis for defining disability. With the publication of the ICF, a framework and classification is available for documenting disability (see discussion in Appendix B). ICF draws on a biopsychosocial framework in its portrayal of human function across the dimensions of Body Structures and Function, Activities, and Participation in life roles. Environmental Factors are recognized as having an ongoing role in mediating a person’s performance of activities and participation in major life areas. ICF formalizes the functional model of disability by defining the dimensions of universal, human characteristics, providing a standard taxonomy for the documentation of disability in terms of impairments of function, activity limitations, and participation restrictions. The content of the main volume of ICF, however, was not sufficiently sensitive to the developmental aspects of functioning in children, particularly young children (Simeonsson et al., 2003). A derived version of ICF for children and youth (ICF-CY) has been under development, with publication expected by WHO in 2006. A primary focus in the development of the ICF-CY has been content that captures the activities of the developing child in the home, school, and community environments (Simeonsson et al., 2003). This has been done by extending the coverage of the main ICF volume through the expansion of content and the provision of increased detail. The person-environment focus of the transactional model of developmental outcome (Sameroff and Chandler, 1975) is consistent with the biopsychosocial perspective of ICF-CY, which emphasizes the ongoing influence of the environment on the child’s functioning. New codes in the ICF-CY have been added for Body Functions and Structures, Activities, Participation, and Environmental Factors to capture the growth and devel-

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Workshop on Disability in america A new look: Summary and background papers opment of infants, toddlers, children, and adolescents. These new codes represent significant areas of development and include sensory exploration, self-regulation, symbolic and social play, communication, learning, and meeting task demands. The dimensional framework of ICF-CY offers a structure that can be used to define disability in terms of functional limitations in children’s performance of activities and participation in major life roles appropriate for their age. Three applications of ICF-CY are proposed below to address the issues on variability in defining childhood disability raised in this paper. A first recommendation is that functional limitations be defined by the IFC-CY domain of Activities and Participation. This would involve the identification of a limited number of codes in a set that represent key indicators of child functioning, such as communication, mobility, and learning. One or more codes from a given set could be used in surveys or in screening or assessment instruments to ensure consistent measurement of the particular indicator or area of functioning. This approach has been used in medicine to generate core sets; however, the focus in these applications has been to identify a limited set of codes associated with a specific disease entity (Grill et al., 2005). In this proposed application for the documentation of disability in childhood, the focus is on core sets associated with developmental indicators. A second recommendation is to establish standard age groups for use in the analysis and reporting of data to improve the comparability of prevalence estimates across different assessments. The age groups currently used to report special education data (0 to 2, 3 to 5, 6 to 11, and 12 to 17 years of age) are recommended for adoption as standards for all studies, as they are (1) consistent with the stage divisions of developmental theories, (2) compatible with the age groupings of existing programs and services for children, and (3) already well established in education. Table C-2 illustrates identification of potential ICF-CY codes by age groups for key indicators, similar to those reported in the studies reviewed in this paper. In practice, identification of best codes would require the selection on the basis of research findings. A third recommendation is that children’s health conditions be documented by codes from the domains of Body Functions and Body Structures. This would avoid the heterogeneity of current classification practice in which underlying health conditions are documented by syndromes, categories, or disease entities. The use of codes from ICF domains would promote a standard basis for documentation as well as clarify the information provided by syndromes and diseases entities. Related to the above recommendations for use of ICF codes in documenting health conditions and functional limitations of children is the need to use a common qualifier for the severity of disability across survey, clini-

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Workshop on Disability in america A new look: Summary and background papers TABLE C-2 Examples of ICF Activities and Participation Codes for Key Indicators   Codes for the following age groups Activity 0–2 yr 3–5 yr 6–11 yr 12–17 yr Mobility d420, transferring oneself d455, moving around d470, using transportation d470, using transportation Communication d315, receiving nonverbal messages d330, speaking d350, conversation D355, discussion Self-care d550, eating d530, toileting d540, dressing d570, looking after ones health Learning d120, other purposeful sensing d140, learning to read d175, solving problems d177, making decisions Social interactions d7601, child-parent relationships d710, basic interpersonal relationships d750, informal social relationships d740, formal relationships

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Workshop on Disability in america A new look: Summary and background papers cal, and research applications. Although the variability found in current prevalence data is no doubt attributable to different definitions used in surveys and service reports, the use of a severity qualifier in some studies and not others is also likely to be a significant source of variability. The adoption of a common qualifier for severity is important to enhance the comparability of data gathered in different surveys. It should also improve correspondence of survey data with documentation provided in the context of systems such as, health services, social security and special education. Although this recommendation has been proposed in the context of the ICF, its consideration is not contingent upon the use of the ICF but is applicable for any form of documentation. Another area of potential application is the use of the ICF-CY taxonomy for the alignment of content for a new generation of developmentally appropriate instruments. Finally, ICF-CY may serve as a reference for the identification of concise indicators for surveys (McDougall and Miller, 2003; Hutchison and Gordon, 2005). Adoption of ICF-CY as the standard for defining and classifying disability can serve as a unifying mechanism and a common language for the provision of services for children and youth everywhere. In the continuing effort to improve policy and practice on behalf of children with disabilities, the admonition stated by Hobbs thirty years ago is still timely: “classification is serious business. Classification can profoundly affect what happens to a child. It can open doors to services and experiences the child needs to grow in competence, to become a person sure of his worth, and appreciate the worth of others, to live with zest and to know joy” (Hobbs, 1975b, p.1). REFERENCES Aron, L.Y., Loprest, P.J., and Steuberle, C.E. (1996). Serving Children with Disabilities: A Systematic Look at the Programs. Washington, DC: Urban Press. Baum, J.D. (1977). The continuum of caretaking casualty. Developmental Medicine & Child Neurology 19(4):543–544. Capute, A.J. and Palmer, F.B. (1980). A pediatric overview of the spectrum of developmental disabilities. Journal of Developmental and Behavioral Pediatrics 1:66–69. Capute, A.J., Shapiro, B.K., and Palmer, F.B. (1981). Spectrum of developmental disabilities: continuum of motor dysfunction. Orthopedic Clinics of North America 12(1):3–22. Costello, E.J., Angold, A., Burns, B.J., Erkanli, A., Stangl, D.K., and Tweed, D.L. (1996). The Great Smoky Mountains Study of Youth. Functional impairment and serious emotional disturbance. Archives of General Psychiatry 53(12):1137–1143. Costello, J., Mustillo, S., Erkanli, A., Keeler, G., and Angold, A. (2005). Prevalence and development of psychiatric disorders in childhood and adolescence. Archives of General Psychiatry 60:837–844. Down, J.L. (1887). Abstracts of the Lettsomian lectures on some of the mental affections of childhood and youth. British Medical Journal 8:49–50.

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Workshop on Disability in america A new look: Summary and background papers Eaton, W.W., Mortensen, P.B., Thomsen, P.H., and Frydenberg, M. (2001). Obstetric complications and risk for severe psychopathology in childhood. Journal of Autism and Developmental Disorders 31(3):279–285. Fedeyko, H. J. and Lollar, D.J. (2003). Classifying disability data: a fresh, integrative perspective. In B.M. Altman, S.N. Barnartt, G.E. Hendershot and S.A. Larson (Eds.) Using survey data to study disability: results from the National Health Interview Survey on Disability. Research in Social Science and Disability 3:55–72. First, M.B. and Pincus, H.A. (2002). The DSM-IV text revision: rationale and potential impact on clinical practice. Psychiatric Services. 53(3):288–292. Forfar, J.O., Hume, R., McPhail, F.M., Maxwell, S.M., Wilkinson, E.M., Lin, J.P., and Brown, J.K. (1994). Developmental Medicine & Child Neurology 36(12):1037–1048. Forsyth, D. (1915). The development of children. British Medical Journal. March 20, pg. 535. Grill, E., Ewert, T., Chatterji, S., Kostanjsek, N., and Stucki, G. (2005). ICF core sets development for the acute hospital and early post-acute rehabilitation facilities. Disability and Rehabilitation 27(7–8):361–366. Halfon, N. and Newacheck, P. (1999). Prevalence and impact of parent reported disabling mental health conditions among U.S. children. Journal of the American Academy of Child and Adolescent Psychiatry 38(5):600–609. Hobbs, N., ed. (1975a). Issues in the Classification of Children. San Francisco, CA: Jossey Bass. Hobbs, N. (1975b). The Futures of Children. San Francisco, CA: Jossey Bass. Hogan, D.P., Msall, M.E., Rogers, M.L., and Aver, R.C. (1997). Improved disability estimates of functional limitations among American children aged 5–17. Maternal Child Health Journal 1(4):203–216. Hughes, D., Halfon, N., Brindis, C., and Newacheck, P. (1996). Improving children’s access to health care: the role of decategorization. Bulletin of the New York Academy of Medicine 73:237–254. Hutchison, T., and Gordon, D. (2005). Ascertaining the prevalence of childhood disability. Child: Care Health and Development 31(1):99–107. Inhelder, B. (1966). Cognitive development and its contributions to the diagnosis of some phenomena of mental deficiency. Merrill Palmer Quarterly 11:299–311. Inhelder, B. (1968). The Diagnosis of Reasoning in the Mentally Retarded. New York: John Day. Kaplan, D. (2000). The definition of disability: perspective of the disability community. Journal of Health Care Law and Policy 3(2):352–364. Landsman, G. (2005). Mothers and models of disability. Journal of Medical Humanities 26(2/3):121–139. LaPlante, M. and Carlson, D. (1995). Disability in the United States. Prevalence and Causes, 1992. Report of the Disability Statistics Rehabilitation Research and Training Center. Washington, DC: National Institute on Disability and Rehabilitation Research. Lollar, D.J. and Simeonsson, R.J. (2005). Diagnosis to function: classification for children and youths. Journal of Developmental and Behavioral Pediatrics. 26(4):3323–330. Marks, D. (1997). Models of disability. Disability and Rehabilitation 19(3):85–91. McDougall, J. and Miller, L.T (2003). Measuring chronic health condition and disability as distinct concepts in national surveys of school-aged children in Canada: a comprehensive review with recommendations based on the ICD-10 and ICF. Disability and Rehabilitation 25(16):922–939. Mudrick, N.R. (2002). The prevalence of disability among children: paradigms and estimates. Physical Medicine and Rehabilitation Clinics of North America. 13:775–792.

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Workshop on Disability in america A new look: Summary and background papers Munn, P. (1997). Models of disability for children. Disability and Rehabilitation 19(11):484–486. Narrow, W.E., Regier, D.A., Goodman, S.H., Rae, D.S., Roper, M.T., Bourdon, K.H., Hoven, C., and Moore, R. (1998). A comparison of federal definitions of severe mental illness among children and adolescents in four communities. Psychiatric Services 49(12):1601–1608. Newacheck, P. and Halfon, N. (1998). Prevalence and impact of disabling chronic conditions in childhood. American Journal of Public Health 88(4):600–607. Newacheck, P., Halfon, N., Brindis, C.D., and Hughes, D.C. (1998). Evaluating community efforts to decategorize and integrate financing of children’s health services. Milbank Quarterly 76(2):57–73. Ounsted, M. (1987). Cause, continua and other concepts. I. The “continuum of reproductive casualty.” Paediatric & Perinatal Epidemiology 1(1):4–7. Pasamanick, B., and Knobloch, H. (1966). Retrospective studies on the epidemiology of reproductive casualty: old and new . Merrill-Palmer Quarterly 12:7-26. Roosa, M.W., Fitzgerald, H.E., and Carlson, N.A. (1982). Teenage parenting and child development: a literature review. Infant Mental Health Journal 3(1):4–18. Sameroff, A.J. and Chandler, M.J. (1975). Reproductive risk and the continuum of caretaking casualty. In F.D. Horowitz, M. Hetherington, S. Scarr-Salapatek, and G. Siegel, eds. Review of Child Development Research. 4:187–244. Chicago: University of Chicago Press. Schalick, W.O. (2000). Children, disability and rehabilitation in history. Pediatric Rehabilitation 4(2):91–95. Simeonsson, R.J. and Rosenthal, S.L. (2001). Developmental models and clinical practice. In C. E. Walker and M. C. Roberts, Eds. Handbook of Clinical Child Psychology, 3rd ed. New York: Wiley. Simeonsson, R.J., Lollar, D., Hollowell, J., and Adams, M. (2000). Revision of the International Classification of Impairments, Disabilities and Handicaps: developmental issues. Journal of Clinical Epidemiology 53:113–124. Simeonsson, R.J., Leonardi, M., Bjorck-Akesson, E., Hollenweger, J., and Lollar, D. (2003). Applying the International Classification of Functioning Disability and Health to measure childhood disability. Disability & Rehabilitation 25(11–12):602–610. Smyke, A.T., Dumitrescu, B.A., and Zeanah, C.H. (2002). Attachment disturbances in young children. I. The continuum of caretaking casualty. Journal of the American Academy of Child & Adolescent Psychiatry 41(8):972–982. SSA (Social Security Administration). (2005). Disability Evaluation under Social Security. Office of Disability Programs, Social Security Administration. Washington, DC: Social Security Administration. Stein, R.E. and Silver, E.J. (1999). Operationalizing a conceptually based noncategorical definition: a first look at US children with chronic conditions. Archives of Pediatric and Adolescent Medicine 153 (1):68–74. Stein, R.E. and Silver, E.J. (2002). Comparing different definitions of chronic conditions in a national data set. Ambulatory Pediatrics 2(1):63–70. Stein, R.E., Bauman, L.J., Westborrok, L.E., Coupey, S.M. and Ireys, H.T. (1993). Framework for identifying children who have chronic conditions: the case for a new definition (special article). J. Pediatrics 122:342–347. Verbrugge, L. and Jette, A. (1994). The disablement process. Social Science and Medicine 38(1):1–14. Wells, T. and Hogan, D. (2003). Developing concise measures of childhood activity limitations. Maternal and Child Health Journal 7(2):115–126.

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Workshop on Disability in america A new look: Summary and background papers Westbrook, L.E., Silver, E.J., and Stein, R. E. K. (1998). Implications for estimates of disability in children: a comparison of definitional components. Pediatrics 101(6):1025–1030. WHO (World Health Organization) (2001). International Classification of Functioning, Disability and Health. Geneva, Switzerland: World Health Organization. Zigler, E. (1969). Developmental versus difference theories of retardation and the problem of motivation. American Journal of Mental Deficiency 73:536–556.