Chapter 6
Differential Diagnosis

Differential diagnosis refers to the process by which a clinically significant problem or set of symptoms is evaluated and distinguished from other conditions, usually associated with similar clinical features. In the case of mental retardation, many neurodevelopmental and psychiatric disorders can mimic or accompany the mental retardation diagnosis. These other disorders may also be independent grounds for Supplemental Security Income (SSI) and Disability Income (DI) benefits eligibility. It is often challenging for the Social Security Administration (SSA) disability determination specialist to distinguish between mental retardation and other neurodevelopmental and psychiatric disorders with similar signs and symptoms. In addition, when these other disorders are present in addition to mental retardation, they may make assessment of intellectual and adaptive functioning even more complicated than it frequently is. In such cases, it is imperative that clinical



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Mental Retardation: Determining Eligibility for Social Security Benefits Chapter 6 Differential Diagnosis Differential diagnosis refers to the process by which a clinically significant problem or set of symptoms is evaluated and distinguished from other conditions, usually associated with similar clinical features. In the case of mental retardation, many neurodevelopmental and psychiatric disorders can mimic or accompany the mental retardation diagnosis. These other disorders may also be independent grounds for Supplemental Security Income (SSI) and Disability Income (DI) benefits eligibility. It is often challenging for the Social Security Administration (SSA) disability determination specialist to distinguish between mental retardation and other neurodevelopmental and psychiatric disorders with similar signs and symptoms. In addition, when these other disorders are present in addition to mental retardation, they may make assessment of intellectual and adaptive functioning even more complicated than it frequently is. In such cases, it is imperative that clinical

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Mental Retardation: Determining Eligibility for Social Security Benefits evaluations take these complex factors into consideration and draw conclusions based on objective data and best clinical practice. This chapter focuses on the challenges likely to be encountered in determining eligibility for SSI and DI benefits through a diagnosis of mental retardation. As outlined in earlier chapters, especially Chapter 2, the accuracy of the diagnosis of mental retardation is crucial both to SSA and to the client: to the former so that it can carry out its mandate, and to the latter for essential income support and as a gateway to other needed entitlements. While earlier chapters dealt with issues related to defining mental retardation and to the diagnostic criteria for this condition, here we consider distinguishing mental retardation from other conditions. In addition, we review circumstances that can complicate the process of assessment and discuss pertinent issues in evaluating intellectual and functional status across the life span. The prevalence of mental retardation is highest among school-age populations (e.g., Kiely, 1987; Larson et al., 2001) and, by definition, its symptoms must be present before adulthood, though actual diagnosis may not take place until after schooling ends. Depending on their state of residence, between 5.2 and 11.5 percent of all children attending public schools are currently classified as having a disability (not necessarily mental retardation) of sufficient severity to receive special services (U.S. Department of Education, 1994, Table AA25). However, eligibility for special services in school does not necessarily confer eligibility for SSI benefits. Most individuals with a diagnosis of mental retardation who receive special education services become gainfully employed once they leave the school system. There is, however, an increased probability that individuals in this population may need financial support at some time during their adult lives. Mental retardation is a prevalent disability among the population receiving special education services, but substantial numbers of these individuals will have some other condition associated with varying degrees of disability, including developmental, learning, sensory, motor, or psychiatric disability. These conditions produce a wide range of impairments, and to a greater or lesser degree can share signs or symp-

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Mental Retardation: Determining Eligibility for Social Security Benefits toms with mental retardation. It is important to determine the nature of each individual’s limitations in order to develop plans for education, habilitation, and vocational training, as well as for making SSI eligibility determinations. CLINICAL CONSIDERATIONS AND ELIGIBILITY DETERMINATION To arrive at a correct diagnosis or case classification, clinicians evaluate the client’s signs and symptoms and compare them to those of other similar conditions. Additional information is then gathered to rule out possibilities systematically until a valid diagnosis can be made. Symptoms refer to the concerns expressed by the affected individual or his or her representatives, while “signs” are objective findings from a physical examination, laboratory tests, psychological assessment, or educational evaluation. In the case of mental retardation, presenting signs and symptoms are usually evident and associated with underlying intellectual and adaptive impairments. Nevertheless, differential diagnosis can be complicated by at least four other factors. First, the severity and nature of impairments can vary substantially, with each person having his or her own strengths and weaknesses in performance. Thus, clinical presentation may be different among affected individuals, some of whom have abilities that are only subtly different outside the classroom setting from those of people without mental retardation. Second, the specific manifestations of mental retardation change with development throughout the life span. In less severe cases, it is difficult to be confident about a diagnosis made during infancy or early childhood, yet assessment is rarely conducted for clients after they leave school. Third, other conditions can produce signs and symptoms very similar to those of mental retardation, especially before elementary school begins. These include other developmental, learning, sensory, and motor impairments. In adolescence or young adulthood, psychiatric impairments may become increasingly evident, further compli-

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Mental Retardation: Determining Eligibility for Social Security Benefits cating determinations of mental retardation or even exacerbating its effects. Finally, there are a number of other conditions that can complicate assessment and make it difficult to determine whether a diagnosis of mental retardation actually is an underestimation of a person’s true capabilities. These issues are all reviewed in this chapter, with particular attention to their significance in the context of eligibility for SSI and DI. Eligibility for Support It is sometimes difficult to distinguish between mental retardation and other conditions currently covered by SSI, the so-called categorical disorders: autism, learning disability, borderline intellectual functioning, and organic mental disorders marked by specific behavioral phenotypes. It is particularly important to make these distinctions when selecting treatments and developing plans for education, habilitation, and vocational training. Diagnostic information is used in making very different types of decisions in clinical, educational, vocational, and SSI contexts. In educational settings, it is critical to determine if a condition other than mental retardation (like a specific learning disability or sensory, motor, or psychiatric impairment) is causing or contributing to poor performance. These differential diagnoses have direct implications for developing individualized plans of treatment and instruction to encourage learning. In clinical settings, arriving at the correct differential diagnosis determines appropriate and effective treatment and prevention strategies. In the SSI context, the explicit focus is on eligibility for support— that is, current employability for adults and marked or severe limitations in developmental skills for children. For SSI eligibility, the underlying cause or origin of intellectual or functional impairment is not important if the individual meets the income criteria and intellectual disability definitions for mental retardation. Eligibility is dependent on the severity of impairment regardless of its source. Therefore, the primary goal of a diagnosis differentiating between mental retardation

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Mental Retardation: Determining Eligibility for Social Security Benefits and some other condition is not relevant when the severity of disability clearly meets or exceeds eligibility criteria within SSA guidelines. This would include situations in which either the total IQ test score is less than 60 or the individual has another condition that is so disabling that it interferes with the determination of true intelligence, such as blindness, deafness, uncontrolled seizures, cerebral palsy, or some other disorder. Similarly, once eligibility for SSI benefits for individuals with mental retardation is determined, the decision process does not need to consider additional comorbid disorders, and the process of differential diagnosis need not continue further. Differential diagnosis is a different matter for individuals having less severe disabilities that put them at the border of SSI eligibility criteria. For individuals with mild mental retardation, it is vitally important to generate a complete description of signs and symptoms, including diagnosis of comorbid conditions, as well as an accurate assessment of intellectual and functional status. Furthermore, the presence of additional disabilities in such cases can impair functioning to such an extent that competitive employment is unlikely or even impossible. For cases having less severe clinical presentations, carefully conducted evaluation procedures that include standardized assessments of intellectual development and adaptive function (see Chapters 3 and 4) can usually provide the accurate estimates of capabilities needed in arriving at a valid differential diagnosis, except perhaps for very young children. Currently, SSA defines mental retardation by quantitative rather than qualitative performance criteria relative to age-referenced expectations. This is incorporated into SSA regulations, which include extended discussions of assessment methods and criteria that vary with age and with respect to broad domains of functioning. SSA has deliberately built some flexibility into its procedures for determining SSI eligibility at various chronological ages (Social Security Administration, 2000), but the clinician must recognize the strengths and limitations of assessment tools at each stage of development. Evaluators must be sensitive to the diagnostic precision of the instruments em-

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Mental Retardation: Determining Eligibility for Social Security Benefits ployed, aware of the types of errors that imprecision may introduce, and be able to access sources of additional information that can reduce the likelihood of misclassification. These issues are discussed at length in Chapters 2 and 3. Individuals can qualify for SSI in two ways. The first and most obvious is by having a condition listed by the SSA as eligible by definition. Two lists define conditions that meet the standard for severity; one applies to both children and adults and the other list is for use with children under 18 years of age. These lists are intended to objectify and facilitate the determination process, but problems can arise because, as pointed out in earlier chapters, the clinical definitions of mental retardation provided in authoritative references (e.g., Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition—DSM-IV—American Psychiatric Association, 1994), are not the same as the criteria provided in the SSA listing. Because of this disparity, some individuals with a clinical diagnosis of mental retardation do not meet SSI eligibility criteria. SSI eligibility is intentionally limited to only those individuals whose disability is severe enough to impose substantial restrictions on their ability to work, either now or in the future. Individuals can qualify for SSI support in a second way: they are eligible if their status is functionally equivalent to a listed condition. In the case of mental retardation, functional equivalence for children is assessed in six domains: (1) acquiring and using information, (2) attending and completing tasks, (3) interacting and relating with others, (4) moving about and manipulating objects, (5) caring for oneself, and (6) health and physical well-being (Social Security Administration, 2000). To meet functional equivalence criteria, the child must have either marked impairment (equal to or greater than 2 but less than 3 standard deviations below the mean on a standardized, norm-referenced assessment) in two domains, or extreme impairment (equal to or greater than 3 standard deviations below the mean) in a single domain. While this second path to eligibility offers children having unrecognized mental retardation an opportunity to obtain needed sup-

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Mental Retardation: Determining Eligibility for Social Security Benefits port, this opportunity rests to a substantial degree on the judgment of the examiner. Therefore, the use of uniform, valid procedures and criteria are essential for cases falling into this category, as well as for similar situations with adults. Issues Associated with Life Span Development Age-related considerations are crucial in making a diagnosis of mental retardation because key signs and symptoms, as well as appropriate assessment methods, are quite different across the life span. Abilities and socially appropriate expectations change dramatically with development, and these factors can complicate the evaluation process in distinct, age-specific ways. Because adaptive behavior changes and tends to increase with age (e.g., Hundert et al., 1997), most measures of adaptive behavior are structured so that items are presented in a developmental sequence. Declines in adaptive behavior can be associated with advanced aging, as it is in the general population, or at an earlier chronological age in the instance of some disorders, like Down syndrome (Kapell et al., 1998; Zigman et al., 1996), or in the presence of severe to profound mental retardation. Moreover, although there are systematic differences in the typical adaptive performance of people with mild mental retardation and their peers with more severe degrees of mental retardation, there is also overlap in adaptive behavior skills among people assessed with differing degrees of intellectual disability (Janicki & Jacobson, 1982). For example, it is possible for someone with mild mental retardation to have certain adaptive behavioral skills that are less advanced than those of another person with moderate mental retardation. These differences may reflect different experiences, opportunities, and participation in services. The following sections use four stages of maturation to identify and discuss key factors in making the differential diagnosis of mental retardation and determining SSI eligibility.

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Mental Retardation: Determining Eligibility for Social Security Benefits INFANTS, TODDLERS, AND PRESCHOOLERS The limitations of current assessment technologies are a major problem in evaluating disability in very young children. Advances are being made rapidly, especially in identification of genetic conditions likely to increase risk, but diagnosis of mental retardation remains difficult except in cases with clear biomedical manifestations or severely delayed development. This is especially true until the age when language delays can be documented, or even later when academic achievement is regularly evaluated. For children under age 3, a developmental quotient (developmental age/chronological age × 100) may serve as a surrogate for standard IQ, such that quotients of less than 67 define marked impairment and quotients less than 50 define extreme impairment (Social Security Administration, 2000). This approach is currently considered to be the best available diagnostic practice, but it has limited predictive validity and precision. The distinction between generalized and specific delays, both of which can have an impact on function to a degree that will quality for SSI, often has to be postponed until later ages. In preschoolers, language impairment is the most commonly identified specific developmental disorder. In principle, specific language impairment is distinguished from mental retardation by the relative preservation of nonlanguage skills. However, both conditions are frequently associated with social and behavioral deficits, and both are strong predictors of poor academic achievement at older ages (McArthur et al., 2000). Therefore, specific language impairment can be difficult to distinguish from mild mental retardation, as the following case illustrates. Allen is a 3-year-old who has been referred for delayed language development. He was born at full term following an uncomplicated pregnancy. He is a healthy child whose early developmental milestones were achieved on time or only slightly delayed with the exception of language. He started speaking single words at 18 months of age, began using baby talk at 21 months and did not start speaking in phrases until recently. Allen waved “bye-bye” before his first birthday, knew some of his body

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Mental Retardation: Determining Eligibility for Social Security Benefits parts by 24 months, and follows some multistep commands. He likes to play and roughhouse with his 4-year-old brother. His hearing has been tested and found to be normal. His rate of language development has been approximately two-thirds of normal expectations. On formal evaluation he was found to be functioning in the low borderline range of intelligence but he showed clear unevenness in his results. Language abilities were in the deficient range, while problem solving abilities were in the borderline range. With this developmental profile, it is difficult to distinguish between specific language impairment or mild mental retardation. Early intervention should target development of language and general intellectual functioning, with frequent follow-up evaluations (at approximately six-month intervals) to monitor progress and refine diagnosis. In Allen’s case, uncertainty regarding differential diagnosis can be resolved in a year or two when he can be given a detailed assessment that focuses on both language development and intelligence, but in many similar cases, diagnostic evaluations will be delayed until early in the child’s schooling. In contrast to the severe constraints on the ability to diagnose mild mental retardation in young children, a great deal is now known about the conditions associated with increased risk for mental retardation. Babies born prematurely, very small for their gestational age, or exposed in utero to alcohol or other teratogenic agents are at increased risk of mental retardation. Babies are also at risk if their mothers are in their young teens, have a history of poor prenatal care, have less than a high school education, or are living in poverty (e.g., Sameroff, 1986). With particular relevance to SSI determination, many of these risk factors are also associated with economic disadvantage. However, while large numbers of young children are at risk, the majority of them do not have mental retardation. Current research is focusing on refining the ability to identify those children who will, in fact, develop atypically. Accumulating evidence suggests that intervention may be most effective if it is initiated as early as possible, although there is still debate in the professional and scientific community on this point (Bailey et

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Mental Retardation: Determining Eligibility for Social Security Benefits al., 1999; Ramey & Ramey, 1999). Therefore, public health policy needs to weigh the relative value of providing earlier supports to an expanded subpopulation, only a subset of whom will prove to have a substantial disability, against the effect of delaying supports and treatments for a more limited number of individuals who may then need more intensive interventions over a longer period of time. A prime example of this dilemma has been highlighted in the field of autism, in which early, intensive treatment has produced a range of positive outcomes; for some children, the results of treatment have been dramatic (Lovaas, 1987; National Research Council, 2001; Rogers, 1998). Recent neuropsychological and neurobiological evidence also supports the hypothesis of a window of opportunity for intervention effectiveness in very young children at risk for mental retardation and other developmental disabilities (Bailey et al., 1999). There are several categorical disorders that are likely to be encountered while evaluating very young children with suspected mental retardation. The disability examiner must determine whether intellectual or adaptive deficits are due to retardation or aspects of these other conditions. Autism and Pervasive Developmental Disorders John is a 4-year-old with delayed language and social skills development. Parents report that John is “in his own world” and has limited spontaneous speech, although he frequently repeats back exactly what is said to him. He has other unusual behaviors. These include toe walking, hand flapping, and excessive spinning of the wheels on his toy truck. John has excellent puzzle-solving skills, but he does poorly with changes in routine and seems most content when he is entertaining or playing by himself for long periods of time. During formal testing, John often seemed inattentive and his obtained total test score (IQ) of 55 on the Stanford-Binet, Fourth Edition, would seem to be an underestimate of his true intelligence. Autism, currently classified as a pervasive developmental disorder

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Mental Retardation: Determining Eligibility for Social Security Benefits with symptoms that are present by 3 years of age, classically involves disturbances of: (1) social interaction, (2) communication, and (3) behavior. Autism differs from mental retardation in that intellectual deficits may or may not be apparent, but social, communication, and behavior disorders are always noted. Difficulties with social interactions include avoidance of eye contact during social activities, difficulty developing peer relations, excessive self-directed play, or avoidance of shared activities. Communication deficits may include unusual speech prosody (e.g., atypical intonation, cadence, or inflection; immediate or delayed echolalia; perseveration; lack of spontaneous speech; or difficulty with pragmatic language initiation). Behavior difficulties noted in autism include repetitive stereotypies (e.g., hand flapping, toe walking, rocking); extreme difficulties with changes in routine; and limited imaginative play or preoccupation with parts of toys (e.g., spinning the wheels of a truck rather than imaginative play with the whole truck) (American Psychiatric Association, 1994; Stone, 1997; Volkmar et al., 1994, 1997, 1999; Wolraich et al., 1996). A recent review of 23 surveys focusing on autism and including over 4 million individuals reported a median prevalence of 5.2 per 10,000 population (95 percent confidence interval 4.5-5.5 per 10,000; Fombonne, 1999). Prevalence rates appear to have increased in recent years, presumably due to improved early identification and changes in case definition, but additional research is needed to confirm this. On average, there are 3.8 times as many males as females with autism (Fombonne, 1999). Distinguishing whether mental retardation is present in individuals with autism is challenging, due in part to limitations in communication skills and social interaction deficits of the affected individuals (Arnold et al., 2000), as well as the diverse etiological and symptomatic expressions of the disorder. Nevertheless, Fombonne (1999) recently reported that an estimated 80.3 percent of 1,533 children with autism also had mental retardation. Estimates indicated that approximately 29 percent had mild to moderate mental retardation and 42 percent had severe to profound mental retardation. While the overall propor-

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Mental Retardation: Determining Eligibility for Social Security Benefits system each year. This highlights the fact that there is a substantial population of adults who, at least at some time, had a recognized intellectual impairment with a substantial impact on their achievement. Virtually everyone with more severe mental retardation will have been identified appropriately by the time they reach adulthood. In these cases, differential diagnosis should no longer be an issue for determination of SSI eligibility. However, the situation is very different for adults with milder forms of mental retardation and for younger adults. Young adults who have recently turned 22 and left public high school should have recently been assessed to develop a transition plan to identify their work-related skills and to arrange for the involvement of another social service system once they depart public school. For example, regional centers were created in California to provide continuing services and supports. This system provides opportunities for state agencies responsible for follow-through services with these adults to evaluate each individual’s status vis-à-vis SSI criteria for eligibility and establish a record that could be useful for SSA staff should an application for support be made at a future date. For older adults with mild mental retardation, who have long since left high school, the situation is quite different. Many have probably vanished from the service delivery system, in part because the formal structure of educational settings that encourages systematic assessment is no longer available. Evaluation of academic skills and any other formal testing is unlikely to occur in the normal course of adult activities, and therefore there will be no opportunity to document intellectual impairment. This is especially problematic for older adults who come from families eligible for SSI support based on economic considerations, given their tendency to have limited access to services, as in the following case. Marlene is a 36-year-old woman with mild mental retardation living in the community with her parents. Marlene completed high school 18 years ago after struggling through regular and special education classes. Transition activities were not yet part of the school curriculum, and therefore she did not receive any vocational, social, or daily living skills training. Once Marlene exited school, she remained at home with her parents

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Mental Retardation: Determining Eligibility for Social Security Benefits and received no outside assistance as she sought employment. Since then, Marlene’s parents, despite their own economic hardships, have continued to take care of her everyday needs, so they never were concerned about her lack of independence. Marlene has floated in and out of sheltered workshop settings but never found her niche. Her parents are now reaching ages when they are increasingly concerned about who will care for their daughter when they are no longer able to meet her needs. Marlene does not have any marketable job skills, and although her parents are very worried, they are doing little at the present time to plan for their daughter’s future. Adults with mental retardation who become economically independent of their families may become eligible for SSI supports themselves. If they have IQs below 60, these individuals would qualify for SSI support virtually without exception, as long as they have problems obtaining or maintaining employment. In these cases, the issues relevant to differential diagnosis are comparable to those mentioned for the school-age population with severe impairments. However, for more mildly affected individuals, there is a reasonable likelihood that they will have received a diagnosis other than mild mental retardation earlier on, and so they will not have established their eligibility for benefits under the mental retardation categorical listing. Especially careful assessment and consideration of functional equivalence will be required of the disability determination specialist to determine the eligibility of such an individual. Considerations of psychiatric impairment or a dual diagnosis, as delineated fully in the section on adolescents, apply to adults with mental retardation as well. However, there are several additional challenges, particularly for older adults who left high school prior to 1990 and the initiation of the concept of transition planning. One is finding adults with disabilities once they have left the school system and no longer bear a school-based classification (e.g., mild mental retardation, learning disability). The second challenge is to ensure that these individuals get a complete reassessment in order to determine their eligibility for SSI. This is imperative, given evolving definitions of mental

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Mental Retardation: Determining Eligibility for Social Security Benefits retardation and developmental disability, as well as classification practices (MacMillan et al., 1998). Finally, adult sons and daughters of non-English-speaking parents may not routinely come to the attention of disability examiners. If these individuals have not participated in special education during their school years, they may be invisible to the service systems until some unanticipated event forces the need for direct support. ADDITIONAL CONSIDERATIONS Cultural Issues In developing the differential diagnoses for mental retardation, it is important to ensure that assessment instruments are culturally appropriate for the individual being evaluated (Sattler, 1988; Witt et al., 1998) and to clarify the relationship between culture and achievement as much as is feasible (Gallimore & Goldenberg, 2001). In addition to the influence of the majority culture and the English language, some standardized intelligence and adaptive behavior tests require social knowledge that may not be relevant in a given minority culture (Golden, 1990). Recent attempts to develop standardized tests of intelligence and adaptive behavior that are not culturally biased are described in Chapters 3 and 4. In developing a differential diagnosis for mental retardation, particularly mild retardation, examiners need to determine whether evident psychopathological conditions are related to a specific cultural process. For example, Asian families may believe that emotional problems like anxiety bring shame and guilt to the family, and so may not disclose them (Cuellar & Paniagua, 2000). Paniagua (1998) has pointed out that, in some Hispanic cultures, mental or physical problems in a child may be thought to be the result of an extremely frightening or startling experience. These, as well as other attributions about the behaviors of their children with mental retardation (Chavira et al., 2000), can obscure the presence of a dual diagnosis or lead to a diagnosis other than mental retardation.

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Mental Retardation: Determining Eligibility for Social Security Benefits Clearly, examiners should be sensitive to the beliefs, attitudes, and practices related to a specific culture or religion that might be compatible or incompatible with assessment methods, employment interventions, and prioritization of goals (McAdoo, 1995; Rogers-Dulan & Blacher, 1995). In Hispanic families, for example, cultural values of family cohesion may conflict with policies promoting community inclusion and independent employment of persons with mental retardation, especially in integrated settings (Blacher et al., 1997). Specific Disorders Associated with Mental Retardation A complete differential diagnosis of mental retardation should address all possible disorders that share similar signs and symptoms with mental retardation. Consideration of the cause of an individual’s intellectual disability may be important for treatment and counseling. Classification systems have emphasized both function (behavior) and etiology (biomedical) dimensions since the early 1960s (e.g., Heber, 1961). However, the importance of establishing the cause of disability has not been a major focus of this chapter because it is not one of SSA’s priorities for this study. Since discussion of specific disorders associated with mental retardation may assist SSA eligibility determination specialists in evaluating individuals applying for SSI under the diagnosis of mental retardation, they are described briefly here. Many of the issues that complicate functional and cognitive assessment or limit functional diagnostic precision, especially in infants, toddlers, and preschoolers, have already been discussed. These are serious concerns that could, at least in some cases, be addressed by refocusing attention to the underlying causes of mental retardation. There is currently an explosion of knowledge in the biomedical sciences, especially genetics and neuroscience, and this is allowing a constantly expanding diagnostic capability. Innovative technologies are now available to determine if conditions frequently associated with mental retardation are or are not present, and while their presence does not always result in substantial disability, failure to achieve eco-

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Mental Retardation: Determining Eligibility for Social Security Benefits nomic self-sufficiency may be the rule rather than the exception. Therefore, as in the case of Down syndrome, SSA might consider including conditions with a high probability of causing mental retardation or some other substantial disability in its list of conditions eligible for SSI benefits. Of course, some affected individuals will achieve economic self-sufficiency and will therefore be ineligible, but if an individual with mental retardation encounters difficulties in obtaining or maintaining employment, it seems reasonable to presume that the underlying impairment contributed significantly to the situation. Mental retardation can be associated with genetic as well as nongenetic causes. Therefore, we have provided a brief overview of these broad categories of conditions and illustrated the issues that can arise in SSA eligibility determination for two representative conditions, Prader-Willi syndrome (genetic) and fetal alcohol syndrome (nongenetic). Genetic Conditions There are over 750 known genetic causes of mental retardation. Collectively, these may account for as many as one-third of all cases of mental retardation (Matilainen et al., 1995; Opitz, 1996). Historically, identifiable genetic disorders were thought to cause severe to profound mental retardation, but more recent estimates suggest that 10 to 50 percent of mild mental retardation may also have a specific genetic origin (Rutter et al., 1996). Nonspecific genetic factors associated with individual differences in intelligence, another topic of considerable contemporary debate (e.g., Neisser, 1998), are not discussed here. Among the relatively few disorders that have been studied to date, variability in impact on cognitive and adaptive functioning has been noted. Thus, IQ levels in individuals with disorders like fragile X syndrome, Williams syndrome, velo-cardio-facial syndrome and Prader-Willi syndrome can range widely (see Dykens et al., 2000 for a review). Like their counterparts with severe disabilities, however, high-functioning persons with these and other syndromes are likely to have char-

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Mental Retardation: Determining Eligibility for Social Security Benefits acteristics that compromise their employability (e.g., intellectual impairments, specific maladaptive behaviors, or psychiatric disorders). Prader-Willi syndrome is perhaps best known for its association with eating disorders. Whereas affected babies invariably have pronounced feeding difficulties, they typically develop hyperphagia and food-seeking behaviors (e.g., foraging and hoarding) during early childhood (Dykens & Cassidy, 1999). Without lifelong dietary management, affected individuals invariably become morbidly obese and weight-associated complications remain the leading cause of death for people with this syndrome. While the vast majority of people with Prader-Willi syndrome are invariably preoccupied with eating and food, some also show a host of nonfood obsessions and compulsive behaviors, suggesting increased risk of full-blown obsessive-compulsive disorder in this population (Dykens et al., 1996). Persons with Prader-Willi syndrome also have adaptive skills that typically fall considerably below their measured IQ (Dykens et al., 1992). Compared with others with mental retardation, children and adults with Prader-Willi syndrome show high rates of temper tantrums, aggression, stubbornness, underactivity, excessive daytime sleepiness, and emotional lability (Dykens & Kasari, 1997; Dykens & Smith, 1998; State et al., 1999). Approximately 32 percent of people with the disorder have IQs of 70 or higher. Nevertheless, higher IQ individuals are extremely likely to have poor adaptive behavior and show the same behavioral and food-related vulnerabilities as their peers with lower IQs. Regardless of their IQs, persons with Prader-Willi syndrome share the same needs for intensive support. In the employment arena, most adults with Prader-Willi syndrome are not employed competitively, and low job retention is invariably associated with aggression, tantrums, and compulsive food-seeking (Dykens, 2002). In light of these findings, several states have now passed legislation that deems any person with a confirmed genetic diagnosis of Prader-Willi syndrome eligible for lifelong state services regardless of his or her IQ. This may be an effective model for the SSA classification process to adopt.

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Mental Retardation: Determining Eligibility for Social Security Benefits Nongenetic Conditions Mental retardation can also be associated with a variety of causes that are nongenetic in origin. Among them are: (a) infections and parasitic diseases (e.g., congenital rubella syndrome, encephalitis), (b) deficiency diseases (e.g., congenital iodine deficiency syndrome), (c) congenital malformations (e.g., hydrocephalus), (d) neuroteratogenic exposure (e.g., fetal alcohol syndrome), (e) mechanical injury (e.g., perinatal hypoxia, traumatic brain injury), and (f) environmental deprivation. Of course, this is not an exhaustive listing, and for this discussion it is important to note only that each of these conditions can vary in its functional impact. In some cases, there may be minimal or no long-term consequences of the condition, while profound and permanent impairments may be observed in others. When the presence of one of these conditions is documented in an individual’s medical history, it can make an important contribution to the disability determination process. In many cases, an etiological diagnosis can provide a valid basis for determining if economic hardship is associated with the presence of a disability or some other circumstance. The case of prenatal alcohol exposure can serve to illustrate this point. Fetal alcohol syndrome and alcohol-related neurodevelopmental disorders result from maternal consumption of alcohol during pregnancy. These disorders represent one of the leading preventable causes of birth defects, mental retardation, and neurodevelopmental disorders. Fetal alcohol syndrome is estimated to occur in 5.2 per 10,000 live births in the United States (Centers for Disease Control and Prevention, 1997; Cordero et al., 1994). While some individuals may be more vulnerable, perhaps due to their genetic makeup, the immediate cause is clearly a nongenetic factor. Fetal alcohol syndrome results in characteristic facial features, including microcephaly, short palpebral fissures, thin upper lip, flat philtrum and midface, as well as intellectual impairment together with behavioral, emotional, and tone abnormalities. In one study (Streissguth et al., 1996), up to 94 percent of children and young adults with the syndrome had mental health problems, including 61 percent

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Mental Retardation: Determining Eligibility for Social Security Benefits with attention deficit hyperactivity disorder, over 50 percent with depression, and 29 percent with psychotic symptoms. Streissguth et al. also reported a mean IQ for their sample of children and young adults of 79, while adaptive skills were more than two standard deviations below the reference population mean. Prenatal alcohol exposure can produce a spectrum of disorders including: (a) fetal alcohol syndrome, (b) fetal alcohol syndrome without confirmed exposure to alcohol, (c) partial fetal alcohol syndrome with confirmed exposure, (d) alcohol-related birth defects, or (e) alcohol-related neurodevelopmental disorder. The severity of impairment can also vary widely from case to case, with some individuals having severe and easily recognizable signs and symptoms and others having more subtle effects that can be difficult to recognize. In addition, when diagnosis occurs after infancy or early childhood, it can be difficult to document the linkage between symptoms and prenatal alcohol exposure convincingly, especially in individuals with milder impairments. Despite these difficulties, once signs and symptoms are evident and a diagnosis is made, it is likely that fetal alcohol syndrome (or one of the other conditions associated with prenatal alcohol exposure) will be a major contributing factor to substantial difficulties in school achievement, development of social skills, and maintenance of employment. Of course, mental retardation can be evident in many individual cases, but even in borderline situations, the other behavioral and functional impairments associated with prenatal alcohol exposure can safely be assumed to limit opportunities for achieving economic self-sufficiency. In these cases, SSA might consider the etiological diagnosis in arriving at its determination of eligibility for benefits. CONCLUSIONS AND RECOMMENDATIONS In reviewing the literature on the differential diagnosis of mental retardation from other disorders with similar signs and symptoms, the committee concludes that it is necessary to use multiple sources of objective data, including but not limited to, IQ test results, assessments

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Mental Retardation: Determining Eligibility for Social Security Benefits of adaptive behaviors, academic test results, and structured interviews, to determine whether an individual meets diagnostic criteria for mental retardation. Many neurodevelopmental and psychiatric disorders, such as autism, pervasive developmental disorder, attention deficit hyperactivity disorder, cerebral palsy, sensory impairments, and seizure disorders, are associated with mental retardation and complicate its diagnosis. Many of these disorders are currently defined as making the client automatically eligible for SSI benefits. Individuals who have mild mental retardation may be eligible for SSI, on the basis of concurrent neurodevelopmental or psychiatric disorders. The committee also concludes that accurate evaluation of infants and very young children requires special attention to selecting and using appropriate evaluation instruments, conditions of test administration, experience of the evaluator, and concurrent medical and psychosocial risk factors. The committee concludes that learning disability in school-age children can be differentiated from mental retardation by examining data from cognitive, adaptive, and academic testing. Children who have learning disabilities rather than mental retardation have significantly lower academic performance than their peers, but they do not meet criteria for mental retardation—i.e., they have composite IQs over 70 and performance difficulties focused in specific domains of cognitive and academic content. Like learning disability in school-age children, borderline intellectual functioning may be differentiated from mental retardation by reviewing cognitive and adaptive functioning evaluations. Children with composite IQ scores of 71-75 without the adaptive behavior deficits required for a diagnosis of mental retardation can be classified as having borderline intellectual functioning. It is the combination of composite IQs and adaptive behavior deficits as described in Chapter 5 that provides the best operational definition for mental retardation. Research data show that adolescents and young adults with mental retardation are at high risk for developing a range of behavior disorders or psychiatric impairments. In that case, they are more accurately

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Mental Retardation: Determining Eligibility for Social Security Benefits described as having a dual diagnosis. Behavioral or mental health disorders can further complicate the differential diagnosis of mental retardation, frequently depressing scores on tests of cognitive or adaptive functioning. In these cases, reevaluation of the individual is warranted after treatment of the mental health disorder. Research data also make it clear that cultural and socioeconomic background has profound effects on the assessment and the interpretation of behavior, particularly by proxy respondents. The disability examiner must take this into account as he or she prepares the client’s assessment, using other sources of data as needed for an accurate diagnosis. On the basis of the data reviewed in this and previous chapters, the committee makes the following recommendations related to distinguishing mental retardation from other conditions with which it shares signs and symptoms. Recommendation: Social Security Disability Determination Specialists may differentiate other conditions from mental retardation by using intelligence and adaptive behavior test criteria as outlined in the committee’s recommendations. Data, including school test results, intelligence and adaptive behavior test results, and psychiatric and medical test results, from community-based agencies (such as schools, hospitals, or clinics) can be used to inform the determination of SSA eligibility for the diagnosis of mental retardation, but the diagnoses given by community agencies should not be used. Social Security Disability Determination Specialists may differentiate individuals with borderline intellectual functioning and learning disability from those with mental retardation by reviewing cognitive and adaptive behavior test results and determining whether the individual meets diagnostic criteria for mental retardation as recommended in Chapters 3 and 4. Social Security Disability Determination Specialists do not

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Mental Retardation: Determining Eligibility for Social Security Benefits need to determine the presence or absence of mental retardation in individuals who are eligible for SSI due to other neurodevelopmental or psychiatric disabilities (e.g., autism, pervasive developmental disorder, attention deficit hyperactivity disorder, genetic syndromes, intrauterine exposure to alcohol or environmental toxins, sensory impairments, seizure disorders, or severe emotional-behavioral disorders). Objective data on intellectual and adaptive functioning to determine mental retardation should be collected for individuals with mild neurodevelopmental or psychiatric disabilities who might have impairments that are consistent with or functionally equivalent to mental retardation.