Prevention of Intellectual and Developmental Disabilities

Abstract

The first plenary session of 132nd Annual Meeting of the American Association on Intellectual and Developmental Disabilities (AAIDD) reflected its support for basic and applied research to prevent or minimize the effects of conditions causing developmental disabilities, with Dr. Alan Guttmacher (2008), currently the acting director of the National Human Genome Research Institute, discussing the realized and potential benefits of genomics research on health and quality of life. This presentation dealt with an incredibly complex topic with clarity and sensitivity, and it was carefully neutral in tone and content with respect to intellectual and developmental disabilities. Nevertheless, a major implication regarding disabilities in general and developmental disabilities more specifically was quite clear. Current research in genomics, as well as in many other areas, is intended to improve understanding of the fundamental causes of disability to reduce risk, thereby lowering incidence of impairments and minimizing their severity. Should these goals be realized, the proportion of the population with disability would decrease, perhaps dramatically, and in some distant future significant impairments might even be eliminated altogether. As unachievable as that ultimate goal might appear to be, an assumption supporting many of the programs and much of the research agenda in the field of developmental disabilities is that we, as a society and as individuals, would be better off if physical, mental, and cognitive impairments ceased to exist.Yet, prevention encompasses many things and can be viewed from many perspectives, some of which have continued to challenge the universality of this assumption. There is a need for serious and open discussion of the many aspects of prevention within our field (and the disabilities field more generally) that entails explicit consideration of risks and benefits of specific programs and approaches to implementation. Although important distinctions can and should be made among primary prevention (avoiding the occurrence of a causal condition), secondary prevention (avoiding or minimizing the consequences of a causal condition after it occurs), and tertiary prevention (minimizing or improving outcomes after the consequences of a causal condition are evident), this dialogue needs to begin with consideration of the overarching goal of lowering the incidence and prevalence of impairments and reducing disability.In many respects, prevention was embraced long ago as a valued societal benefit, and this has had significant impacts in the case of intellectual and developmental disabilities. Certainly, the history of prevention in our own field has included some policies and actions that had devastating consequences for people with intellectual and developmental disabilities, and careful and constant vigilance will always be required to ensure that the rights, privileges, and dignity of every individual are respected and preserved. Nevertheless, many other aspects of the past continue to be broadly viewed as enormously beneficial, and several examples seem particularly illustrative.Until the late 19th century, congenital hypothyroidism (cretinism) caused many individuals in western Europe to have intellectual disability. For some alpine regions, it was so common an occurrence that local physicians thought it unremarkable (Merke, 1984). We now know that this condition is caused by dietary iodine deficiency, and this discovery, along with the availability of iodized salt, has virtually eliminated it as a public health concern in industrialized countries. (Nevertheless, congenital hypothyroidism remains one of the most common preventable causes of intellectual impairment in many underdeveloped regions of the world; Jain, Agarwal, Deorari, & Paul, 2008.)Prior to the 1950s, babies born with phenylketonuria (PKU), a relatively rare genetic disorder, were unimpaired at birth but invariably developed severe intellectual disabilities. This was caused by their inability to metabolize phenylalanine, a nutrient present in many everyday foods (including breast milk). Over time, the build up of abnormally high levels of phenylalanine has neurotoxic effects (Jervis, 1939), and, thanks to this discovery, a highly specialized diet was developed that has been successfully preventing disability in affected babies ever since. (All newborns in the United States are currently screened for PKU plus a growing number of other conditions, providing the basis for early diagnosis and prevention.)In the 1960s, a vaccine was developed with the intention of eradicating rubella (German measles), largely because infants exposed in utero were at high risk for intellectual and developmental disabilities. This vaccine has reduced the incidence of congenital rubella syndrome from 20,000 cases during the epidemic of the 1960s to less than 25 annually in the United States (U.S. Centers for Disease Control and Prevention, 2005). Current programs to reduce alcohol consumption by pregnant women are strongly endorsed and broadly supported for much the same reason, in this case to prevent fetal alcohol syndrome and related disorders, as is the use of folate supplements during pregnancy to reduce the incidence of neural tube defects (Pitkin, 2007). Obstetric practices have improved to avoid brain injury due to perinatal hypoxia and mechanical injury, as well as transmission of maternal viral infections that might affect babies' development. Environmental exposure to lead and mercury is being reduced to avoid their potentially neurotoxic effects, and the list could go on.Although these examples might suggest that there is no down side to prevention, the lessons of history show otherwise. Eugenics movements have gained momentum periodically, and there will always be some people in favor of imposing their views on those they see as less worthy than themselves. We are fortunate that we live in relatively enlightened times, but no matter how enthusiastic supporters of prevention may be, they must always be mindful of potential abuses. Furthermore, it must be emphasized that one of the most pressing issues facing our field has been conspicuously avoided in these examples: elective pregnancy termination based on the results of prenatal screening and diagnosis. Consideration of this critically important subject, along with the negative biases of many clinicians toward developmental disability (see Bauer, 2008), must be a major part of any dialogue about prevention. Even leaving this issue of life and death aside, though, an outspoken segment of our community vehemently opposes prevention. As expressed by the final comment from the audience at Guttmacher's (2008) plenary presentation identifying “the elephant in the room,” some among us would “not want to live” in a world without intellectual and developmental disabilities. The commitment of this gentleman and his like-minded colleagues is beyond question, as is their regard for individuals with disabilities. However, other people share this commitment yet endorse the concept of prevention (although not necessarily all the strategies for possible implementation). The real elephant in the room, then, seems to be the question of whether a high regard for individuals with developmental disability inherently conflicts with support for prevention of the impairments affecting those very same people. There are certainly many ways to explore the answer to this question, but all of them should consider the logical connection between the two values in apparent opposition.Capturing the essential spirit of why people with intellectual and developmental disabilities should be valued as highly as people without disability, begin by accepting that (a) every person should have the same basic human rights and be recognized as an autonomous and unique individual and (b) each of us is capable of contributing in important ways to the diversity that enriches the human experience. In addition, accept that for every individual, each with his or her own unique profile of strengths and weaknesses, maturation and development depend critically on growth and change throughout the lifespan. Achievement of individualized successful development involves complex interactions among nature and nurture (and good fortune, no doubt), but specifics are unimportant for this discussion. It is only important to recognize that change is a natural part of life that incorporates growth, learning, and maturation and that individual characteristics must be viewed as dynamic rather than static.Once this is accepted, impairments, when present, should be recognized as just one type of personal characteristic among many, and, having no special status, impairments should also be viewed as dynamic and changeable. All treatments are based explicitly or implicitly on this premise, which is the driving force behind a host of programs that include access to a full and appropriate public education for all children (e.g., Public Law 94–142) and virtually all habilitation, education, and training. Shifting back to prevention, if impairments are subject to change, including reduction in severity, the logical foundation for opposing avoidance of their occurrence in the first place seems to collapse.As Guttmacher (2008) emphasized by the title of his plenary talk, “We Are All Mutants…,” each of us is imperfect and vulnerable in one way or another. Any one of us can cross that threshold of impairment at any time, and in promoting acceptance of diversity and the value of people with disabilities, advocates serve all members of our society. Particularly at this juncture, when amazing advances in biomedical sciences and engineering are having dramatic impacts on practice and policy, it seems more important than ever to engage in an explicit evaluation of prevention and treatment from the diverse perspectives that make up the field of intellectual and developmental disabilities. A consensus is needed before the risks and benefits of specific policies, positions, and actions can be evaluated, and although that consensus might already exist outside of a small but vocal antiprevention minority, it seems at least as likely that core beliefs about prevention and treatment vary substantially. The stakes are enormous, and it would be incredibly useful to know the reality of current thinking.We each need to determine where we stand as part of the process of either building that consensus or determining that it can not be reached, and the process could start with each of us posing fundamental questions to ourselves and to others, such as: If impairments do not devalue individuals, why would successful treatment of those very same impairments? Does it follow that if successful treatment would not devalue these individuals, then prevention of impairments in others would not? Would we treasure our children with intellectual and developmental disabilities as much without their cognitive impairments? If we ever discover how to cure intellectual disability, should treatment be universally available? Has virtual eradication of congenital hypothyroidism in industrialized countries been beneficial, or have we tragically lost an entire class of people? Perhaps the most fundamental question of all is: What would we really think of a world where people without sight could see, where people unable to stand could run, and where people with intellectual disability were without their “significant limitations both in intellectual function and adaptive behavior” (American Association on Mental Retardation, 2002, p. 1)?Support was provided by Grant P30 HD024061 (M. Cataldo, Principal Investigator) from the Intellectual and Developmental Disabilities Branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development. I thank Drs. Michael Guralnick, Steven F. Warren, and Warren Zigman for many thoughtful comments on an earlier draft of this article.