The evolution of the concept of intellectual disability

After the discovery and establishment of psychometric and factorial methodology in the study of intelligence at the beginning of the last century by Alfred Binet and Simon (1905) and later, Terman (1916) and Weschler in the 1930s, the intellectual coefficient has become the central factor in the assessment of intellectual ability.

however, the latest proposal from the American Association on Mental Retardation (AAMR) from 1992 seems to spare some of the drawbacks associated with the first formula.

    Intellectual disability as a neurodevelopmental disorder

    Neurodevelopmental disorder (or neurodevelopmental disorders, according to the DSM-V) is understood as any disease related to an alteration during the maturation process of the nervous system resulting in inadequate functioning in behavior, thinking, movement, learning, perceptual-sensory ability and other complex mental functions.

    The set of manifestations that can occur as a result is of a very wide variety, because it must take into account both the location of the dysfunction, the influencing environmental factors as well as the developmental time in which this alteration occurs.

    Neuroscience is the discipline responsible for the study and research of TND, as well as other neurodegenerative disorders, static lesion disorders, and psychiatric disorders. In some cases, the same pathology can be considered in several of these categories, Which differ from each other around two dimensions: time (development-decline) and phenomenological (cognitive-emotional).

    his characteristics

    Among the characteristics attributed to TND, it is difficult to distinguish whether the origin of the external manifestation of the underlying symptomatology is derived from TND or from a normative type of functioning, such as the case of distractibility (which can be due to an alteration of the structures that regulate the attention span or can be a marked personality trait, simply).

    like that, no biological markers are known (Neuroimaging tests or analyzes) from which it can unequivocally diagnose TND-1. The subjectivity of the assessor therefore plays an important role in the diagnosis of the case.

    Secondly, TNDs have a very strong comorbidity with other pathologiesA fact that in some occasions can make an exact diagnosis of the case difficult because all the labels present must be detected. On the other hand, the delineation between symptoms attributable to one disorder and another is also complex, as many of them share common criteria (for example, the difficulty of social relations in a case of autism and language ).

      Types of neurodevelopmental disorders

      Generically, TNDs can be classified into three main categories according to the criteria:

      Whether or not a specific cause is identified

      In this case, genetic influence is an important causal factor. The most widely used classification manuals (DSM and CIE) include communication, learning, hyperactivity and autism spectrum disorders. In the case of conduct disorders, schizophrenic disorders and Gilles de la Tourette’s disorder, the age difference of onset for each of them must be taken into account, so that depending on the case they can also be included. in this first category.

      Genetic alterations linked to structural alteration

      Easier delimitation, since the phenotypic differences are clearly identifiable (deletion, duplication, translocation, chromosomal disomies or trisomies, etc.), as in the case of Williams syndrome.

      TND linked to known environmental cause

      Its influence in interaction with genetic factors is generally taken into account, for example fetal poisoning by maternal alcohol consumption or pathologies derived from the action of valproic acid.

      The traditional conceptualization of intellectual disability

      As indicated at the beginning of these lines, the last century has been marked by the rise of psychometric scales on the evaluation and quantification of the level of intelligence of the human being.

      Thus, it was considered as the only reference determining the distinction between levels of classification of intellectual disability depending on the individual’s IQ. Let’s see a more detailed description of each of these categories:

      Mild mental retardation

      Includes a CI between 55 and 70 and presents a proportion of 85% of the total cases. Being the least significant level of severity, it is difficult to distinguish it in the first years of life. In this case, social and communicative skills or the capacity for autonomy are better preserved, even if they require some kind of supervision and follow-up. There are no great difficulties in achieving the development of a satisfying life.

      Moderate mental retardation

      A second higher severity level with a prevalence of 10% is that of moderate mental retardation, which is assigned an IC between 40 and 55. In this case the level of social and communicative development is lower and need to be cared for in the professional and personal lives of adults, although they continue to adjust to community life in most cases.

      Severe mental retardation

      Severe mental retardation is associated with an IC between 25 and 40 and occurs in 3 to 4% of all cases. Their linguistic capacity is however very limited they are able to develop basic personal care habits. They need a considerable level of support and help to adjust to community life.

      Profound mental retardation

      Profound mental retardation is characterized by an IC less than 25 and is present in 1 to 2% of the population with MRI. At this level, they are observed clear and severe motor, sensory and cognitive difficulties. They require constant and permanent monitoring and a strong structuring of the environment in which they interact.

        Descriptive dimensions of intellectual functioning

        The latest proposal from the American Association on Mental Retardation (AAMR) involves a radical change in the conception of intellectual disability and emphasizes the endowment of the definition of mental retardation. a little more positive and optimistic connotation in terms of primarily assessing the capacities and potentials of the individual with intellectual dysfunction, as well as the supports they need to achieve these goals.

        Thus, the AAMR’s proposed definition of mental retardation explains it as a series of substantial limitations in intellectual functioning, which is significantly below average and manifests before age 18.

        Dimensions of the mental retardation assessment

        More specifically, the major dimensions proposed by the AAMR on those of the functional level assessment of the skills available to the child and what it can achieve with a multidisciplinary global intervention:

        • Intellectual skills.
        • Conceptual, social and practical adaptive behavior.
        • Participation, interactions and social roles.
        • Physical and mental health, etiology of possible alterations.
        • Social context, linked to the environment, culture and opportunities for access to this type of stimulation.

        Unlike the previous ones, this proposal emphasizes the social context and determines the resources necessary to ensure the greatest amount of learning, autonomy and well-being of the child on a daily basis, instead of taking as a factor central deficits and difficulties. that the little one presents.

        This has several advantages both in terms of reducing the negative labeling that is generally associated with individuals with this type of deficiency, as the definition gives a major role to the potential and capacities to be developed by the child. In addition, this new definition sand is more oriented to determine the type of intervention which will be necessary for the specific case to obtain the highest possible level of development (environmental, social, personal and intellectual adaptations).

        In this new conception, the following assumptions are presupposed: taking into account cultural and linguistic, communicative and behavioral diversity; the need for the existence of individualized supports at the community level; the coexistence of potentialities in other adaptive domains or personal capacities; the hypothesis of improving the person’s functioning by providing him with appropriate supports over a continuous period.

        In short, this seems to be the most recent definition of mental retardation. it aims to provide a more practical, positive and adaptive perspective which will facilitate a greater integration of the individual both personally and socially, allowing further development by emphasizing his qualities rather than his difficulties.

        Bibliographical references:

        • Artigas-Pallarés, J. and Narbonne, J. (2011): Neurodevelopmental disorders. Barcelona: Viguera editors.
        • American Psychiatric Association (APA, 2013). DSM-V. (American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders. Washington, DC).
        • Botxí A. (1994) The paradigm shift in the conception of mental retardation: the new definition of AAMR. Zero century.

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