The Evolution of the Concept of Intellectual Disability

The way of evaluating and assessing the nature of Mental Retardation has changed a lot over the years.

Following 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, IQ became the central factor in the assessment of intellectual ability.

However, the more recent proposal of the American Association on Mental Retardation (AAMR) of 1992 seems to overcome 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 a disturbance during the maturation process of the nervous system which results in inadequate functioning at the level of behavior, thinking, movement, learning, perceptual-sensory capacity and other complex mental functions.

The set of manifestations that can occur as a consequence are of a very considerable variety, since the location of the dysfunction, the influential environmental factors and also the time of development in which the alteration occurs must be taken into account.

Neuroscience is the discipline in charge of the study and investigation of NDD, as well as other neurodegenerative disorders, static lesional disorders and psychiatric disorders. In certain cases, the same pathology can be considered within more than one of these categories.which differ from each other along two dimensions: time (developmental-decline) and phenomenological (cognitive-emocinal).

Their characteristics

Among the characteristics attributed to NDD, it is difficult to distinguish whether the origin of the external manifestation of the underlying symptomatology is derived from NDD or from a type of normative functioning, as for example in the case of distractibility (which may be due to an affectation of the structures that regulate attentional capacity or may simply be a marked personality trait).

Thus, there are no known Biological markers (neuroimaging tests or analyses) on the basis of which an NDD can be unequivocally diagnosed. The subjectivity of the evaluator therefore plays a significant role in the diagnosis made of the case.

Secondly, TND present a very high comorbidity with other pathologies, a fact that in certain occasions can make difficult an exact diagnosis of the case.This fact can sometimes make it difficult to make an accurate diagnosis of the case, since all the labels present must be detected. On the other hand, the delimitation between the symptomatology attributable to one disorder and another is also complex, since many of them share common criteria (for example, the difficulty in social relations in a case of autism and language disorder).

Types of Neurodevelopmental Disorders

Generically, NDD 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 a significant causative factor.. The most widely used classification manuals (DSM and ICD) include communication disorders, learning disorders, hyperactivity disorders and autism spectrum disorders. In the case of conduct disorders, schizophrenic disorders and Tourette's disorder, the difference in age of onset for each of them must be taken into account, so depending on the case, they can also be included in this first category.

Genetic alterations linked to a structural alteration

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

TND linked to a known environmental cause

Usually their influence is considered in interaction with genetic factors, for example fetal intoxication 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 was marked by the rise of psychometric scales on the assessment and quantification of the level of intelligence in human beings.

Thus, the only determinant referent was the distinction between the distinction between the classificatory levels of Intellectual Disability according to IQ according to the Intellectual Coefficient (IQ) of the individual. Let us see a more detailed description of each of these categories:

Mild Mental Retardation

Comprises an IQ between 55 and 70 and presents a proportion of 85% of all cases. Being the least significant level in severity, it is difficult to distinguish in the first years of life. In this case, social and communicative skills or the capacity for atonomy are rather preserved, although they require some supervision and follow-up. There are no major difficulties in achieving the development of a satisfactory life.

Moderate Mental Retardation

A second level of greater severity with a prevalence of 10% is that of Moderate Mental Retardation, to which an IQ between 40 and 55 is attributed. In this case the level of social and communicative development is lower, and they must be and they must be tutored during working and personal adult life, although they are still able to adapt to community life in most cases.

Severe Mental Retardation

Severe Mental Retardation is associated with an IQ between 25 and 40 and occurs in 3-4% of all cases. Their linguistic ability is very limited but they are they are capable of acquiring elementary self-care habits.. They need a considerable level of supports and assistance to adapt to community life.

Profound Mental Retardation

Profound Mental Retardation is characterized by an IQ lower than 25 and is present in 1 to 2% of the population with MR. At this level, there are severe motor, sensory and cognitive difficulties are observed at this level.. They require constant and permanent supervision and a high structuring of the environment in which they interact.

The descriptive dimensions of intellectual functioning

The most recent proposal of the American Association on Mental Retardation (AAMR) implies a drastic change in the conception of intellectual disability and puts the emphasis on giving the definition of Mental Retardation a somewhat more positive and optimistic connotation. in terms of assessing mainly the capabilities and potential of the individual with intellectual dysfunction, as well as the supports he/she needs to achieve these goals.

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

Assessment dimensions of Mental Retardation

Specifically, the major dimensions proposed by the AAMR on which to assess at the functional level the abilities available to the child and which can be reached with a global multidisciplinary intervention:

• Intellectual abilities.
• Adaptive behavior at a conceptual, social and practical level.
• Participation, interactions and social roles.
• Physical and mental health, etiology of possible alterations.
• Social context, related to the environment, culture and opportunities for access to this type of stimulation.

Unlike the previous ones, this proposal places emphasis on the social context and on determining what resources are required to guarantee the greatest amount of learning, autonomy and well-being of the child in his or her daily life, instead of taking as a central factor the deficits and difficulties presented by the child.

This has several advantages, both in terms of reducing the negative labeling that is usually associated with individuals with these types of deficits, since the definition gives a major role to the potential and capabilities to be developed by the child. In addition, this new definition s****e is more oriented towards determining the type of intervention that will be necessary for the specific case in order to obtain the highest possible level of development (environmental, social, personal and intellectual adaptations).

This new conception presupposes the following postulates: the consideration of cultural and linguistic, communicative and behavioral diversity; the need for the existence of individualized supports at the community level; the co-existence of potentialities in other adaptive areas or personal capacities; the assumption of the improvement of the person's functioning by providing him/her with the appropriate supports during a continuous period of time.

In short, it seems that the most recent definition of Mental Retardation is intended to provide a more practical, positive and adaptive perspective. which will facilitate greater integration of the individual at both the personal and social level, enabling greater development by emphasizing his or her qualities rather than his or her difficulties.