Mental Retardation

Introduction

Intellectual disability comprises a heterogeneous group of people, who in their school years are singled out as having general difficulty in learning, and in adult life as having limitations in their independent community functioning. The present entry describes how to assess [Page 580]intelligence and cognitive processes, adaptive skills and social functioning and behavioural problems in persons with intellectual disability. We use intellectual disability in addition to mental retardation because it is currently the broadly accepted scientific definition for identifying the population group diagnosed with adaptive and intellectual limitations. The term ‘mental deficiency’ was widely used during the 1970s and beginning of the 1980s, but by the second half of the 1980s it had been replaced by ‘mental retardation’. Nowadays, the preferred term for professionals and scholars worldwide is ‘intellectual disability’.

Intellectual disability cannot be understood as a characteristic of the individual, despite the fact that it has traditionally been classified as a medical or psychiatric disorder. Since 1992, with the significant paradigm shift in the concept of mental retardation proposed by the American Association on Mental Retardation (AAMR) (Luckasson et al., 1992), it has been considered that mental retardation refers to substantial limitations in present functioning. This means that we are now emphasizing individuals' functioning instead of their characteristics. Individuals' functioning is understood as the result of the adjustment between personal abilities and characteristics, and environmental expectations. Consequently assessment should not focus as much on the individual as on the environment around him.

Present Concept of Intellectual Disabilities

The present conceptual approach to the definition of intellectual disability is not a medical model, although the medical model can describe the aetiology, nor is it a psychometric or psychopathological model, although the former is fundamental for determining competence in intelligence and the latter can describe the thoughts or behaviours experienced by a person with mental retardation. The AAMR proposes a functional model based on the integration of multidisciplinary and multidimensional perspectives addressed at specifying the needs of the individual in order to determine the type and intensity of the supports needed. Mental retardation is not considered an absolute feature of the individual but the expression of the interaction between the person with limited intellectual functioning and the environment. To talk about mental retardation does not mean to talk about people with certain characteristics, but about the restricted functioning of people with specific personal limitations.

We should not suppose that mental retardation is pervasive throughout the lifespan of the individual. In fact, the prevalence of mental retardation in adult life decreases because the requirements of social and cultural environments are not as high as the demands of school regarding educational performance and disciplined group behaviour. The existence of mental retardation is defined by the evaluation of the need to provide supports for the normal functioning of the individual.

Although a multidisciplinary approach is proposed, psychology is the discipline which tends to focus more on the individual and their interaction with the environment, and therefore psychologists should organize and define key decisions in the assessment process (Jacobson & Mulick, 1996). Mental retardation assessment consists of a formal diagnosis and the functional description of strengths and weaknesses of the individual, together with his needs. A competent person will carry out the diagnosis through psychological tests, but in order to have an appropriately developed functional description of the individual it will need to be devised by a multidisciplinary team. The team should be made up of people who spend greater time with the person, both within a family context and through supporting services and programmes.

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