Mental retardation (MR) is a generalized disorder, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors with onset before the age of 18. It has historically been defined as an Intelligence Quotient score under 70. Once focused almost entirely on cognition, the definition now includes both a component relating to mental functioning and one relating to individuals’ functional skills in their environment.
Signs and symptoms
Children with mental retardation may learn to sit up, to crawl, or to walk later than other children, or they may learn to talk later. Both adults and children with mental retardation may also exhibit the following characteristics:
Delays in oral language development
Deficits in memory skills
Difficulty learning social rules
Difficulty with problem solving skills
Delays in the development of adaptive behaviors such as self-help or self-care skills
Lack of social inhibitors
The limitations of cognitive functioning will cause a child with mental retardation to learn and develop more slowly than a typical child. Children may take longer to learn language, develop social skills, and take care of their personal needs such as dressing or eating. Learning will take them longer, require more repetition, and skills may need to be adapted to their learning level. Nevertheless, virtually every child is able to learn, develop and become participating members of the community.
In early childhood mild mental retardation (IQ 50–69) may not be obvious, and may not be identified until children begin school. Even when poor academic performance is recognized, it may take expert assessment to distinguish mild mental retardation from learning disability or emotional/behavioral disorders. As individuals with mild mental retardation reach adulthood, many learn to live independently and maintain gainful employment.
Moderate mental retardation (IQ 35-49) is nearly always apparent within the first years of life. Children with moderate mental retardation will require considerable supports in school, at home, and in the community in order to participate fully. As adults they may live with their parents, in a supportive group home, or even semi-independently with significant supportive services to help them, for example, manage their finances.
A person with a more severe mental retardation will need more intensive support and supervision his or her entire life.