The signs of mental retardation are generally recognized and assessed during childhood. In order to be officially diagnosed with mental retardation (MR), an individual must have an intelligence quotient (IQ) below 70, must exhibit behavioral signs of mental retardation and must exhibit these signs before the age of 18. Generally speaking, a child shows signs of mental retardation when he or she is consistently behind his or her peers when assessed using common developmental milestones.
There are several keys signs of mental retardation. Mental retardation is a generalized disorder, so the most obvious signs are behavioral in nature. Key signs in adults include demonstrated deficits in logical thinking, inability to generalize and difficulty with abstract thinking. Mentally handicapped children and adults are more likely to view the world in concrete, literal terms. Allusion, social subtleties and outcome prediction present a challenge.
Adaptive behaviors, behaviors used to compensate for or mask difficulties performing everyday tasks, can often occlude the initial signs of mental retardation, especially in young children who are mildly affected. Therapists advise parents, teachers and other caregivers to seek the advice of a specialist before assuming that a child suffers from a mental disability. Some behavior problems, or even boredom with standard school subjects, can be misinterpreted as a mental disability.
Specialists in mental retardation generally recognize three categories, or levels, of mental disability. These are mild mental retardation, moderate mental retardation and profound mental retardation. Each is accompanied by different signs of impairment.
Mild mental retardation is defined as having an IQ of 50-69. About 85 percent of the mentally retarded population is mildly mentally retarded. Language skills are somewhat delayed, as is the acquisition of self-care skills such as dressing and eating. Memory is also somewhat impaired.
Individuals who have mild mental retardation might go through their early developmental years without being diagnosed, but more severely affected children exhibit pronounced developmental delays much earlier. Moderate mental retardation, defined as an IQ of 35-49, generally becomes apparent before the child's second birthday. Significant speech and social skills are significantly delayed.
Profoundly impaired individuals have an IQ of 20-34. Language and motor skills generally are severely limited or not present. Full-time care is generally required through adulthood.