Included in the DSM-IV-TR Axis II categories are personality disorders and mental retardation. Mental retardation is not considered a cognitive disorder or a personality disorder. There are four different levels of mental retardation specified in the DSM-IV-TR: mild, moderate, severe, and profound. Each level is determined by the range of which the individual scores on the Wechsler scale, which is used to measure an individuals IQ. When one receives a score of 70 or less, displays deficiencies in adaptive behaviors, and have an onset of symptoms before age eighteen, they are considered to be mentally retarded.
Mental retardation is generally diagnosed in infancy, childhood, or adolescence. Two factors seem to contribute to mental retardation, biology and environment. From a biological model, one would assume that genetics contributed to Arnie’s disease. Researchers in this group would look at family history or a genetic abnormality, this could be the absence of or an additional gene on a chromosome, to explain Arnie’s disease. In Arnie’s case, everyone in his immediate family appears to have normal functioning in their daily lives, and there are no apparent physical or mental delays.
We can also look to explain Arnie’s condition from an environmental perspective. From an environmental perspective, there are several factors that may contribute to mental retardation, among