630 CHAPTER 14
and body rocking (American Psychiatric Asso-
ciation, 2000); and (2) self-injurious behaviors,
such as hitting the head against something and
hitting or biting oneself. People with mental re-
tardation who exhibit both stereotypic behav-
iors and self-injurious behaviors have greater
deficits in nonverbal social skills than those
with only one type of problematic behavior
(Matson et al., 2006). Other problematic be-
haviors that often go along with mental retar-
dation include consistently choosing to interact
with objects rather than people, inappropri-
ately touching others, and resisting physical
contact or affection. How or why all these be-
haviors arise is not yet known.Social Factors: Understimulation
Another way in which mental retardation can arise is when an infant’s environment
is severely understimulating or the infant is undernourished (Dennis, 1973; Dong &
Greenough, 2004; Skeels & Dye, 1939). However, in 30–40% of cases, there is no
clear cause for the mental retardation; when there are clear etiological factors, the
diagnosis is generally in the severe or profound range.In sum, most cases of mental retardation arise primarily from neurological
factors—genes or teratogens, which in turn lead to abnormal brain structure and
function, leading to cognitive defi cits. Moreover, children with mental retardation
may exhibit stereotyped or self-injurious behaviors.Treating Mental Retardation
Mental retardation cannot be “cured,” but interventions can help people to func-
tion more independently in daily life. Such interventions are designed to improve the
person’s ability to communicate and other skills. But more than that, clinicians
try to prevent mental retardation from arising in the fi rst place. Prevention efforts
seek to avert or reduce the factors that cause mental retardation.Targeting Neurological Factors: Prevention
Because the key causes of mental retardation are neurological, this type of factor
is the target of prevention efforts. Two successful prevention efforts focus on phe-
nylketonuria (PKU) and exposure to lead. Since the 1950s, virtually all newborns
in the United States receive a test to detect whether they have PKU, which consists
of a problem metabolizing the enzyme phenylalanine hydroxylase. For newborns
testing positive, lifelong dietary modifi cations can prevent any brain damage, thus
preventing mental retardation. Another successful prevention effort involves child-
hood exposure to lead, which can lead to brain abnormalities. As noted earlier, lead
was banned as an ingredient in paint in 1978; laws were passed that required land-
lords and homeowners to inform any prospective renters or buyers of any known
lead paint on the property. Beginning in the 1970s, lead was also phased out as an
additive to gasoline. As a result of these measures, lead exposure—and lead-induced
mental retardation—has decreased.
There are no neurological treatments for mental retardation, although symp-
toms of comorbid disorders may respond to medication.Targeting Psychological and Social Factors: Communication
Given the defi cits and heterogeneous symptoms that accompany mental retardation,
no single symptom is the focus of all psychological and social treatments. Rather,
psychological and social treatments depend on the individual’s specifi c constellationWhen this child gets excited, she engages
in the stereotyped behavior of hand-
fl apping. Other stereotyped behaviors
exhibited by people with mental retarda-
tion include rocking back and forth and
repeatedly moving a fi nger.Maria Platt-Evans/Photo ResearchersP SN