REPORT ABNORMAL PSYCHOLOGY

disability. The physical disability existed may prevent them to undergo screening tests
for the assessment of intellectual functioning. In short, this category will show the
symptoms of intellectual disability but there is insufficient information for the
clinician to undergo systematic tests to detect the kind of intellectual disability. The
exceptional circumstances existed for the diagnosis of the unspecified intellectual
disability. This is the reason needed for the individuals to have reassessment after a
period of time.
1.4 Causes
Apart from that, there are a few causes that allow the development for
intellectual disability (intellectual development disorder) to happen. The genetic
abnormalities and the environmental hazards are two of the main causes of intellectual
developmental disorder.
Firstly, one of the causes of intellectual disability is the genetic abnormalities
that existed. There are a few genetic abnormalities that relate to intellectual disability
such as down syndrome, phenylketonuria (PKU) and fragile x syndrome (FXS). Down
syndrome happens because the individual has an extra copy of chromosome 21 or
normally known as the Trisomy 21 or equivalent to a total 47 chromosomes rather
than a total of 46 chromosomes in a normal individual. The extra chromosome will
cause interference to both brain and body’s development which lead to the disability in
intellectual functioning. Next, phenylketonuria (PKU) which is another genetic
abnormality that causes the missing of an enzyme, phenylalanine hydroxase. Without
phenylalanine hydroxase, the phenylalanine cannot be broken down and then it will
build up and accumulate in the body in which it causes development delay in the
central nervous system (Whitbourne, 2017). Next, fragile x syndrome (FXS) is another
genetic abnormality of intellectual disability. FXS is more commonly occur to male as
they have the sex chromosomes of XY rather than both XX sex chromosomes in
female. So, the only sex chromosome X of male is easier to get targeting as no extra X
sex chromosome is given for male that are able to reduce the genetic defect. FXS
causes changes in fragile X mental retardation 1 (FMR1) gene targets on the X
chromosome in which the FMR1 gene will produce fragile mental retardation protein
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