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14. Developmental Disorders.pdf

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York University
PSYC 3230
James Alcock

14. Developmental Disorders Monday, April 1, 20138:54 AM Mental Retardation • Involves a broad delay in cognitive and social functioning • Course is variable ○ Many children improve considerably over time ○ Especially in enriched environments-- encouragement, support, and stimulation • Impoverished environments may lead to deterioration • Training programs to develop community and social skills have been developed • Famous People Players (Toronto)-- mentally and physically challenged actors, highly acclaimed theatre troupe; first theatre company in the world dedicated to people with special needs • Three criteria for diagnosis, according to the DSM-IV: ○ IQ score of 70 or below on a standard IQ test such as WISC or Stanford-Binet ○ Evidence of impaired functioning in two or more areas of adaptive behavior-- e.g., self- care, school, work, social skills ○ Onset before age 18 • Assessed in terms of level of severity: ○ Mild mental retardation: IQ 50-70 (85% of mentally retarded) ○ Moderate mental retardation: IQ 35-49 (10%) ○ Severe mental retardation: IQ 20-34 (3-4%) ○ Profound mental retardation: IQ < 20 (1-2%) • Biological roots ○ Chromosomal and genetic diseases ○ Infectious diseases ○ Brain damage due to environmental toxins ○ Anoxia during birth, etc. • Impoverished home environment can combine with biological factors to produce a more serious disorder Down Syndrome • One of the most common causes of mental retardation • Down symptoms, along with retardation, include: ○ Flat face, small nose, eyes that appear to slant forward because of small folds of skin at inside corners ("mongoloids") small ears, small short hands with curved fifth finger ○ Likely to be obese in childhood and adolescence ○ Tend to have congenital heart abnormalities ○ Tend to show a form of senility • Due to chromosomal abnormalities ○ Each parent contributes one of each of 23 pairs of chromosomes in the zygote ○ Down syndrome occurs when there are three instead of two chromosomes at position 21 Can occur in two ways; [95% is related to the mother's egg] ○ Can occur in two ways; [95% is related to the mother's egg] 1) Nondisjunction: one pair of chromosomes in formation of egg or sperm did not separate-- accounts for 80 to 90% of cases (also referred to as "trisomy") □ Risk of nondisjunction rises dramatically in women over 40 (<1 per thousand for women in 20s; 18 per 1000 for women over 40) 2) Translocation: Sometimes material from a chromosome at 21 breaks off in the formation of an egg and fuses with another, so that during cell division, it is carried to the zygote • Karyotype: photograph of all the chromosomes in a cell Phenylketonuria(PKU) • Inherited metabolic disorder caused by a recessive gene carried by one person in 60 ○ Occurs in 1 out of every 12,000 births in North America ○ Prevents child from metabolizing the amino acid phenylalanine, found in many foods  Leads to brain damage and retardation • Left untreated during infancy, leads to severe, irreversible mental retardation • May also experience neurobehavioral symptoms-- seizures, tumors, etc. Fragile X Syndrome • A common cause of inherited mental retardation ○ Related to genes on X chromosome (from mother) ○ "Fragile" spot on chromosome shows up when the chromosome is cultured in a laboratory • Fragile X syndrome is a spectrum of mental impairment-- from learning disabilities to severe retardation • Expression is variable • Moderate to severe mental retardation is most common symptom • Macroorchidism (large testicles) • Karyotypes of individuals with Fragile X syndrome are missing a small piece of X chromosome near the end Fetal AlcoholSyndrome • Due to alcohol intake during pregnancy ○ Causes mental retardation and various physical disorders-- e.g., flattened nose, widely separated eyes, reduced head size, below average height and weight Tay-SachsDisease • Caused by recessive gene found mostly in Jewish people of eastern European origin (1 in 25 Jews in North America is a carrier) • Usually causes death before age 5 OthersCauses of Retardation • Despite these biological roots, about 75% of people diagnosed as having a developmental handicap have no known organic cause or brain dysfunction! • Most of these are in the mild range Not clear what the cause is-- "inherited low intelligence" combined with an ○ Not clear what the cause is-- "inherited low intelligence" combined with an impoverished environment? Autism • If one looks at textbooks from thirty years ago, autism was considered to be "…a subgroup of psychotic disorders" • In DSM-IV, autism is considered to be a pervasive developmental disorder • Symptoms are usually present within the first year and a half of a child's life. In some children, the symptoms may show up early on, within the baby's first few months of life • Other babies may appear normal for a while and then suddenly exhibit an alarming regression at 18 to 24 mon
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