Causes of Mental Retardation

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Causes of Mental Retardation

• Genetic, environmental, and psychosocial causes

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Key vocabulary

• Perinatal causes
• Perinatal causes
• Postnatal causes
• Social correlates
• Psychological correlates
• Preventative measures

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Key vocabulary

• Roles of genes and chromosomes in heredity
• Autosomal genetic disorders
• Sex linked genetic disorders
• Disorders related to the number of chromosomes
• Disorders with multiple or unknown causes
• Genetic testing and genetic counseling

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Causes

• Direct cause is more frequently not known than
  known
• Many persons with a label of mental retardation
  are considered to have had the potential of
  developing in a typical sequence or rate
• Implication of preventable
• No estimate of numbers

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Prenatal causes

• Teratogens agents causing a defect in a
  developing embryo or fetus
• Infections
• Radiation
• Maternal nutrition
• Low birth weight
• Chromosomal disorders
• Developmental disorders of brain formation
• Environmental influences

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Infections

• Toxoplasmosis
• Rubella
• Cytomegalovirus
• Syphilis
• HIV
• UTI

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Radiation

• Noted with survivors of the A-bomb on Hiroshima
  and Nagasaki
• Radiation has effects depending on the time of
  exposure and intensity (dose)

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Maternal Nutrition

• Malnutrition may have effects both pre- and
  post-natally
• Major concern in developing countries
• Low weight gain in pregnancy has differential
  effects for different populations
• Low birth weightmay result in as much as 40 to
  60 reduction in brain cells

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Maternal age

• Over 36 and under 16 at risk for low birth weight
• Younger mothers prone to giving birth early (LBW)
• Reasons for mental retardation from younger
  mothers or LBW not known

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Lack of Pre-natal Care

• Sometimes racial differential
• Increased risk of premature rupture of amniotic
  membranes
• Maternal health problems
• Drug abuse and other substance abuse
• LBW
• FAS
• FAE
• Nicotine
• Other drugs

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Maternal health problems

• Endocrine disorders e.g., diabetes
• Cardiovascular disorders
• Anemia
• Treatments for disorders affects fetus

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Drug and alcohol abuse

• Drug use increasing
• Alcohol use during pregnancy
• LBW
• Microcephaly
• Heart defects
• Facial abnormalities
• Poor growth developmental delay
• Behavioral difficulties
• Attention problems

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• Nicotine use
• Increased probability of miscarriage
• Developmental delay
• Cocaine, heroine, methadone
• LBW
• Withdrawal
• Small head circumference
• Developmental delay
• Language problems

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Perinatal causes

• Anoxia and asphyxia
• Prematurity- prior to 37 weeks
• Low birth weight under 5 ½ pounds
• Hemorrhages
• Metabolic problems
• Seizures
• Birthing problems
• Multiple births
• Abnormal presentation
• prolaspe of umbilical cord

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• Respiratory distress syndrome
• lack of sulfactant (coats the alveoli)
• Can result in collapsed alveoli
• Jaundice
• Rh incompatibility

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Postnatal causes

• Quality of attachment
• Illnesses
• Encephalitis
• Meningitis
• Poisoning
• Malnutrition
• Injuries

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Psychosocial factors

• Social correlates
• Low SES
• Nutrition
• Poverty
• Family size
• Low maternal intelligence
• Low maternal educational level
• Absence of parents
• Language environment

• Psychological correlates
• Child rearing practices
• Abuse and neglect

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1927- Buck v Bell

• We have seen more than once that the public
  welfare may call upon the best citizens

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• Young child with Down Syndrome

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• Karyotype of typically developing female

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• Turners syndrome
• Affects females
• Incomplete x chromosome
• Short stature
• Webbed neck
• Low hairline in back
• Skeletal deformities

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Fragile X Syndrome

•  Mental retardation Hyperactivity Short
  attention span Tactilely defensive Hand-flappin
  g Hand-biting Poor eye contact Perseverative
  speech Hyperextensible MP joints Large or
  prominent ears Large testicles Simian crease
  or Sydney line Family history of mental
  retardation

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• Fragile X Syndrome
• In males, generally see a decrease in IQs over
  time
• Concrete thinking
• Facial features
• Long face
• High arched palate
• Long ears
• In females, less like to have a label of
  retardation less severe features

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• Fragile X syndrome
• Boys
• distractible and impulsive, with symptoms of
  attention deficit hyperactivity disorder (ADHD)
• short attention spans and difficulty staying on
  task. 
• stereotypic behaviors, such as hand flapping and
  chewing on skin, clothing, or objects,
• Sensory processing problems may manifest
  themselves as tactile defensiveness, or sensory
  defensiveness.
• Anxiety in both boys and girls manifests itself
  in various ways
• Girls may show less hyperactivity, but still have
  many symptoms of ADHD.

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Microcephaly

• Failure of the brain to grow at a normal rate
• infections, genetic disorders, and severe
  malnutrition.
• Primary causes
• Down's syndrome
• cri du chat syndrome
• Seckel's syndrome
• Rubinstein-Taybi syndrome
• trisomy 13
• trisomy 18
• Smith-Lemli-Opitz syndrome
• Cornelia de Lange syndrome

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CRI DU CHAT Syndrome

• missing a piece of chromosome number 5.
• high-pitched cry sounds like a cat (for which the
  syndrome was named)
• Low birth weight and slow growth
• small head
• wide-set eyes
• downward slant to the eyes
• small jaw
• low set ears (may be malformed)
• skin tags just in front of the ear
• partial webbing or fusing of fingers or toes
• single line in the palm of the hand (simian
  crease)
• mental retardation
• slow or incomplete development of motor skills

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