Which of the following is true regarding causes of intellectual disabilities?

Question

BlackTom AI · Accepted Answer

Prenatal exposure to teratogens can disrupt organogenesis and brain development, increasing the risk that a child will develop an intellectual disability. Teratogens include alcohol (leading to fetal alcohol spectrum disorders), certain prescription drugs (e.g., some anticonvulsants), maternal infections (rubella, cytomegalovirus, toxoplasmosis), environmental toxins (lead, mercury), and radiation; many of these interfere with neural proliferation, migration, synaptogenesis, or myelination during gestation.

1. Relevant knowledge points and concepts
- Intellectual disability (ID) has multiple etiologies: genetic/chromosomal conditions (e.g., Down syndrome, Fragile X), prenatal factors (teratogens, maternal illness), perinatal complications (hypoxia, prematurity), and postnatal causes (trauma, infection, severe deprivation).  
- Teratogens are agents that produce malformations or functional deficits when exposure occurs during fetal development. Fetal Alcohol Spectrum Disorders are a well-established preventable cause of intellectual impairment.

2. Step-by-step reasoning
- Identify known risk categories for ID: genetic, prenatal environmental, perinatal, postnatal, and unknown.  
- Evaluate the statement about prenatal teratogen exposure: because teratogens can alter brain development, prenatal exposure plausibly and empirically increases risk for ID.  
- Compare with alternative choices: some alternatives assert small genetic contribution, universal identifiability of cause, or that Down syndrome is the majority cause—each conflicts with epidemiologic and clinical knowledge.

3. Calculations
- No numerical calculations are required for this conceptual question.

4. Why the correct answer is correct
- Empirical evidence supports that prenatal teratogens (notably alcohol) are risk factors that increase the likelihood of intellectual disability; many guidelines emphasize teratogen avoidance to reduce ID risk.

5. Why other options are incorrect
- “Genetic and chromosomal disorders are responsible for a very small percentage” is false: genetic/chromosomal causes are a substantial and important category of ID.  
- “All cases of intellectual disability have an identifiable cause” is false: a significant fraction remain idiopathic despite evaluation.  
- “Down Syndrome accounts for the majority of cases” is false: Down syndrome is a common known genetic cause but does not represent the majority of all ID cases.

6. Conclusion
The correct choice is: “Prenatal exposure to teratogens may place the child at risk for experiences that may increase the likelihood of intellectual disability.” This matches the provided answer.

Which of the following is true regarding causes of intellectual disabilities?单项选择题

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