Causes and Risk Factors of Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) does not arise from a single cause; rather, it results from the combined influence of genetic and environmental factors. Recent literature indicates that genetic variations, parental age, maternal health during pregnancy, and birth complications are all associated with increased risk.

Genetic Factors

• High heritability: Twin studies show that genetic factors can account for up to 80–90% of the risk.
• Associated genes: NRXN1, CNTNAP2, and SHANK3, which are involved in brain development and synaptic function.
• Genetic syndromes: Conditions such as Fragile X syndrome and tuberous sclerosis are linked to increased risk of ASD.

Environmental Factors

• Maternal health during pregnancy: Advanced maternal age (>35 years), gestational diabetes, gestational hypertension, obesity, or metabolic syndrome are all associated with increased risk.
• Drug exposure: Prenatal use of the antiepileptic drug valproate has been confirmed to be associated with increased risk.
• Infection and immunity: Maternal infections or immune abnormalities during pregnancy may interfere with fetal brain development.
• Birth complications: Premature birth, low birth weight, and hypoxia are all associated with ASD risk.

High-Risk Factors

• Sex: Boys are affected about 3–4 times more often than girls.
• Parental age: Children of fathers over 50 years old have a significantly increased risk.
• Family history: If there is already one affected child in the family, the risk for siblings is markedly higher.
• Maternal health problems: Conditions such as diabetes, thyroid disease, or obesity during pregnancy are linked to increased risk.

Common Misconceptions

• The World Health Organization and multiple large-scale studies have clearly refuted any causal relationship between vaccines and ASD.

Summary

The causes of Autism Spectrum Disorder are the result of multiple interacting factors: genetic predisposition provides susceptibility, while maternal health, environmental exposures, and birth complications further influence risk. High-risk factors include male sex, family history, advanced parental age, and maternal health problems. Understanding these factors supports early identification and intervention, thereby improving quality of life for patients.