From the Guidelines
The exact causes of autism are not fully understood, but it's likely due to a combination of genetic and environmental factors, with the most recent evidence suggesting that environmental chemicals and gene-environment interactions contribute to the etiology of the disorder 1. Current research suggests autism spectrum disorder (ASD) develops from:
- Genetic factors: Certain genes or gene mutations may increase the risk, with studies identifying many genetic factors that increase the risk of ASD, including rare mutations with large effect 1.
- Environmental influences: Factors during pregnancy or early childhood may play a role, such as advanced parental age, maternal illness during pregnancy, or complications during birth, with environmental chemicals, including pesticides, heavy metals, bisphenol A (BPA), and phthalates, potentially contributing to the development of ASD 1.
- Brain development differences: People with autism often show differences in brain structure and function, with studies suggesting that subtle signs of autism can be detected as early as 9 months 1.
- Neurological factors: Imbalances in neurotransmitters or connectivity issues between different brain regions may contribute, with the developing endocrine system potentially playing a role in the etiology of autism, particularly in males who are disproportionately affected 1. It's essential to note that vaccines do not cause autism, a misconception thoroughly debunked by numerous scientific studies. While we can't prevent autism, early diagnosis and intervention can significantly improve outcomes, with a multidisciplinary assessment, including medical, psychological, communication, and occupational therapy evaluations, being crucial for diagnosis and treatment planning 1. Understanding autism as a complex neurodevelopmental condition helps explain why there's no single cause or cure, but rather a range of potential contributing factors and management strategies, with genetic testing, including chromosomal microarray analysis, being warranted and clinically indicated for all suspected cases of ASD 1.
From the Research
Causes of Autism Spectrum Disorder (ASD)
The causes of Autism Spectrum Disorder (ASD) are complex and multifaceted. According to 2, ASD is not a disease but a syndrome with multiple nongenetic and genetic causes. The exact causes of ASD are still not fully understood, but research suggests that it is a result of interactions between genetic, epigenetic, and environmental factors.
Genetic Factors
- Genetic factors are thought to play a significant role in the development of ASD, with studies suggesting that multiple genes are involved 2, 3, 4.
- Twin studies have shown that the concordance rate for ASD is higher in monozygotic twins than in dizygotic twins, indicating a strong genetic component 2.
- Specific genetic syndromes, such as Rett syndrome, fragile X syndrome, and tuberous sclerosis complex, have been linked to ASD 2, 4.
Environmental Factors
- Environmental factors, such as toxic exposures, teratogens, perinatal insults, and prenatal infections, may also contribute to the development of ASD, although the evidence is limited 2.
- Immunizations with the measles-mumps-rubella vaccine have been shown not to be responsible for the surge in autism cases 2.
Complexity of ASD
- ASD is a heterogeneous disorder, and it is unlikely that there will be a single explanation for the diverse symptoms defining autism 5.
- The etiology of ASD involves a complex interplay between inheritance and environmental factors influenced by epigenetics 4.
- Behavioral and psychiatric conditions in autism are impacted by genetics, which can influence clinical evaluations, counseling, diagnoses, therapeutic interventions, and treatment approaches 4.