Autism causes and controversies: What science really says about vaccines, painkillers, and genetics

Autism diagnoses in America have skyrocketed over the last 25 years, prompting discussion about why it is growing. President Trump and Health Secretary Robert F. Kennedy Jr. recently issued a report exploring possible reasons, including vaccines and prenatal use of acetaminophen. Political attention keeps the issue at centrestage, but researchers note that autism cannot be explained by one reason, the New York Times reported.

What autism is — and is not

Autism spectrum disorder (ASD) is a wide range of developmental disorders that involve challenges with social interaction, repetitive behaviour, and differences in communication. Autism can be extremely unpredictable in terms of its severity, from mild struggle with reading people to extreme impairment that requires care for an entire lifetime. Diagnosis is based on observable behaviours, rather than tests or scans, making definition and tracking of the condition particularly difficult.

Genetics as the main cause

Scientists decades ago believed that autism might be caused by a small number of genes. Today, hundreds of genes have been linked to ASD, showing how intricate the disorder is. Predispositions in genetics and the environment both shape risk, most experts believe. Investigations have also led individuals to believe that parents' age at birth, preterm delivery, and low birth weight predispose. The image that results is not one of a single etiology but of intersecting biological and social forces.

The acetaminophen controversy

Acetaminophen, popularly known as Tylenol, has been under fire for over a decade regarding potential connections with autism when taken during pregnancy. Others indicate correlations with autism and ADHD, but others demonstrate no association when genetic and medical variables are controlled. A large Swedish study of 2.5 million children discovered that when siblings were matched against each other, the association disappeared, suggesting there were other factors at play. Medical organizations like the American College of Obstetricians and Gynaecologists continue to suggest Tylenol can be used while pregnant, though only at the lowest effective dose and frequency.

Vaccines and misinformation

Perhaps no topic is more divisive than the supposed link between vaccines and autism. The argument strengthened in the late 1990s following the publication of a discredited article by British doctor Andrew Wakefield asserting a link between the MMR vaccine and autism. The article was retracted, Wakefield's medical license was withdrawn, and subsequent large-scale studies have conclusively proven no link between vaccines and autism. Vaccines are still politically influential even after this, although scientists continue to say that vaccines are safe and crucial to public health.

Why diagnoses are rising

Prevalence of autism has increased from 1 in 150 children in 2000 to about 1 in 31 today. Some of this increase can be explained by shifts in diagnostic criteria that have over time broadened to include milder forms of the disorder such as Asperger syndrome, which is now considered a subset of ASD. Increased awareness on the part of parents, paediatricians, and teachers has also added to increasing diagnoses. School access to special services also compelled families to seek formal identification, and social media platforms such as YouTube and TikTok have driven the recognition and self-diagnosis in recent years.

A tangled picture, not an easy cause

Autism researchers agree that no single cause exists for autism. Genetics are a significant contributor, but environmental exposure, parental age at time of birth, and possibly other as-yet-unknown variables also come into play. The consistent rise in diagnoses is as much due to medical, cultural, and social as biological changes. Easy explanations of vaccines or analgesics, as experts caution, take away from the complexity of the condition and the necessity of support for those who live with autism and their families.