New Insights into Autism Causes from Norwegian Study

Between 1998 and 2008, over 90,000 pregnant women in Norway participated in a significant national study examining the interplay of genetics and environmental factors in health and disease. This study, often referred to as the autism birth cohort, stands out as the first and largest of its kind.

Throughout the study, health, nutritional, and environmental data were gathered from mothers carrying more than 114,000 children during their pregnancies, specifically between 17 and 30 weeks. Follow-ups for autism diagnoses were conducted using questionnaires and national records when the children reached ages 3 and 7.

Blood samples were taken from mothers at their initial prenatal visits, typically between 17 and 21 weeks of gestation, and again on delivery day. Umbilical cord blood from infants was also collected at birth. This approach aimed to obtain precise data, minimizing biases that might arise from looking back in time.

What did we discover? For starters, blood samples from mothers of children diagnosed with autism revealed significant molecular differences related to immune and brain function as early as 17 weeks into pregnancy.

Additionally, those mothers who experienced fever during their second trimester had an elevated risk of having a child with autism, though this risk diminished if acetaminophen was taken during fever episodes. Often, these fevers came with markers of inflammation or infections in the mother’s blood, such as from the influenza or herpes virus.

Moreover, early intake of folic acid supplements, particularly prior to conception, is associated with a reduced autism risk.

When we initiated our cohort study, autism was reported to occur in about 1 in 150 children. By the time we released our final findings in 2023, this figure had escalated to 1 in 31. While this might sound alarming and suggests new environmental triggers, it’s important to note that instances of severe disability did not significantly increase. The rise in diagnoses can largely be attributed to updated criteria for autism spectrum disorder.

So, what causes autism? It’s evident that genetics play a crucial part. Identical twins, who share the same womb, tend to be more likely to both have autism compared to fraternal twins. However, environmental influences also may contribute. Genes could make certain mothers and children more susceptible to environmental impacts.

Researchers are beginning to follow intriguing leads. For instance, our findings, alongside others, suggest that some mothers may need higher folate levels during early pregnancy. There’s also a correlation with paternal age, as older fathers seem to have a connection to autism risk. Similarly, maternal age presents risks for conditions like Down syndrome.

Importantly, vaccines, including the MMR vaccine and the preservative thimerosal, have been cleared of any causal links to autism. A retrospective study that suggested a relationship in 1998 was unable to replicate those findings when retesting new samples. Furthermore, thimerosal was removed from childhood vaccines, yet autism diagnosis rates continued to rise in 2001, implying little connection.

While many individuals with autism can lead fulfilling lives, over a million people in the U.S. contend with severe autism, which often includes intellectual disabilities and a need for round-the-clock care. The annual economic burden this imposes is estimated around $450 billion.

Historically, one theory labeled “refrigerator mothers” blamed maternal emotional detachment. This notion has been utterly discredited, yet unfortunately, the idea of placing blame on mothers seems to be resurfacing.

While paracetamol overdose can lead to liver issues, banning this medication wouldn’t resolve autism. Instead, it would remove one of the few safe options for pregnant women, and, let’s be honest, it’d just add to the guilt for those who do use it.

If there’s any upside to this ongoing debate, it’s the increased attention to autism research and treatment. There’s hope that this focus prompts significant resource allocation to tackle this pressing issue in both medicine and public health.