What Neuroscientists Now Know About Autism

A deep dive into the latest research and big questions remaining about autism.

There’s a reason most of us don’t recall growing up with as many autistic kids as there are now: Many more children are diagnosed with autism spectrum disorder today than ever before. According to the Centers for Disease Control and Prevention, autism now affects 1 in 59 children, compared to 1 in 88 kids in 2008 and 1 in 150 children in 2000.

Part of this astonishing increase is due to heightened awareness of the disorder and more accurate diagnoses. Whether there are other factors at play — such as environmental exposures or the fact that parents are having babies later in life, which research shows increases the odds of autism — is still a matter of debate.

“There is no one autism.”

What remains far murkier than prevalence is the basic biological cause of this disorder. That’s partly because autism is actually a constellation of neurological conditions, each of which hinders communication, social skills, motor skills, and behavior. “There is no one autism,” says Dr. Daniel Weinberger, director and CEO of the Lieber Institute for Brain Development at Johns Hopkins University. “The term is used to describe many different disorders of early childhood that have several characteristics and manifestations, the main one being problems in developing social connections.” Kids usually begin showing signs as toddlers, and the majority are diagnosed around age four.

The Genetic Blueprint

Most forms of autism appear to be rooted in genetics — or, more specifically, inherited variations of one or more genes. “In most cases, it is likely caused by combinations of many, many genes that influence brain development,” Weinberger says. “However, genes don’t know anything about social interactions or anxiety or outward behavior. They are only responsible for two things: fixed traits, such as height and hair color, and the behavior of cells.” The DNA in each cell is like a factory foreman, he explains, constantly ordering that cell how to operate.

So in other words, when a child inherits a gene variation, that gene affects only the function of a cell. How then does this impact how an autistic child thinks, acts and relates to others? This is explained by understanding that each does not act in isolation. As part of the entire genetics or “genome” of a person, they interact with each other.

“Following the blueprint of their genomes, cells talk to and build relationships with one another as a child develops,” Weinberger says. “They form networks with other cells and grow up to become different structures in the brain like the hippocampus and thalamus. While cells process molecular information, the networks they belong to process cognitive, social, and emotional information.”

Nature Versus Nurture

Environmental factors such as having supportive parents, eating a nutritious diet, and attending a stellar school actually have less influence on autistic children’s behavior than you might think. According to Weinberger, there is no science showing that a healthy environment will override the effects of a genetic mutation. Yet despite the lack of scientific proof, he believes that all human behavior can be modified to a certain degree. “But the boundaries, the limits around which parents can make a difference, are very restricted,” Weinberger says.

“Those first five years are a critical period in forming the capacity to negotiate the more complicated times of life down the road.”

What is very clear, though, is that kids exposed to severe stress in their first five years tend to have more social, mental, and physical stressors later in life. “Drug-taking behavior, diabetes, body weight, hypertension — the probability of all of these things is increased in people who’ve experienced extreme childhood stress,” Weinberger says. “As Freud told us, those first five years are a critical period in forming the capacity to negotiate the more complicated times of life down the road.”

What this means for a child with autism is that, while a loving mom and dad, food on the table, and a structured family life may not override biology, these factors potentially lower the odds of developing certain health issues as adults.

The Pitt-Hopkins Treatment

Since autism spectrum disorder is so broad, the Lieber Institute for Brain Development hopes to make progress helping affected kids by first focusing on one very distinct type of autism: Pitt-Hopkins syndrome. While only occurring in a few thousand kids in the U.S., this rare syndrome holds great potential to unlock secrets for understanding other types of autism. “Pitt-Hopkins is just one small piece of the pie, but we chose to study it because we know exactly what causes it, whereas in other forms of autism we are still determining the underlying genetic causes,” Weinberger says. This syndrome is caused by a single genetic mutation that prevents the TCF4 gene from making a protein that is important in cell function. As a result, the cells that rely on that protein function abnormally.

“Because it is a very discreet mutation found on one gene, we can build models in the lab of Pitt-Hopkins symptoms that reflect the exact cause,” Weinberger says. These models allow Lieber Institute scientists to investigate exactly how the genetic mutation plays out in brain development to see if they can mitigate some of the damage.

“We want to find out what is going wrong and try to correct it,” Weinberger says. “Many people think you can correct the gene, but that is very hard and risky to do. We took a different strategy: assuming you can’t change the genome, let’s try to normalize the behavior of the brain from what the genome is doing to it.”

Using these models, Lieber researchers discovered that when these cells were stimulated, they acted very abnormally. “Behavior is disrupted because the cells aren’t firing properly,” Weinberger explains. His team traced the problem to a change in a particular protein that makes up a sodium ion channel on the cell’s membrane. This channel serves as a gate which allows salt to move in and out of cells. They think that this mutated ion channel is partially responsible for behavioral changes in kids with Pitt-Hopkins.

With this knowledge, the team looked to find a drug that could block the change in the ion channel to see whether cells are affected. “We found that by targeting the ion channel with a drug — we restore the function of the cells,” Weinberger says. “We are probably a year away from seeing the drug tested in humans, but this will be the first potential treatment for autism based on understanding a specific cellular mechanism that leads to Pitt Hopkins Syndrome, a rare form of autism.”

Weinberger insists that this drug will not cure Pitt-Hopkins syndrome because the mutation likely affects more than just the ion channel. However, he believes that kids who take the drug will be better off, because the neurons in their brain will function more normally.

Although the Lieber Institute’s work focuses on this form of autism, it signals hope not just for kids with Pitt-Hopkins and their families. A better understanding of this one type of autism paves the way for similar advancements for other types of autism spectrum disorder down the road.

How to Know If Your Child Has Autism

Signs of autism spectrum disorder typically appear within the first few years of a child’s life. But since these tots usually learn to sit, crawl, and walk right along with other kids their age, parents may not notice their delays in speech, social interactions, learning, or play — or they might brush them off as no big deal. Early detection and interventions are crucial, though, because they can improve outcomes, sometimes significantly. Some signs to look for include:

  • No big smiles or other warm, joyful expressions by six months.
  • No back-and-forth sharing of sounds, smiles, or other facial expressions by nine months.
  • No babbling by 12 months.
  • No back-and-forth gestures such as pointing, showing, reaching, or waving by 12 months.
  • No words by 16 months.
  • No meaningful, two-word phrases (not including imitating or repeating) by 24 months.
  • Any loss of speech, babbling, or social skills at any age.

These are by no means definitive signs of a child with autism and if you have concerns you should see a clinician. You can also learn more by visiting the CDC’s Autism Spectrum Disorder Resource Page.

This story was produced in partnership with the Lieber Institute for Brain Development, whose mission is to translate genetic insights into next generation treatments.