As requests for testing embryos for autism skyrocket, doctors search for the complex causes and make the case for neurodiversity.

Women have long known that their biological clocks are ticking, with their fertility beginning to decrease rapidly in their mid-30s. On the other hand, there’s never seemed to be an age limit on when men can become fathers.

Doctors agree that women age 35 and older are of advanced maternal age (AMA), but the understanding of risks associated with older fathers is still evolving. Advanced paternal age (APA), usually defined as a biological father over 40, is an increasingly popular topic as older parents become more common.

Studies show that children with older fathers are at a greater risk for certain disorders, specifically autism and attention deficit hyperactivity disorder (ADHD).

A 2011 study in Molecular Psychiatry of over 5.7 million children in five countries found a link between older fathers and autism.

The researchers showed that the chance of having a child with autism was 28 percent higher among fathers who were in their 40s, and 66 percent higher for men in their 50s, compared to fathers younger than 30.

Scientists have suggested that aging sperm, which has a higher number of mutations that are also passed on to the child, may be a key player in the link between older fathers and increased risk of autism.

Dr. Jason Kovac, an endocrinologist at IU Health, believes that the older sperm theory is still up for debate. “It’s hard to know exactly if older sperm is worse, since there are so many variables besides age in these studies linking older fathers and autism,” he pointed out. Some of these variables include lifestyle, diet, and tobacco, alcohol, and drug use.

Read more: A day in the life of an autism parent »

The Centers for Disease Control and Prevention estimates that 1 in 68 children in the United States have autism: 1 in 42 boys and 1 in 189 girls.

“Autism is what we call ‘a spectral disorder.’ It exists on a spectrum, from missing social cues, which possibly indicates something like Asperger’s, to a serious case where the person with autism can’t function in society and has to be institutionalized,” explained Dr. Brian Levine, a New York City reproductive endocrinologist.

The prevalence of autism has doubled in the United States since 2000, and it’s rapidly rising globally.

A 2015 analysis of Danish cases found that 60 percent of the increase in autism rates can be attributed to increased awareness of autism and an expanding medical definition of the disorder. However, that leaves 40 percent of new cases unexplained, indicating a true increase.

While researchers are finding links between autism and specific factors, no one cause is obvious for a reason. “Autism is likely a combination of nature, which means you can inherit it, nurture — what you feed your child and how you raise them — and the diet and health of the mother,” Dr. Levine told Healthline.

Read more: Not even siblings with autism share the same genetic risk factors »

A 2016 paper published in Nature Genetics says we shouldn’t be so quick to blame autism on older sperm.

Scientists discovered that the increased number of mutations in older men’s sperm isn’t high enough to explain the full extent of the higher risk of autism in older fathers’ kids.

Instead, the scientists suggested that older men who have or are at risk for psychiatric disorders, like autism, tend to have children later in life — and genetically pass the disorder on to their kids.

“Maybe older men that have these soft signs of autism marry later in life — these roots are heritable,” Dr. Levine said, noting that how specifically the autism gene is passed on is still unknown.

Autism isn’t inherited in a simple way. Even siblings who both have autism have different autism-related genetic mutations.

“The flaw of the study is that we don’t know what these kids’ lives look like, such as how much influential interaction the parents are having with the child. Many of these studies are using correlation without causation,” Dr. Levine said.

This explanation plays into the Silicon Valley theory expressed in a 2001 Wired article, which suggested that tech hubs attract a high number of “geeks” that are or could be diagnosed with Asperger’s, or mild autism.

This may reveal why California scientists have identified clusters of autism around San Francisco, Los Angeles, and eight other California cities, where children are twice as likely to have the disorder.

Furthering this theory, a recent study created a “geek index” and measured 15,000 pairs of twins for IQ, social aloofness, and ability to focus intently on one subject of interest.

Researchers found that advanced paternal age led to geekier sons according to the index. The link wasn’t present in daughters.

While a high IQ and social awkwardness are different from true autism, the researchers noted that it’s possible that some of the traits overlap. Boys who ranked high on the geek index went on to do better in school, especially in science, technology, engineering, and math (STEM) subjects. These are in-demand skills in tech hubs.

“[Younger men] that work in the tech industry might not be putting having a family off by choice. Perhaps they are having a harder time finding suitable partnership,” Dr. Kovac suggested. So, these men that are possibly on the autism spectrum pass on those traits to their children as older dads.

It’s also possible that geek culture has glorified oddballs, and whatever age the dads are, this group is passing along the soft features of autism at a higher rate.

Read more: New autism drug shows promising results »

Nearly 100 genes have been linked to autism or its telltale signs, but scientists believe that no one gene mutation results in the disorder.

To be able to determine the causes of autism and, in the future, test for it, Dr. Levine told Healthline that studies need to look at three areas.

“To test for autism, first we need to genetically sequence all the children that have the disease, then look for genetic imprinting and soft changes — genes that are being forced to be expressed,” Dr. Levine explained.

The gene can be expressed in different ways depending on which parent the child got the gene from.

“Second: Do a home visit. What does the child’s life look life? Are they being given way more sugar than other children? Are they spending a lot of time on iPads?” Dr. Levine asked, mentioning the recent study linking iPads to speech delays.

iPad and smartphone use by children has also been shown to lead to social and emotional development problems.

Dr. Levin’s third recommendation: “Check out the in utero health of the mother. Is she sedentary or active? For example, a young woman who’s working may be moving more, so more blood is getting to the uterine wall.”

Studies have shown links between a mother’s health and autism. A 2016 study found that excessive levels of folate during pregnancy tripled the risk for a child with autism.

“Often the symptoms of autism are neurological soft signs that can’t be easily diagnosed in pregnancy,” Dr. Levine said of prenatal screening of the disorder.

Still, parents undergoing in vitro fertilization (IVF) are eager to screen for autism, but the technology to do so still doesn’t exist. “We still cannot test embryos for autism, but I can see that happening once we identify a causative agent in the gene,” Dr. Levine clarified.

Start-ups are eager to deliver on the requests of families undergoing IVF that want to add autism to the list of diseases to screen their embryos for.

Dr. Aimee Eyvazzadeh, a reproductive endocrinologist based in the San Francisco area, said that patients ask her to test their embryos for autism all the time. She said the reality isn’t far off. “It’s about a year and a half away, but there is a company that’s going to be testing embryos genetically for autism.”

Dr. Eyvazzadeh is currently able to perform a screening for high-risk autism genes on sperm.

If prospective parents find out the father carries some high-risk genes that are significantly associated with autism, it allows them to decide whether or not to use a sperm donor before they create embryos.

The Reproductive Technology Council of Western Australia uses a different work-around for prenatal screenings of autism before the test exists. It allows women going through IVF who are at a very high risk of having a child with autism to be implanted with female embryos only, since the prevalence of the disorder in males is much higher.

“Neurodiversity is the idea that neurological differences like autism and ADHD are the result of normal, natural variation in the human genome,” according to John Elder Robison, a neurodiversity scholar at the College of William & Mary who has Asperger’s himself.

Robison noted that “Studies show that 20 percent of high school students are in some way neurodiverse.”

In a culture that celebrates innovation, companies are discovering that there are advantages to having autistic employees, who see and solve problems differently than neurotypical employees.

Several prominent companies like SAP, JP Morgan Chase, and IBM are even starting outreach and hiring initiatives to recruit employees with autism.

They realize neurodiverse employees bring unique, and often exceptional, skills and problem-solving methods to the workforce. Between increases in productivity and innovative ideas, companies see employees on the autism spectrum as a competitive advantage.

So rather than view difference as a disorder, neurodiversity advocates see the spectrum of neurological functioning as our reality. They believe that including people on the spectrum in schools and companies will allow us to tap into the full extent of the human intellect.

Dr. Levine subscribes to this viewpoint when taking to patients who request a prenatal screening for autism. “Everyone has a different definition of normal. I encourage people to use ‘in the realm of normal’ or ‘just like everyone else.’ Steve Jobs probably wasn’t ever described as normal, but he’s one of the most successful men of our time.”