There is little research on chiropractic’s benefit for autistic people. A systematic review of the literature in 2016 found only one collection of cases, 11 individual case reports, and one clinical trial with 14 participants but no controls. The researchers who compiled the review deemed the single trial of poor quality and the reporting in the collection of cases “insufficient.” Though the case reports all described some benefit, the researchers said that the evidence was too scarce and too weak to be reliable. A 2010 analysis reached the same conclusion. “Inconclusive safety, inconclusive efficacy: Discourage,” wrote its authors.

Nor is evidence likely to be forthcoming anytime soon. Experts note that there is no plausible explanation for how chiropractic treatments could have any effect on autism. “If I heard a parent telling me that that was what they were pursuing for a child, I wouldn’t hesitate to tell them that that is nonsense,” says Suzanne Lewis, the chair of the advisory committee for the advocacy group Autism Canada. “You can’t change brain function by moving suture plates or cranial plates or dropping the soft palate or whatever else they might be promoting,” she says. “There’s no evidence that it makes any benefit—and at best, you’re lucky that it doesn’t cause harm.”

How exactly did chiropractors get the idea that moving vertebrae could alter the course of a condition such as autism?

The explanation harks back to the earliest days of the profession. Chiropractic was invented in the late 1800s by Daniel David Palmer, a former grocer and deeply religious “magnetic healer.” Palmer subscribed to “vitalism,” a philosophy espousing the idea that a vital force animates all living things. He asserted that this force, which he called “Innate,” flows from God to the body via nerves passing through the spine. He said this force keeps the body in good health. And he taught that blockages in the spine, or “subluxations,” can degrade or stop its flow and lead to disease. In Palmer’s view, chiropractors could remove subluxations by adjusting the vertebrae of the spine, allowing the body to heal itself of anything from deafness to heart disease.

Mainstream medicine has advanced dramatically since Palmer’s time, but his prescientific, vitalist ideas continue to thrive within the chiropractic community. As much as 30 percent of contemporary chiropractors in North America proudly practice in the vitalist tradition. As such, they view autism as one of dozens of conditions they can treat by “removing blockages.”

These chiropractors are not just at the fringes of the field. Cliff Hardick—the past president and a current member of the regulatory board that oversees more than 5,000 chiropractors in Ontario, Canada—is a dyed-in-the-wool vitalist. In a 2017 speech to chiropractors at a conference in Atlanta, he boasted of his success in treating children with developmental delays: “We get those kids coming in. They’ve been in speech therapy for nine months and they can say three words, and after just four or five adjustments over about two or three weeks, their therapist is saying, ‘I can’t figure out what’s going on; they’re starting to build sentences.’ That’s what chiropractic is! That’s what chiropractic is!”