Many parents are turning to unproven treatments to help their kids with autism and other developmental delays, a new study finds, including some methods that carry serious risks.

Some 40 percent of children with autism are using complementary and alternative medicine — including everything from meditation to homeopathic remedies, probiotics, alternative diets and riskier therapies like chelation — according to findings published this month in the Journal of Behavioral and Developmental Pediatrics.

In a study of nearly 600 California kids ages 2 to 5 with autism or developmental delay, researchers asked parents about the types of current and past services their child received. They found that 40 percent of those with autism and 30 percent of kids with developmental delay had used some type of complementary and alternative medicine. The most popular were dietary supplements and a gluten-free, casein-free diet.

In many cases, parents reported using complementary and alternative medicine alongside more conventional treatments like behavior, speech or occupational therapy.

Among parents of kids with autism, nearly 9 percent reported using alternative treatments the researchers considered to be “invasive, disproven or potentially unsafe” including chelation, anti-fungal medications and vitamin B-12 injections.

Parents with higher levels of education and income were more likely to use alternative treatments, the study found. What’s more, kids receiving over 20 hours per week of conventional services more frequently used the unproven approaches including those considered potentially unsafe.

“It does not appear that families use complementary and alternative treatments due to the lack of availability of conventional services, as has been suggested by other research,” said Robin Hansen of the University of California, Davis MIND Institute who led the study. “Rather, they use the treatments in addition to conventional approaches.”

Given the popularity of these alternative methods, the researchers said that doctors and other professionals need to take a more active role in talking to families about the pros and cons of various treatment options.