US Health Secretary Robert F Kennedy Jr has promised to start a big testing and research project to find the cause of autism in five months.

Experts, however, said that finding the cause of autism – which is a complex condition studied for many years – will not be easy. They said the plan is not practical and may be wrong.

Kennedy has earlier supported false ideas that vaccines cause autism. He said during a cabinet meeting on Thursday that a US research project will include hundreds of scientists from around the world.

"By September, we will know what caused the autism epidemic, and we’ll be able to remove those causes," Kennedy said.

Autism cases have gone up a lot since the year 2000, according to government data. In 2020, 2.77% of 8-year-old children in the US had autism, according to the Centers for Disease Control and Prevention (CDC).

Scientists say part of the rise is because people now know more about autism, and the definition of the condition has become broader. Researchers are also studying environmental causes.

The US National Institutes of Health (NIH), a government group, spends over $300 million every year to study autism.

NIH says some possible causes include exposure to pesticides or air pollution before birth, being born early or with low weight, health problems in the mother, and older parents having children.

Kennedy did not give details about how the research will be done or how much money will be spent on it.

Since he became health secretary two months ago, Kennedy has cut the budget of the Department of Health and Human Services (HHS). HHS includes the NIH, CDC, and other groups that protect food and drug safety and study diseases.

Kennedy said in an interview with Fox News that vaccines will be studied, but they will also look at everything. “Everything is on the table – our food system, our water, our air, different parenting styles – all the changes that could have caused this rise in autism,” he said.

The Autism Society of America called Kennedy’s plan “harmful, misleading, and unrealistic.”

“It (autism) is not a chronic illness or a contagious disease,” the society said.

Christopher Banks, the group’s president, said he is not sure the research will be honest. He also said blaming the environment alone is a wrong theory that spreads bad ideas, puts public health at risk, and takes attention away from the real needs of autistic people.

People are also worried because Kennedy hired David Geier to study vaccines and autism. Some people call Geier a conspiracy theorist.

On Thursday, Democrats in the US House of Representatives sent a letter to HHS saying they are very worried about Kennedy choosing Geier, who they called “a biased and discredited individual.”

Geier does not have a medical license. The state of Maryland fined him for acting like a doctor without a license and giving dangerous treatments to autistic children.

The false idea that vaccines cause autism became popular after a paper was published in 1998 by British doctor Andrew Wakefield in a medical journal called The Lancet.

Later, people found out Wakefield had a financial interest in the study and had lied about the results. The UK's General Medical Council said he made up the data, and the paper was removed.