causal

The group did not determine a causal relationship between the drug and autism, or suggest barring the drug altogether, she said.

"To be clear, while an association between acetaminophen and autism has been described in many studies, a causal relationship has not been established and there are contrary studies in the scientific literature," the FDA wrote.

It compared autistic children with their siblings to control for genetic factors, and found no evidence to support a causal link between autism and the use of the painkiller.

The announcement was met with dismay from autism researchers and advocates who said that research thus far into causal links between acetaminophen and autism has turned up minimal evidence.

"There is no robust evidence or convincing studies to suggest there is any causal relationship," said Monique Botha, a professor in social and developmental psychology at Durham University.