In a massive study looking at more than two million individuals, scientists have failed to find any meaningful link between the use of opioid painkillers and the prevalence of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD), challenging earlier research suggesting otherwise.

Previous studies have suggested that children exposed to opioid pain medications while in the womb have higher rates of autism spectrum disorder (ASD) and attention- deficit/hyperactivity disorder (ADHD), but a new study finds that any increased risk could be explained by other factors.