Search for '[acetaminophen/paracetamol/tylenol] study' every few years and you'll find something new. The latest seems to be strong observational evidence that it drives neurodevelopmental issues, including ADHD/autism, when taken during pregnancy. This is being pushed back against hard because this has led to Johnson & Johnson being sued by hundreds of people claiming they already knew this, setting them up to become the next big tobacco if they lose.
The link is very strong and so big pharam's defense is that it's not not tylenol, but having an issue for where tylenol might be needed, that is causing the issues. A bizarrely excellent and balanced article on the issue is available here. [1]
