Does Tylenol cause autism? The truth is we don't know for sure. Okay, so what do we know pretty much for sure? That women who took Tylenol during pregnancy are somewhat more likely to have an autistic child. But isn't that causation? Possibly but not necessarily.
What if carrying a fetus that becomes autistic causes the mother pain, for reasons we do not now understand? That would encourage her to take Tylenol for the pain and create the appearance of causation being Tylenol => autism when it is actually autism => pain => Tylenol.
Correlation ≠ Causation, although it suggests the possibility of causation. It is always possible some third factor is causing the other two to vary in tandem.
