let me field this one: the problem is prescribed meds... "legal" only in the sense that the pharmaceutical industry has successfully killed all legislative attempts to shut down pill farms & the sleazy doctors that peddle the pharmaceutical's wares through them.
the article I posted on lobbying has an exerpt on this. since I know you're looking for an excuse to blame "personal responsibility" rather than the billion dollar pharmaceuticals making this shit, I'll bold the operative words for you:
in Tennessee in 2014 when Republican state Rep. Ryan Williams began work to stanch the flow of prescription painkillers, alarmed by a rising number of drug-addicted babies. More than 900 were born the year before, nine times the amount in 2001, many of them hooked on the prescription opioids their mothers had taken.
Doctors told Williams that part of Tennessee?s problem was a 2001 law that allowed clinicians to refuse to prescribe powerful narcotics only if they steered patients to an opioid-friendly doctor.