@demlion has mentioned the book, "Dreamland" countless times before. This book illustrates where this bogus 'study' came from. It really wasn't a study at all.
There was a doctor (forget his name) in Boston I believe. He sent a very brief note to the New England Journal of Medicine. His note (paraphrased) said to the effect that in his experience with a very small number of patients in a hospital setting, he did not observe addiction in patients being administered opiates. End of note.
The NEJOM ran this note in a column where they have all kinds of miscellaneous observations by doctors on all kinds of topics. These are not studies at all - it's like water cooler conversation where a doctor will say to the effect of 'I did X with Patient Y and I had Z result'.
Purdue Pharma and others glommed onto this and built their entire marketing effort around it. Hey - The NEJOM says our meds aren't addictive!
That is obviously deceptive sales practices, and it is certainly actionable. Purdue is going to have a lot of 'splainin' to do.