Nearly 50,000 died of opioid overdose during 2018. What I want is, textbook or research paper that go deeper into these numbers and analyze them. Like, were all deaths attributed to overdose due to addiction or some of them were due to medication error, iatrogenic in other words? Maybe 1000 died due to iatrogenic opioid overdose? So, instead of listing 50,000, I want analysis, deep analysis of this number?