What year pharmacy school are you in, Sosoo? I'm assuming you have *not* had any classes in statistical analysis yet? To help you paraphrase, the article says that 1/2 of opioid overdoses were people on Medicaid, this does NOT mean that 1/2 of people on Medicaid who take opioid's will overdose. Think of it this way, the article's statement would still be true, if there were 5,000 opioid prescriptions dispensed to Medicaid patients & there had only been 2 opioid overdoses that year, and 1 of the opioid doses was a Medicaid patient.
In other words, this article points out a correlation....whether or not this correlation actually means anything, we don't know. Just like how there is a correlation between increased sells of ice cream and increased number of rapes, the correlation does NOT mean that ice cream causes people to become rapists. The article doesn't tell us how many of these overdoses were accidental and how many were intentional. The article doesn't tell us how many of these overdoses were in people who had a terminal condition. The article doesn't tell us how many of these overdoses were in people with chronic health problems & how many were in people being treated for acute pain. This article doesn't tell us how many people overdose on prescriptions from ER doctors as opposed to pain specialists (ER doctors aren't going to have a complete health picture of the patient & may be unaware of the patient doctor shopping, Medicaid patients are more likely to use the ER because they have limited access to specialists and also just because they can.) As others have pointed out, people with chronic health problems are less likely to work & more likely to be on Medicaid--this is a known skewer and would have to be accounted for before any statistical conclusions can be drawn.
It's impossible to answer any of your questions, based on this article, because there are too many unknown variables. The article points out that opioid death's are higher in WA, than in other states. But is there a legitimate reason why? Are there population differences between WA and other states that would account for there being more overdoses? What would be the difference between health care providers in WA, as opposed to other states, that would cause the health care providers to contribute to more deaths in WA? Is there a higher rate of depression in WA (maybe from the rainy weather?) that would be a contributor to there being more overdoses?