Yes and no. Very few people get started with a legitimate prescription. The typical opioid OD happens to someone who had other substance abuse and mental health problems and at some point started taking resold/stolen prescription opioids. Until fentanyl flooded the market most ODs were multi-substance and often(some 85%+ in places where coroners checked if memory serves) involved a LOT of alcohol. Now, its often just fentanyl, which is hard to dose correctly especially if you've recently tried to quit.