It doesn’t stop OD, but it reduces OD because it eliminates one type of very common OD: people taking seemingly safe quantities of drugs that have been laced with fentanyl.
Statistics are fuzzy on this, because you can’t always positively determine intent, to separate accidental overdose from suicide.
The number of overdose deaths are spiking, driven by fentanyl. That is 100% fact based.
Now you have to make a qualitative judgement: I think most ODs are accidental when this is studied. Did a whole shitload of drug users just become unusually suicidal? I would say it’s safer to assume “no” unless you see evidence to the contrary.
Because I've never seen stats to back that up, other than that illegal synthetic opioids are the leading cause of OD.
Those aren't necessarily the same thing, and I would like to know more about the actual reason behind OD's.