Most young adults have no pressing need for healthcare except possibly birth-control pills for the young women (since those require a prescription in the US) and if the millions of young adults in the US who have become addicts during this crisis had unmet health-care needs at a significantly higher rate than their counterparts who did not become addicts, addiction researchers would almost certainly have noticed by now, and I probably would've heard about it from journalists who cover the issue.
Oh, yeah, I’m not saying that healthcare is the only factor or even the most important factor, just that it is relevant (and it does seem to be where the US opioid crisis _started_; oxycodone and similar were made available in ludicrous quantities as a substitute for actual medical care).
Granted, it is probably much harder to put the genie back in the bottle now it’s out there.
Anecdotally: cardiologist, inpatient rehab, dental work, maintenance medication, labs/blood work, mental health meds/counseling, ER visits and ambulance rides, and more.
These are things that non-addict young people do not usually need unless they’re big athletes or suffer from serious trauma.
Having access to these things also improves the likelihood of a full recovery from addiction (IMO).