One explanation I've read is that heavy addicts build up such a tolerance that they need dangerously high doses in the first place. If they quit for awhile like in this story, their tolerance drops and what they could previously handle now kills them.
No. It is very simple, even common, to know exactly what the dose is and still OD. Look at any prescription opioid. The labels on those bottles are very accurate. People still OD and die.
The circumstances of the overdose are important though. Many of them occur because the victim consumed it with another respiratory depressant like alcohol.
You can even OD on a known amount of the drug just by being in a different setting. Throughout my time in rehab facilities, I've met many heroin addicts with horrible stories of people close to them dying. It's a hard drug to use safely even if you know exactly how much and what you are getting, mostly because respiratory depressants cause problems when used in conjunction with so many other drugs, but also because in a heavy user, active dose over lethal dose is damn near 1:1.
Seems there is a pattern in that none of the legal easily accessible drugs are particularly easy to OD on. Cigarettes, alcohol, caffeine, weed.
Prescription drugs are more controlled because easier to OD.
It does seem like acute danger is a big factor in scheduling. There’s always the argument that drugs were scheduled out of fear and bad science. But maybe as more knowledge was gleaned over the years, it just became sensible for other reasons to leave the laws as they are.
Honestly, society is better that you don’t have a large contingent of people abstaining. And the idea that people make their own choices - I think this is greatly affected by parental attitudes. So you could easily see a big jump in a few generations from changing attitudes.
When you think about the argument for decriminalization, the issue of public safety from addiction and overdose is not very much considered. Publix safety from crime, yes. But there is inevitably an increase in risk.
What’s good at least is that we have a baseline of usage and addiction from very strict drug controls. So we can always monitor if things get out of control via more legalization.