You're assuming overdose rates are negatively correlated with criminalization of drugs. Have you considered the possibility that it's exactly the opposite, then when drugs are decriminalized, people can have access to better information and health care?

If you're a professional and you have alcoholism, you can get care and treatment, and it may even be paid for by your employer's health care plant. If you're addicted to cocaine, OxyContin, hydrocodone, or amphetamines, then maybe one day you OD because you never talk about it and you don't see a doctor about it, for fear of being convicted of a crime, losing your job, your health care, and ending up in prison or homeless.