Harm Reduction vs Abstinence Models

I‌‍‍‌‌‍‌‌‌‌‌‍‍‍‌‌‌‌‍n no more than 2 paragraphs, please compare the harm reduction approach for substance use with the traditional abstinence model in the context of supporting people with o‌‍‍‌‌‍‌‌‌‌‌‍‍‍‌‌‌‌‍pioid use problems. Are there overlaps between these approaches? Are there major differences between them? Are there ways in which these approaches can be complimentary?‌‍‍‌‌‍‌‌‌‌‌‍‍‍‌‌‌‌‍