I saw the “During the Vietnam war American troops used lots of opiates , but when the troops came home very few of them continued using” line again.
I saw it on this substack post. Go ahead and read their entire post for more detail on their theories, but proponents of the this theory usually mention community and environment as inherent to the addiction process.
That could be the case, but one GIANT missing part of this story is that all of the troops went from a place where opiates, in the form of heroin, were common (Vietnam) to a place where alcohol was common (America). The human body substitutes opiates and alcohol easily. In and of itself a dropoff in opiate use proves nothing. The troops could just switch from heroin to the culturally celebrated and easily accessible alcohol. People use this example over and over without ever considering substitution.