I get a bit antsy when I see big unexpected flips in numbers like that and think Johann Hari oversimplifies the case. That was the initial study, a followup wi

I get a bit antsy when I see big unexpected flips in numbers like that and think Johann Hari oversimplifies the case. That was the initial study, a followup with 943 Vietnam vets by the original researcher Lee Robins found that: "In the 8- to 12-month period since their return, about 10% had some experience with opiates, but less than 1% had shown signs of opiate dependence. In the “drug positive” sample, three-quarters felt they had been addicted to narcotics in Vietnam. After return, one-third had some experience with opiates, but only 7% showed signs of dependence. Rather than giving up drugs altogether, many had shifted from heroin to amphetamines or barbiturates. Nevertheless, almost none expressed a desire for treatment." [1] So the point still stands that environmental factors affect patterns of drug abuse, but it is complicated by two things, the numbers are less dramatic than "95% simply stopped" and also would raise one concern that addiction was clinically tested on return but was self-reported in the interviews. https://academic.oup.com/aje/article-abstract/99/4/235/138453/DRUG-USE-BY-U-S-ARMY-ENLISTED-MEN-IN-VIETNAM-A https://academic.oup.com/aje/article-abstract/99/4/235/13845...