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/99/4/235/13845...

I have read about this a few times. I think the main difference is in what the folks are changing: They are changing habits and lifestyle - their input - rather than changing their base personality - their output. Naturally with different input they act differently: Same for dropping a drug that affects the way you act.

And I do somewhat understand - I changed a lot of things when I moved overseas. I likely seem different: But I'm also happier and have a different knowledge base than I did a few years ago. People's expectations of me changed as well: As soon as people realize I'm not Norwegian (the English accent gives me away), it is OK if I break some social norms - those things that I had trouble grasping anyway.

I was thinking just this, too; and then fipped my opinion a few seconds ago. What I was thinking at first was "I just changed my tactics, that's all." But of course, that's what others see as our personality; our tactics. Not just our typical tactics, that is; but also what we revert to when pressed. I think I changed both, so I'm not who I was. I seem the same to me, of course... but so what. I still feeling twenty inside sometimes, or younger but that doesn't mean I am - I certainly ain't.

We are, if anything, creatures of habit. Drawn to the safety and the comfort of the similar.

Meditation is one good way to break this. Rubbing your nose endlessly in your own thoughtless patterns can be bloody embarrassing. Certainly life-changing.