Addiction, Habit, and Context: Heroin and the Vietnam War

In 1970, America was shocked by the news that 15 to 20 percent of our soldiers in Viet Nam were addicted to heroin. President Nixon set up a special office of drug policy to provide help to addicted soldiers and track what happened to them after they came home. NPR:

And so Jerome Jaffe, whom Nixon had appointed to run the new office, contacted a well-respected psychiatric researcher named Lee Robins and asked her to help with the study. He promised her unprecedented access to enlisted men in the Army so that she could get the job done.
Soon a comprehensive system was set up so that every enlisted man was tested for heroin addiction before he was allowed to return home. And in this population, Robins did find high rates of addiction: Around 20 percent of the soldiers self-identified as addicts. Those who were addicted were kept in Vietnam until they dried out. When these soldiers finally did return to their lives back in the U.S., Robins tracked them, collecting data at regular intervals. And this is where the story takes a curious turn: According to her research, the number of soldiers who continued their heroin addiction once they returned to the U.S. was shockingly low.
 "I believe the number of people who actually relapsed to heroin use in the first year was about 5 percent," Jaffe said recently from his suburban Maryland home. In other words, 95 percent of the people who were addicted in Vietnam did not become re-addicted when they returned to the United States. 

Since about 90 percent of addicts treated in America eventually relapsed after they went home, many people refused to believe Robins' results. But they have stood the test of time, and are now widely accepted. What was going on?

The answer has to do with the role of environmental cues in determining our behavior. Addicts shoot up when they are in the places where they are used to shooting up. Put them in a completely different environment, where they never see the sights or smell the smells they always associated with heroin, or hang out with the people they used to shoot up with, and they find it easy to beat the addiction.

Environmental cues may determine a great deal of our behavior. A famous and obvious example is war: there are men who could never kill in peacetime who become great killers on the battlefield. Another is that students do better on exams if they take them in the same room where they heard the lectures. We orient ourselves strongly to where we are and what we see, and this effects us on many and very deep levels.