In his 1999 study of natural recovery from alcohol abuse among Navajo Indians, the anthropologist Gilbert Quintero and colleagues at the University of Rochester in New York found that: ‘One of the most persistent and formative influences organising narratives of “ageing out” were the responsibilities and role demands connected to raising children.’ The more that individuals came to embrace their Navajo heritage, the more they expressed a sense that drinking simply didn’t fit anymore. Abstaining from alcohol use became a means of identifying with their culture. Similarly, while binge-drinking is a notorious and often troubling rite of passage for many young Americans, the behaviour – outside of specific contexts – has an expiration date. As we age and seek to fit into cultural moulds, we often change what we do.

My own experience of ageing out is what drew me to study drug use in the first place. Almost 15 years ago, before it had ever occurred to me that one could make a career from studying addiction, I quit meth for the last time. I’d just graduated from the University of California, Los Angeles with a bachelor’s degree in anthropology, and it was my first week as a full-time ‘reservationist’ at a hot new three-star restaurant in New York.

When my roommate and I decided to move across the country, I’d assumed my five-year amphetamine habit would stick close. After all, I’d brought it from the sunny suburbs of Phoenix to the sooty skies of Los Angeles. But on one chilly East Coast morning in early autumn, as the tedium of a nine-to-five schedule and public transit commute set in, I started to tire at the prospect of another night awake. For the first time, I wanted to stop the speed cycle before it started.