At Metropolitan State College of Denver, Harvey Milkman was instrumental in developing the idea that people were getting addicted to changes in brain chemistry. Kids who were “active confronters” were after a rush – they’d get it by stealing hubcaps and radios and later cars, or through stimulant drugs. Alcohol also alters brain chemistry, of course. It’s a sedative but it sedates the brain’s control first, which can remove inhibitions and, in limited doses, reduce anxiety.

“People can get addicted to drink, cars, money, sex, calories, cocaine – whatever,” says Milkman. “The idea of behavioural addiction became our trademark.”

This idea spawned another: “Why not orchestrate a social movement around natural highs: around people getting high on their own brain chemistry – because it seems obvious to me that people want to change their consciousness – without the deleterious effects of drugs?”.....