“This same aversion to intravenous drug use—to shooting up—had also served as a natural cap on the size of the market for heroin in the United States. But when somebody who is already addicted to opioids starts to feel the first pangs of withdrawal, a lifetime’s worth of inhibitions can be swiftly cast aside. This is the logic of addiction. Maybe needles make you queasy. But if your body is acting as if you might die if you don’t get a hit, you’ll start doing all sorts of things you might have sworn, in the past, that you would never do.”