> Decades of research prove that these programmes curtail disease. Junkies are in fact less prone to sharing needles when they get free ones. That sharply decreases rates of blood-borne illnesses. In 2014 an analysis found that every dollar spent on syringe exchanges spares the government around $7 in HIV-related health-care costs. Needle exchanges opened across America and Europe. For years no one detected the feared rise in substance abuse.

    > That was before the opioid crisis plagued America and economists started looking into the trade-offs. A new study by Analisa Packham published in the Journal of Public Economics uncovers an uncomfortable truth: this particular harm-reduction tool does lots of harm. Ms Packham compares how drug users fared in counties that opened syringe exchanges between 2008 and 2016 with those in counties that did not. Before the clinics opened, upticks in HIV diagnoses or overdoses in one set of counties were mirrored in the other. Once a syringe exchange came to town, outcomes diverged. Rates of HIV fell by 15% in counties with the new programme. But deaths soared. On average syringe-exchange programmes led to a 22% spike in opioid-related mortality. 

    > Simply lowering the risks of getting sick—and the costs of paraphernalia, as Flaco from the Bronx articulated—could also incentivise drug use. Distributing PrEP, an HIV-prevention medication, has been shown to make gay men less inclined to use condoms during sex. So too could harm-reduction tools make addicts use drugs more incautiously. In a study published in 2018 Jennifer Doleac and Anita Mukherjee found that when states legalised naloxone, a medication that reverses overdoses, opioid abuse increased. Though lauded by public-health advocates, naloxone did not save lives as intended. In some regions, fewer addicts died; in others, more did.