After the esteemed actor Philip Seymour Hoffman died in February 2014, press coverage of the "heroin epidemic" exploded. Mentions of that phrase in the newspaper and wire service articles cataloged by Nexis rose from 681 in 2013 to 3,222 in 2014, an increase of almost 400 percent. Yet Hoffman—who by his own account used heroin in his early 20s, then abstained for more than two decades before taking up the habit again in 2013—was hardly representative of the upward trend in heroin use that began around 2008, which consisted mainly of people trying the drug for the first time.
Hoffman was typical in at least one respect, however. He died not from a "heroin overdose," as widely reported, but from "mixed drug intoxication" involving cocaine, amphetamine, and benzodiazepines as well as heroin. The combination of heroin and benzodiazepines, a class of drugs that includes Valium and Xanax, presumably was what killed him, since both depress respiration. The dangerous combination of depressants is a very common theme in so-called heroin overdoses, a fact that may help explain why such deaths have climbed dramatically in recent years—more dramatically than you would expect based on the increase in heroin consumption.
According to the National Survey on Drug Use and Health (NSDUH), the number of past-month heroin users rose from 161,000 in 2007 to 289,000 in 2013, an increase of about 80 percent. During the same period, according to the U.S. Centers for Disease Control and Prevention (CDC), the number of "drug-poisoning deaths involving heroin" rose from 3,041 to 8,257, an increase of 172 percent. In other words, the increase in heroin-related deaths was more than twice as big as the increase in past-month use, which means heroin users are more likely to die from drug poisoning than they used to be.
NSDUH misses an unknown number of regular heroin users who either do not respond to the survey, do not respond honestly, or are not part of the household population the sample is designed to reflect. But even if we assume the actual number of past-month users was substantially higher in 2007 and in 2013, it still looks like heroin use has become more dangerous in recent years. The question is why.
As illustrated by the untimely ends of celebrities such as Hoffman, Janis Joplin, John Belushi, Chris Farley, River Phoenix, Heath Ledger, Cory Monteith, and Amy Winehouse, the vast majority of heroin-related deaths involve multiple drugs. According to CDC data presented by Kenneth Anderson, executive director of the HAMS Harm Reduction Network, at last month's International Drug Policy Reform Conference in Arlington, Virginia, two-thirds of heroin deaths in 2013 involved alcohol or other drugs in addition to heroin. Anderson notes that the true share may be higher because death certificates do not necessarily mention other substances in mixed intoxication cases involving heroin. In New York City, which keeps better track of such details than many other jurisdictions, 94 percent of deaths related to heroin or other opioids in 2013 involved multiple drugs.
Although the share of heroin deaths involving other drugs does not seem to have risen since 2007, the frequency of such mixing by heroin users may have, which could help account for the disproportionate increase in deaths. One reason to think the dangerous habit of combining depressants has become more common is the influx of inexperienced heroin users who may be less aware of the hazards such mixtures pose.
A lot of those new heroin users switched from prescription opioids such a hydrocodone and oxycodone after a government crackdown made those drugs more expensive and harder to get. In recent years, as heroin use has been rising, nonmedical use of opioids has been declining. Trends in poisoning deaths involving the two kinds of drugs also have been moving in opposite directions. According to a 2014 JAMA Psychiatry study, younger heroin addicts entering treatment generally started with prescription opioids, a pattern that is much less common among older addicts. More than nine out of 10 addicts who switched from painkillers to heroin reported that they did so because heroin was cheaper and easier to obtain.
Polydrug use may be even more common among prescription opioid users than it is among heroin users. In 2013, according to the CDC's data, 77 percent of deaths related to prescription painkillers involved mixtures, compared to 67 percent of heroin-related deaths. As with heroin, increases in prescription opioid deaths have far exceeded increases in use. The number of opioid-related deaths more than doubled between 2002 and 2011 (from 7,456 to 16,917), even as the number of past-month users remained about the same. Anderson thinks that disparity may be partly due to an increase in the average size or frequency of the doses that opioid users take.
Opioid users who tend to mix drugs face a greater hazard when they switch to heroin because the purity of the latter drug is so unpredictable. While prescription painkillers come in carefully measured doses, heroin potency varies widely over time, across dealers, and from city to city. That variation, a familiar feature of the black market created by prohibition, can be deadly, whether heroin is combined with other drugs or consumed by itself. A heroin user who comes across a batch that's more potent than he expected, whether because it is purer than usual or because it is spiked with something like fentanyl, can easily take too much, especially if he is consuming another depressant at the same time. Novice heroin users accustomed to legally produced drugs sold in standard doses are apt to be less aware of this danger. Another hazard for switchers: The difference between an effective dose and a lethal dose is smaller for heroin than for prescription painkillers.
The war on drugs magnifies the risk of drug poisoning by making heroin purity inconsistent, by pushing prescription opioid users toward heroin, by making friends and acquaintances of users who need medical attention reluctant to call for help, and by discouraging harm reduction measures as simple as cautioning people against mixing heroin or painkillers with other depressants. By design or not, these effects of prohibition presumably discourage drug use by making it more dangerous, but only by sacrificing the lives of those who are undeterred.
This article originally appeared at Forbes.com.