According to a newly released study from the Journal of Substance Abuse Treatment, hard drug users who use both heroin and cocaine have a mortality rate that is 14.3 times higher than the population at large.
For users of cocaine alone, that rate is 5.1 times higher.
The results come from a survey of more than 20,000 drug users in Spain who were admitted into treatment programs over the span of 10 years (1997-2007). The researchers followed up on the participants until 2008, accumulating "a total of 132,824 person-years of follow-up," they wrote—a truly massive amount of data.
The authors suggest this is perhaps the largest sample of drug users ever studied.
Here are some of their grim findings.
- "Heroin use was also the strongest independent predictor of a higher mortality risk among all cocaine users."
- "Other signiﬁcant risk factors were daily cocaine use and having been previously admitted to drug treatment."
- "Not having regular employment and lifetime drug injection were important independent mortality risk factors both among [cocaine-only users] and [cocaine and heroin users]."
Their findings also suggest that cocaine use is slightly more dangerous for women than men, but they are not sure why.
Though the numbers are stark, the researchers do admit that their sample was limited to people who have entered rehab, which could mean the participants in their sample had a more aggressive drug habit than what would be represented in a truly random sample. And also, direct causation can't be inferred from a survey. "This excess mortality cannot automatically be attributed to cocaine or heroin use, because participants and the general population may differ in other factors that were not assessed, such as mental disorders, personality factors, [and] social conditions," they write.
But still, even if it serves as a high boundary of the risks of using drugs, it's a boundary you don't want to approach. After all, who would would want to even double their chance of dying, let alone increasing it 14-fold.