(HealthDay)—U.S. researchers are challenging a leading theory about the nation's heroin epidemic, saying it's not a direct result of the crackdown on opioids. The commentary has been published in the Jan. 14 issue of the New England Journal of Medicine.

Heroin's popularity is soaring—with 914,000 reported users in the United States in 2014, an increase of 145 percent since 2007, according to background notes with the commentary. This has led to a spike in overdose deaths—10,574 in 2014. The commentary authors said that the rise in use began before states launched restrictions on to prevent abuse.

"The prevention efforts don't seem to be pushing people to heroin. We think there are other factors," commentary lead author Wilson Compton, M.D., deputy director of the U.S. National Institute on Drug Abuse, told HealthDay. The common link is that heroin and opioids are in the same class of drugs and have similar effects, he said. "It's the initial exposure to opioids that's pushing them to heroin."

In the past, abusers might have begun with heroin and then turned to the prescription narcotics, Compton said, but now the pattern is reversed. "It's a new pathway, going from pills to heroin," he explained. "There's a reluctance to make that switch [to heroin], but once they begin down that pathway, they discover that heroin is readily available, quite pure, and in many locations cheaper than ."

More information: Full Text

Journal information: New England Journal of Medicine