Deaths in the U.S. from heroin overdoses doubled between 2010 and 2012 in the 28 states where data was available, according to a study published Friday by the Centers for Disease Control and Prevention.

The sharp increase in heroin-related deaths from 1.0 to 2.1 per 100,000 people held true for both men and women across all age groups and all races except for American Indians and Alaskan natives.

The rise in heroin overdose deaths from 1,779 to 3,665 comes as deaths from prescription painkillers like OxyContin—sometimes referred to as “hillbilly heroin”—have leveled off or fallen across much of the country in recent years, though they remain more common than heroin overdoses. Deaths from drug overdose in general have been increasing in the U.S. over the past 20 years.

Experts believe the increase in heroin deaths may be linked to a crackdown on abuse of prescription “opioid” painkillers, making the synthetic drugs more expensive at a time when heroin is flooding the market.

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