One in four drug overdoses in the U.S. in 2015 were related to heroin, according to new numbers released Friday by the Centers for Disease Control and Prevention. Not only was 2015 the first year that the number of overdose deaths in the U.S. exceeded 50,000, but deaths from opiods increased from 57 percent to 73 percent in only five years. “Starting in 2011, overdoses involving heroin has really skyrocketed,” Andrew Kolodny, of Brandeis University's Opioid Policy Research Center, said, “There's a really good chance the increase involving heroin has to be involved with fentanyl.” The CDC study also found a significant increase in the number of deaths related to synthetic opiods, such as fetanyl, the drug linked to Prince's death this past year. Researchers contend that prescription drug use is being replaced by heroin use because of the cost and crackdown on illegal use of prescription opiods.