The U.S. opioid crisis is beginning to hurt population growth, according to a new report from the National Center of Health Statistics released on Thursday.

Drug overdose deaths more than tripled from 1999 to 2016, increasing from 6.1% to nearly 20%. From 2015 to 2016, drug-related deaths jumped 21%, say health researchers at the center, which is housed within the Centers for Disease Control and Prevention (CDC).

Most drug overdose deaths involved opioids (heroin and fentanyl), as well as legally prescribed medications (oxycodone and hydrocodone). In 2016, two-thirds, or 42,000, of 63,632 U.S. drug fatalities involved opioids -- an increase of 28% from 2015.

The corresponding impact on life expectancy, which dropped by two years, to 78.6, is also alarming.

Hardest hit were young adults. Nearly 35%, on average, of every 100,000 adults are dying annually from drug-related deaths, studies say.

In Pennsylvania, one of the hardest-hit states, where drug-related deaths claimed 38 of every 100,000 adults, the U.S. Attorney General's office issued a 19-count indictment against the state's Dr. Raymond Kraynak Thursday. The agency said Kraynak, who operated Keystone Medical Associates with offices in Mt. Carmel and Shamokin, Pa., operated a "pill mill." He was charged with unlawfully distributing and dispensing controlled substances, causing the death of five patients by the unlawful distribution and dispensing of controlled substances, and maintaining two drug-involved premises in his offices.

From January 2016 through July 2017, the agency says Kraynak, an osteopathic doctor, wrote 2.7 million prescriptions for oxycodone, hydrocodone, oxycontin and fentanyl for 2,838 patients. In 2012, the Pennsylvania State Board of Osteopathic Medicine fined him $2,500 after finding that he had prescribed large amounts of "various controlled substances" to seven patients from January 2007 through June 2008. The U.S. Attorney General is seeking to revoke his medical license, close his offices, and hit him with a $500,000 fine.

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This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.