A new study has found that number of people who are using opioid for nonmedical reasons and overdose deaths in the U.S. rose from 2003 to 2013, even if opioid prescriptions decreased for the same period.

Opioids are often prescribed for pain relief, but the likelihood of abuse and addiction discouraged doctors from including it to their patients' prescriptions, unless it is the only option. Opioid dependence develops when people use the medication regularly for a period of time, and they can suffer from withdrawal symptoms when asked to stop abruptly.

Researchers from the Substance Abuse and Mental Health Services Administration, Rockville, Md. looked at the data of 472,200 people, with ages 18 to 64, to determine the prevalence of nonmedical use and use disorders between 2003 and 2013. They also checked the death causes of those who died during the study period.

The analysis showed that nonmedical opioid prescriptions dropped by 0.5 percent between 2003 and 2013, but opioid misuse increased by 0.3 percent. Deaths due to opioid misuse and overdose also increased by 3.3 percent for every 100,000 in 2013. People use opioids for nonmedical reasons at an average of 200 days in a year, which is also 0.5 percent higher compared to 2003.

"We found a significant decrease in the percentage of nonmedical use of prescription opioids, as well as significant increases in the prevalence of prescription opioid use disorders, high-frequency use, and related mortality among adults aged 18 through 64 years in the United States over the past decade. Furthermore, the increases identified in this study occurred in the context of increasing heroin use and heroin-related overdose deaths in the United States, supporting a need to address nonmedical use of prescription opioid and heroin abuse in a coordinated and comprehensive manner," the authors wrote in a press release.

The researchers recommend the development of new treatments that could help relieve pain and new training programs for doctors so that they can better identify whether someone is using opioid for nonmedical reasons, according to Reuters.

The study was published in the Oct. 13 issue of JAMA.