Individuals with a history of opioid misuse — but no history of opioid addiction — may help scientists identify genes that protect against opioid-use disorders. To that end, researchers at Washington University School of Medicine in St. Louis are launching a large-scale study for which they plan to recruit 2,000 people who have used opioids recreationally 60 times or fewer and not become dependent on the drugs.
“A person’s genetic makeup plays a major role in whether that person becomes addicted to opioids,” said the study’s senior investigator, Elliot Nelson, MD, a professor of psychiatry. “Opioids are dangerous, habit-forming drugs when used recreationally; however, some individuals are able to use them infrequently without becoming addicted. We believe these individuals are uniquely valuable for identifying protective genetic factors that may provide us with insights for helping people who become addicted to opioids or are at high risk.”
Recent research found that nearly 12 million Americans misused opioids within the year that they were surveyed, and most of these misusers were not addicted. Nelson’s group has received a grant from the National Institute on Drug Abuse (NIDA) of the National Institutes of Health (NIH) to learn about such users.
The opioid epidemic is a public health crisis in the U.S. On average, more than 134 people in the United States die each day from opioid overdoses, according to the U.S. Centers for Disease Control and Prevention. Opioid misuse and addiction — involving prescription pain relievers, heroin or synthetic opioids, such as fentanyl — are estimated to cost the U.S. economy more than $78 billion a year, including health care, lost productivity, addiction treatment and criminal justice expenses.
The current project grew out of a genetic study Nelson and his colleagues had conducted in Australia, in which they compared a large sample of opioid-dependent individuals to a smaller sample of recreational opioid users who were not addicted. The researchers observed a significant association implicating a gene that may have protective effects.
In this new study, they are recruiting recreational opioid misusers who are not dependent on such drugs, with the idea that by studying a larger sample, the researchers will be able to learn more about such individuals and identify additional novel genes that may be involved in protecting people from, or predisposing them to, addiction.
As part of the study, Nelson and his colleagues plan to collect data from 1,000 people of African-American ancestry and another 1,000 of European-American ancestry, all of whom will have used opioids without becoming addicted. Each will provide a blood sample and answer questions about his or her use of opioids in a confidential survey. Current estimates suggest slightly more than 4 percent of people over age 12 have used opioids recreationally during the past 12 months, which totals more than 100,000 users in an area the size of St. Louis.
Nelson and colleagues also have received NIDA funding to conduct another large study also driven by findings from their Australian project. The researchers connected data from that project’s opioid-dependent participants to a national mortality database in Australia.
They were very upset to discover that 11 percent of the study participants — whose ages, on average, were mid-30s during the study — had died during the subsequent six to 11 years, with opioid overdose their most frequent cause of death.
This finding led Nelson and colleagues to seek funding to conduct the first large study seeking to identify genetic factors that contribute to opioid overdose death, analyzing what aspects of their opioid use, and what specific genes, are associated with having died from an overdose.