While opioid addiction and abuse continues to figure as the most serious public health emergency in the United States, academic research is increasingly able to identify some of its causes.

Now, a new study in the American Sociological Review, “Does intra-household contagion cause an increase in prescription opioid use?”, carefully traces the contagion of opioid use among families. In an analysis of hundreds of millions of medical claims and almost 14 million prescriptions in one state between 2010 and 2015, sociologists Mathijs de Vaan and Toby Stuart of the Haas School of Business at University of California, Berkeley, demonstrate that household exposure to opioid use increases patient demand for prescriptions among family members. The study’s conclusions should impact how and when opioids are prescribed, particularly when driven by patient demand.

Untying the knot of opioid addiction is challenging. In this study, the authors began with the understanding that genotypic similarities, assortative matching in partner selection (the tendency for “like marrying like”), and the clustering of certain health conditions within households might explain why members of the same household exhibit similar patterns of opioid use. Controlling for those factors as well as restricting the analysis to family behavior only after the first family member received an opioid prescription, the authors still found a significant impact from the family household in accelerating opioid consumption to unprecedented levels.

Moreover, the family connection is not a function of family members being treated by the same physician. De Vaan and Stuart winnowed the data to patients who received their opioid prescription from physicians working in emergency rooms, where the doctor-patient match is random, where physicians prescribe opioids at different rates, and where a patient’s family members cannot request to see a doctor who has already prescribed opioids to their relative. The study also demonstrates that physicians respond to their “market”: although there are many factors influencing which doctors prescribe opioids most often, the findings suggest that the spread of prescription behavior in physician networks may be driven by shifts in demand that propagate through the network of patients they share.

The study authors conclude with some practical policy recommendations. If receiving an opioid prescription puts the patient’s family members at risk for requesting opioid prescriptions themselves, providing incentives to patients to return unused opioids—as is encouraged on National Prescription Drug Take Back Day—would have a protective effect. And, expanding the Prescription Drug Monitoring Program (the database that records all prescriptions in some states) to allow physician access to both individual and family members’ medical history may help physicians decide if an opioid prescription demand may be the result of family consanguinity.

“Using empirical strategies, we found a sizable contagion effect,” the authors wrote. “In light of the research design choices we made to estimate the cleanest possible treatment effect, it is probable that the intra-family social contagion effect we present is an underestimate of the true incidence of within-household contagion of opioid use.”

“We believe intra-household exposure or access to opioids, even when exposure is randomly generated by the matching process between patients and physicians in the emergency department, causes at-risk family members to become more aware of and knowledgeable about the efficacy of opioids. When that occurs, at-risk family members are likely to request and possibly even insist on an opioid prescription when they subsequently visit a physician for a pain-related condition.”

Read the full article at www.asanet.org/research-and-publications/journals/american-sociological-review.