This map shows how the opioid epidemic varies in different parts of the US

A new study suggests that the US opioid epidemic is actually several different epidemics occurring at the same time — and finds the epidemic varies in different parts of Massachusetts, too.

The study, published in the journal Rural Sociology, looked at opioid deaths across the United States, county by county, and found regional differences in the types of opioids that caused the most overdose deaths.

“Our results show that it’s more helpful to think of the problem as several epidemics occurring at the same time rather than just one,” David Peters, a sociology professor at Iowa State University who was one of the coauthors of the study, said in a statement from the university.

“And they occur in different regions of the country,” he said, ”so there’s no single policy response that’s going to address all of these epidemics. There needs to be multiple sets of policies to address these distinct challenges.”

The study found prescription drug epidemics, heroin epidemics, and synthetic/prescription epidemics. In the latter type of epidemic, the problem is synthetic opioids like fentanyl being mixed with prescription drugs and then pressed into counterfeit pills, or sold in powder form that is passed off as heroin.

The study also found some regions had an opioid syndemic, where multiple types of deadly opioids were running rampant. In the syndemic counties, “people are dying of every possible opioid and every possible combination of opioids,” Peters said in an interview.

Peters said the study, which used data from the Centers for Disease Control and Prevention, found that Central and Western Massachusetts were experiencing an opioid syndemic. Franklin and Hampshire counties were exceptions; heroin was found to be the main problem there. But the researcher said the most recent data for the study came from 2016, and he suspected that if 2018 data were used, Franklin and Hampshire would join the syndemic.

The story was different for Eastern Massachusetts, which was experiencing an epidemic because of synthetics mixed with prescription drugs.

“The main point is that synthetics/fentanyl is the main ingredient giving these street mixtures their potency, and dealers also mix in [prescription drugs] or heroin (sometimes cocaine) depending on availability,” Peters said in an e-mail.

One county in the state was rated to have low opioid overdose mortality: the island county of Nantucket.

Two-thirds of all overdose deaths nationwide involve opioids, with close to 360,000 people killed since 1999, the study said.

The opioid crisis has “rapidly evolved from a prescription problem to one involving a myriad of opioid substances. In this sense, the crisis is like the multiple-headed Hydra of ancient Greek mythology, involving heroin, prescription, and synthetic opioids. As communities sever one head of the opioid problem, a new drug appears to take its place,” the study said.

The study recommended expanded drug addiction and treatment services; programs to try to reduce the demands for drugs; and programs to help communities that have been “left behind“ create economic security, social order, and physical order.

Here’s what the study found for the different types of opioid epidemics affecting Massachusetts counties:

Barnstable County — Synthetic+Prescription

Berkshire County — Opioid Syndemic

Bristol County — Synthetic+Prescription

Dukes County — Prescription

Essex County — Synthetic+Prescription

Franklin County — High Heroin

Hampden County — Opioid Syndemic

Hampshire County — High Heroin

Middlesex County — Synthetic+Prescription

Nantucket County — Low Opioid Overdose Mortality

Norfolk County — Synthetic+Prescription

Plymouth County — Synthetic+Prescription

Suffolk County — Synthetic+Prescription

Worcester County — Opioid Syndemic

Martin Finucane can be reached at martin.finucane@globe.com.