Beyond that, the researchers say, doctors here have long prescribed “significantly higher rates” of opioid pain relievers, almost twice the national average. When the government cracked down on legal painkillers, New Hampshire residents were primed to seek out illegal street drugs.

“This is a kind of perfect storm,” says Lisa A. Marsch, a professor of psychiatry and health policy at Dartmouth’s Geisel School of Medicine and the study’s principal investigator.

“We have highly available, highly potent opioids in New Hampshire,” she says. “And highly limited resources to reduce the risk.”

The researchers noted other factors, too:

• A shortage of workers in addiction and recovery. Northeast states have an average of 15.5 doctors per 100,000 residents who can prescribe Suboxone and other medication-assisted treatments; New Hampshire has seven.

• No needle exchanges, which can reduce the transmission of diseases like hepatitis C and save health care costs. New Hampshire finally legalized needle exchanges in June, long after many other states had done so, but did not fund them. Dartmouth medical students, using donations and grants, opened the first needle exchange last summer in a Claremont, N.H., soup kitchen, but it was shut down in October because it was too close to a school.

• “Live Free or Die.” The researchers said the New Hampshire ethos of “self-sufficiency and individualism” could inhibit some residents from seeking help. And for some, they said, the state’s “Live Free or Die” motto might justify risky behaviors. The state does not require drivers to wear seatbelts. It allows motorcyclists to ride without helmets. And state liquor stores are right on the major highways.