But the remarkably low rate of opioid misuse by surgery patients was not the primary focus of the study. What researchers really wanted to know is whether the dose and duration of an opioid prescription influences future chances of abuse and addiction.

And here another myth was dispelled.

Researchers found that high doses of opioids after surgery appear to have little impact on misuse rates. Their findings show that how long a patient takes opioids is a more reliable predictor of misuse than how much medication they took. Dosage only emerged as a risk indicator for those who took opioids for extended periods.

"Our results indicate that each additional week of medication use, every refill is an important maker of risk for abuse or dependence," said study co-author Denis Agniel, a statistician at the RAND Corporation and a part-time lecturer in the Department of Biomedical Informatics at Harvard Medical School.

Researchers found that each additional week of opioid use increased the risk for dependence, abuse or overdose by 20 percent. And each refill boosted the risk by 44 percent.

But the risk of misuse still remains small. For those who had a single prescription with no refills – the vast majority of patients -- misuse occurred at a rate of only 145 cases per 100,000 patient years. The rate was still minuscule for those who refilled a prescription -- 293 cases per 100,000 patients years.

And for patients who took high doses for short periods -- two weeks or less -- the risk of misuse was no greater than those who took an average dose.

Agniel and his colleagues say their research indicates that opioids -- even at high doses -- can be safely prescribed to patients with post-surgical pain.

“These findings suggest a more nuanced understanding of the relationship between duration and dosage with a focus on early appropriate treatment of pain (including higher doses) for a limited time,” researchers concluded.

“Such findings suggest that optimal post-operative prescribing, which maximizes analgesia and minimizes the risk of misuse, may be achieved with moderate to high opioid dosages at shorter durations, a combination that merits further investigation in population-based and clinical studies.”

Anti-opioid activists and government regulators have long made sensational claims that even just a few painkillers can lead to addiction and death.

“The bottom line here is that prescription opiates are as addictive as heroin. They’re dangerous drugs,” former CDC Director Thomas Frieden told the Washington Post in 2016. “You take a few pills, you can be addicted for life. You take a few too many and you can die.”

The Harvard Medical School study was not the first to find that long term opioid use after surgery is rare. A 2016 Canadian study found that less than one percent of older adults were still taking opioid medication a year after major elective surgery.

Many patients are dissatisfied with the quality of their pain care in hospitals. In a survey of over 1,200 patients by PNN and the International Pain Foundation, 60 percent said their pain was not adequately controlled in a hospital after surgery or treatment. And over half rated the quality of their hospital pain care as either poor or very poor.