People who visit the emergency room at least four times in one year are at much greater risk of dying from a prescription drug overdose, compared with those who visit the ER once a year or not at all, a new study finds.

Patients with four or more ER visits in the past year were 48 times more likely to die from a prescription drug overdose. Those who visited three times in one year were 17 times more likely, compared with those who visited once or not at all.

The study included data from more than 5,400 patients who visited ERs in New York State between 2006 and 2010, according to HealthDay.

Patients at highest risk of death from a prescription drug overdose were those with substance use disorders or other psychiatric disorders; men; whites; and those ages 35 to 54.

“While ‘doctor-shopping’—the practice of visiting multiple health care providers to obtain controlled substances—has been shown to be associated with prescription drug overdose in many studies, our investigation demonstrates that the frequency of emergency department visits in the past year is a strong predictor of subsequent death from prescription drug overdose,” researcher Joanne Brady of the Columbia University Mailman School of Public Health said in a news release.

The study is published in the Annals of Epidemiology.

The researchers say ER visits can be an important window of opportunity for identifying patients at increased risk of prescription drug overdose, and for implementing evidence-based intervention programs. These include giving patients drug treatment referrals, and providing patients and their families with take-home naloxone, an opioid overdose antidote.