(CNN) - New York doctors who received payments from pharmaceutical companies that make opioids were more likely to prescribe the drugs to their patients, according to a new report from the New York State Health Foundation.
The findings -- similar to the results of a national investigation done by CNN in March -- increase concern that money from pharmaceutical companies influences doctors' prescribing habits.
"It's a systemic issue that is troubling and needs to be addressed," said David Sandman, chief executive of the New York State Health Foundation, which issued the report. "It's financial relationships that really raise eyebrows."
Doctors' groups have denied that payments from pharmaceutical companies -- which are legal -- influence their prescribing habits.
The study found that between 2013 and 2015, about 3,400 New York doctors received more than $3.5 million in payments related to opioids from pharmaceutical companies.
Those payments from pharmaceutical companies to doctors include fees for speaking and consulting, as well as money for travel and meals. Pharmaceutical companies are required to report these payments to the federal government.
About nine out of 10 New York doctors who prescribed opioids received no opioid-related payments from pharmaceutical companies.
The doctors who did get payments were particularly high opioid prescribers.
The study authors determined that on average, for every $1 a New York doctor received in opioid-related payments from pharmaceutical companies, the doctor prescribed an additional $10 or more in opioids to Medicare patients.
The study found that 33 New York doctors were particularly high earners, receiving more than $10,000 in opioid-related payments from pharmaceutical companies from August of 2013 through December of 2015. Those high earners were also high prescribers: On average, they wrote $1.2 million in opioid prescriptions during that time period.
In contrast, those who didn't make much money from pharmaceutical companies wrote relatively fewer prescriptions. There were 529 doctors who received less than $20 from opioid manufacturers during the time period, and they prescribed on average only about $34,000 worth of the drugs, according to the report.
The CNN investigation in March reported that in 2014 and 2015, more than 200,000 doctors nationwide who wrote opioid prescriptions also received payments from companies making opioids. The opioid manufacturers' payments exceeded six-figure sums for hundreds of doctors, and thousands nationwide received more than $25,000.
CNN's data analysis, done in collaboration with researchers at Harvard University, determined the quantity of opioid prescriptions by doctors and the amount of money they received were closely linked, with the likelihood of getting paid more steadily rising for higher prescribers.
"Our work very much supports and confirms the work that CNN did," the New York State Health Foundation's Sandman said. "We also tried to branch off in some new directions as well in our report."
The New York report looked at the timing of payments and prescribing. It found that a doctor who received opioid-related payments had larger increases in his or her opioid prescribing the next year compared to doctors who had not received such payments.
"You start to see a big spike," Sandman said.
He added that given the severity of the opioid crisis, it's reasonable to consider banning such payments by pharmaceutical companies.
Doctors' groups, however, have pointed out that reports like this one don't find a definite causal relationship between payments and prescriptions.
Dr. Thomas Madejski, president of the Medical Society of the State of New York, said that doctors who put profit above patients should be punished.
"Any physician that chooses to prescribe any medication for reasons other than patient need faces threat of significant sanction ... as well as potentially criminal and civil penalties," Madejski said in a statement to CNN.
He went on to question the validity of the New York State Health Foundation report.
"To make an assertion that New York physicians are prescribing opioids because of payments from drug companies is completely at odds with recent statistics showing a significant decrease in opioid prescribing in New York," Madejski said.
But the authors of the report say Madejski's analysis is wrong.
While opioid prescribing has been decreasing, doctors are still receiving payments from pharmaceutical companies, and when doctors get those payments, their opioid prescribing increases, said Mark Zezza, director of policy and research for the New York State Health Foundation.
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