The study’s authors caution that the findings, off of Medicare Part D prescription drug data, don’t suggest a direct link between payments and doctors choosing to prescribe drugs from the specific companies making those payments. But they did find a clear correlation between average rates of overall brand-name prescribing and receiving industry money.

That’s ultimately a plus for pharmaceutical companies’ revenue, and the trend consistently grows stronger the more industry money a doctor receives. For instance, internal medicine specialists who nabbed more than $5,000 had a 30.1% brand-name prescription rate in 2014, as opposed to the 19.8% rate for doctors who received nothing.

The correlation held true across major specialties such as family medicine, ophthalmology, and cardiovascular disease.

Medical device and pharmaceutical firms can make payments to doctors through a number of avenues for a variety of reasons. For instance, they can cover physicians’ meal or business travel costs, or pay them to be speakers at certified Continuing Medical Education events.

These payments must now be made public under an Obamacare provision called the Physician Payments Sunshine Act and are listed on the federal government’s Open Payments website.

In 2014, doctors received a total of $6.5 billion from drug and device companies. Earlier this week, the pharmacy benefits giant Express Scripts (ESRX) reported that the average prices of brand name drugs have doubled since 2011, contributing to a massive surge in Medicare drug spending.