When doctors were invited out to just one dinner with only one opioid vendor, they were more likely to prescribe opioids; a new study revealed this week. According to Forbes, the average salary of a medical doctor in the United States in 2014 was $189,000. However, it appears that a “dinner date” was simple enough to influence doctors to prescribe a larger volume of opioids to patients.

Researchers exploring the links between pharmaceutical marketing and doctors’ opioid prescribing habits analyzed data on free meals and opioid prescription numbers for their new report. Their findings confirmed something awful: the more meals physicians ate with pharma reps in 2014, the higher the number of opioids they ended up prescribing in 2015. This was in a year where a record 47,055 people died from overdoses, according to the CDC.

How Much Did The Doctors Increase Prescriptions?

The correlation between physicians’ prescribing habits and dinner dates were so significant that researchers were able to crunch the numbers even further into an actual equation. Each meal shared between physicians and pharma reps was associated with an increase of 0.7% in opioid prescriptions.

In 2014, doctors accepted more meal perks from pharma reps than any other form of promotion. 97,000 physicians let these companies pay for breakfast, lunch or dinners. Pharmaceutical manufacturers spent a total of $1.81 million on these marketing meals for doctors, with a high cost to susceptible patients.

The report also dissected speaker fees, travel, consulting fees and education. The spending in these areas totaled $9.07 million in 2014. Insys Therapeutics, the maker of Subsys fentanyl spray, spent the most in total nonresearch payments to doctors. Their efforts in these areas totaled $4.54 million, followed by Teva at $869,000, and Johnson & Johnson’s Janssen unit at $854,251.

These findings come as Insys Pharma is under federal investigation for its marketing practices, and Purdue Pharma, the maker of Oxycontin, has been the subject of dozens of state and local-level lawsuits. Purdue promised late last year to stop actively marketing Oxycontin to doctors but did not promise the same for any future variations of opioids.