Physician influence can be bought for as little as a $20 meal, UCSF researchers have found. A study published Monday in JAMA Internal Medicine ... found that doctors who received just one meal averaging $20 were up to twice as likely to prescribe brand-name drugs being promoted than doctors who did not receive any free food. Gifts from pharmaceutical companies to doctors ... have come under scrutiny in recent years for concerns that the money spent by drugmakers directly influences what physicians write on their prescriptions pads. Some doctors deny they're influenced by money, but a growing number of studies show that financial ties can affect their professional behavior. The UCSF researchers looked at ... the routine briefings many doctors and their staff receive from drug reps during lunches in their offices. The study found that the effect increased as doctors got more meals. Those who received multiple meals were up to three times as likely to prescribe the promoted brand-name drug. Higher-cost meals were associated with greater influence. Doctors who received four or more meals to promote Allergan's Bystolic to treat hypertension prescribed the drug at 5.4 times the rate of physicians who received no meals. For Pfizer's depression drug Pristiq, that rate was 3.4 times higher. UCSF researchers said that their studies show the buying power of drug makers decreases the use of cheaper, generic drugs and raises costs for patients as well as the health care system.