Doctors who receive gifts and payments, such as meals, from pharmaceutical companies write more prescriptions for promoted medications, including ones that are often less appropriate and more expensive for patients, according to a new Cochrane review published on October 9.

The review analyzed 93 studies, mostly from the United States, and used prescribing data from millions of providers. The authors examined three ways pharmaceutical companies engage with physicians: advertising and education, gifts and payments, and free samples. While the review could not determine that pharmaceutical marketing and promotion changed physicians’ prescribing, it found that doctors who accepted gifts and payments from industry showed the strongest correlations with certain prescribing outcomes.

Overall, the authors said, “the more interactions doctors had with pharmaceutical companies, the less appropriate their prescribing was and the more prescriptions they wrote.”

Although the review echoes decades of concerns about pharmaceutical marketing tactics and the conflicts of interest they can create, it also suggests that doctors may not realize the link between industry’s presence and their prescribing decisions.

“Doctors often think that this is trivial and…they ‘can’t be bought for the price of a sandwich,’ but the data shows this is an effective marketing strategy,” lead review author Barbara Mintzes, PhD, professor in evidence-based pharmaceutical policy at The University of Sydney in Sydney, Australia, said in a statement.

Gifts, Meals, and Problematic Prescribing

The clearest findings involved gifts and payments to physicians. Ten studies covering about 2.9 million doctors linked physicians’ interactions with pharma to increased inappropriate prescribing, and 39 studies involving 3.8 million doctors found higher prescription volumes. Another 25 studies assessing the prescribing habits of 2.5 million doctors identified a probable increase in prescription costs.

Industry-sponsored meals had a particularly pronounced effect. Researchers found a “dose-response relationship,” meaning physicians who received more meals prescribed more of the promoted medication.

This relationship held true across various drug categories, including medications for hypertension, depression, and pain management, the researchers said.

Despite those strong correlations, the review authors said they remain “very uncertain” about the impact of free medication samples on physicians’ prescribing decisions. Exposure to pharmaceutical company advertising or education, primarily through visits with sales representatives, had less clear outcomes but was linked to a probable increase in prescription quantity and a possible increase in inappropriate prescribing and medication costs.

Industry’s marketing tactics work because even the smallest gifts trigger a subconscious obligation to reciprocate, said Adriane Fugh-Berman, MD, professor of pharmacology and physiology at Georgetown University Medical Center (GUMC), Washington, D.C.

“No one likes to believe they could be bought off for a meal, book, or pen; it doesn’t fit with their self-perception of themselves as a good, unbiased person,” she told Medscape Medical News.

Fugh-Berman was not involved in the Cochrane review, but she studies physician-industry relationships as the director of PharmedOut, a GUMC initiative that promotes evidence-based prescribing and educates clinicians on the impact of industry marketing.

She said doctors tend to rationalize their prescribing decisions — that they chose a particular drug simply because it’s the best one — rather than recognizing the social psychology dynamics at play.

Doctors’ Evolving Views on Industry

Much of the newer research on these dynamics has been made possible by the federal Open Payments database, which requires pharmaceutical companies and other applicable manufacturers to report payments made to providers. Researchers can link those payment records to population-based prescribing data rather than asking physicians to recall their interactions with industry, Mintzes said.

She said that across 16 studies examining 24 prescribing outcomes, greater exposure to pharmaceutical promotion was associated with greater influence on prescribing.

“This is important because in public health a dose-response effect is seen as a key measure of whether an exposure causes an outcome,” Mintzes added.

Still, the full extent is sometimes difficult to quantify because manufacturers frequently fail to accurately report transaction details. And even with the mounting evidence of industry’s influence, physicians hold somewhat contradictory views on these encounters.

In a longitudinal study published last year in JAMA Health Forum, Eric Campbell, PhD, professor and director of research for the Center for Bioethics and Humanities at the University of Colorado Anschutz School of Medicine in Aurora, and colleagues examined the changes in attitudes toward pharmaceutical marketing among physicians who were medical students and residents when the study began in 2011.

By 2024, participants were more likely to strongly agree that their interactions with industry could threaten the public’s trust in medicine. However, more than three quarters of physicians also strongly agreed that they receive useful information from pharma marketing, up from about 66% in 2011.

Campbell, who was not involved in the Cochrane review, said physicians recognize marketing’s effect on their colleagues but discount it in their own decision-making.

“This is a problem of people believing they cannot be influenced,” he told Medscape Medical News. “It’s akin to saying gravity affects all other people on Earth, but it doesn’t affect me.”

Are Institutional Restrictions the Answer?

The review authors evaluated whether conflict-of-interest policies could counter industry’s reach, finding that they probably improve prescribing appropriateness and may reduce prescribing volume, although evidence on these interventions is limited.

Some institutions already restrict interactions with pharmaceutical companies, including extending those policies to medical students and residents. But Fugh-Berman said policies alone are insufficient.

“There needs to be a hard line between industry and education — no drug reps, samples, industry-sponsored CME [continuing medical education], or patient materials, and teachers in medical schools, residencies, and CME activities should not have relationships with industry,” she said.

Through PharmedOut, she and her colleagues have developed a Grand Rounds presentation, “Why Lunch Matters,” to help physicians consider their susceptibility to industry marketing.

After the presentation’s initial rollout, a study found significant changes in attitudes toward industry, such as an intent to stop meeting with pharmaceutical representatives or attending industry-sponsored meals.

“Our revealing what industry does angered docs in the best way,” said Fugh-Berman. She said the presentation has since been updated and is being delivered again around the country.

State lawmakers have also taken up efforts to rein in industry marketing, with varied success. Massachusetts, Minnesota, and New Jersey are among several states that have enacted restrictions on the type and value of industry gifts to clinicians. Those states and more have adopted laws requiring greater disclosure of industry payments and interactions.

Just this year, Maryland legislators proposed a $50-per-calendar-year limit on gifts from drug and device manufacturers to healthcare professionals. The bill failed to advance out of committee.

Campbell said the Cochrane review adds “methodological rigor” to the already extensive body of research on physician-industry relationships. “This literature is so big and shows that these relationships change doctors’ behaviors,” he said. “I always believed that when the literature got to be substantial enough, this would stop, and it hasn’t. It’s baked into the culture, and it will not change until an external force, like the federal government, puts an end to it.”

Mintzes has acted as an expert witness for Health Canada and Australia’s Therapeutic Goods Administration in two legal challenges to regulatory decisions. Fugh-Berman reported serving as a paid expert witness for plaintiffs in litigation regarding pharmaceutical and medical device marketing practices. Campbell reported no relevant financial disclosures.

Steph Weber is an award-winning freelance journalist specializing in healthcare and law.