12/17/2013 06:50 EST | Updated 02/16/2014 05:59 EST

Why we listen to health-care advice from celebrities

We take cues from celebrities on what to wear, what to watch and how to spend our money. But we’re also listening to their health advice, and that could be dangerous.

New research from McMaster University suggests that common folk are hard-wired to take medical advice from celebrities. And given that some of them think oral sex is linked to throat cancer, or that vitamins cure post-partum depression, we might be putting our own lives at risk, suggests new research published Wednesday in the British Medical Journal.

“It makes sense to follow a model’s advice on fashion or an actor’s advice on presentation, or a former president’s advice on foreign policy,” says Steven Hoffman, assistant professor of clinical epidemiology and biostatistics in the Michael G. DeGroote school of medicine at McMaster.

“But it doesn’t make sense to follow Jenny McCarthy’s advice on vaccines.”

So why do we listen? Human beings are wired to emulate people they admire, says Hoffman, who examined studies dating back to 1806. It’s called the “self-esteem motive” — following advice from celebrities who match how we want to perceive ourselves by purchasing products they endorse.

Halo effect

The tendency extends to health. Celebrity status causes a “halo effect” that gives celebrities “a cloak of generalized trustworthiness which extends well beyond their industry of expertise,” Hoffman’s article says. By wanting to follow in celebrities’ footsteps, their admirers also follow their health advice.

Sometimes this has positive results, Hoffman says. Michael J. Fox, for example, has raised more than $350 million for Parkinson’s research, and Elton John has raised $300 million for HIV/AIDS research.

But Hoffmann notes there are other examples: British broadcaster Michael Parkinson says that “if you can pee against a wall from two feet,” you’re unlikely to have prostate cancer; and McCarthy has falsely linked the use of vaccines to autism.

People listen, too. In the month after Katie Couric broadcast her colonoscopy, Hoffman says, colorectal screening increased by 21 per cent.

Productive partnerships

In understanding the influence of celebrities, Hoffman says, health organizations could partner with celebrities in productive ways. Also, when patients are influenced by celebrity health claims, health professionals can take advantage of the moment to educate.

“People need to always be thinking about what evidence underpins whatever health claim we hear,” Hoffman says. “Is it supported by studies on humans or animals? Was it a trial or based on one person’s experience?

“We have to think about who we trust for health advice and why they might be trusting them. If you have questions, you should go to a doctor who knows you and your family most.”

Laurie Mawlam, executive director of Autism Canada, says McCarthy "creates "conversation and opens doors for investigation."

"I believe people listen to celebrities only as an avenue for further investigation," she said.

Hoffman's team searched electronic databases to analyze economic, marketing, psychology and sociology studies. His work is supported by the Canadian Institutes of Health Research and the Trudeau Foundation.