A celebrity endorsement makes people more likely to believe in conspiracy theories, from COVID misinformation to believing JFK's assassination was an inside job

• Celebrities from Richard Belzer to Mark Ruffalo are known for endorsing conspiracy theories.
• Influencers originate a small percentage of new misinformation but have a big impact on its spread.

Mark Ruffalo is a 9/11 truther. Gwyneth Paltrow has endorsed "medical conspiracy theories" through her wellness brand, Goop. Richard Belzer, who played Detective John Munch for 17 years on "Law and Order: SVU," shared the character's belief that the Kennedy assassination was a federal plot — and influenced his fans to think the same.

Far from being the only celebrities who believe in conspiracy theories, sharing misinformation with a large audience can change what viewers purchase, how they think, and even vote.

Belzer, who died Sunday, was of particularly notable influence, according to the Southern Poverty Law Center. His long-term role as a sex crime detective lent him particular credibility to his fans, while he espoused anti-government theories through his multiple books, including one titled "UFOs, JFK, and Elvis: Conspiracies You Don't Have to Be Crazy to Believe."

"He's got a megaphone, no question about that," Robert Thompson, the director of the Bleier Center for Television and Popular Culture at the Newhouse School of Public Communications, Syracuse University told SPLC. "And, as a mainstream actor, he enhances the credibility of someone like Alex Jones by appearing on his shows."

The actor was a friend and fan of conspiracy theorist Alex Jones, appearing on Jones' show and selling his books through the podcast host's website. Jones, who owes the families of Sandy Hook shooting victims $1.5 billion over defamatory conspiracy theories he spread through his show, also sells supplements on his website intended to "create superior male vitality in men," a claim that has not been verified by the FDA.

Dr. Jen Gunter, an OB/GYN and pain medicine physician, told Vox that celebrity wellness brands, such as those touted by Paltrow and Jones, are full of "medical conspiracy theories" — like promoting supplements for made-up ailments, supporting the idea that wearing bras causes cancer, or that the vagina should be steamed clean. Some of the theories are harmless, while others, Gunter said, can lead to infection or other health problems.

An outsized influence

Celebrities, politicians, and other pop culture personalities make up a very small percentage of new misinformation claims, but their influence vastly amplifies its spread and can alter fan behavior, according to research by psychologists and communications researchers.

A 2020 study published by Reuters Institute found — when analyzing false claims related to the COVID-19 pandemic — posts by celebrities and other influencers made up just 20% of the misinformation claims analyzed but accounted for 69% of the total social media engagement.

Psychology & Marketing published a study in 2017 that found that parasocial relationships, in which fans have a false sense of familiarity with media personalities they don't know in real life, make followers more likely to trust the influencers and their brands, and more likely to purchase items celebrities have for sale.

Alex Jones made $165 million over three years selling supplements and other items in the InfoWars store, Rolling Stone reported.

Representatives for Ruffalo, Jones, Paltrow, and Goop did not immediately respond to Insider's requests for comment.

In addition to making their way into health care choices, celebrities toting conspiracy theories may also influence the way people participate in politics. One study by Research and Politics found that voters exposed to conspiracy theories — including debunked claims about widespread election fraud or Russian interference in the election — had less support for democratic institutions.

A New York Times survey found that such conspiratorial beliefs made voters more suspicious of mail-in voting and made voters less likely to trust people who disagree with them politically.

"It feeds into paranoia that makes you give up, since you can't have any effect, and not want to participate in public life, government or politics," Michael Shermer, publisher of Skeptic magazine, told SPLC.

When celebrities like Joe Rogan, Paltrow, and Belzer spread misinformation, they may not be intentionally setting out to impact the way people manage their health or participate in politics — but they know they're sharing their ideas with a receptive audience.

"Because I'm famous I can put this book out and people will read it that wouldn't if my name wasn't on it." Belzer said on Jones' show, adding: "I'm cashing in on my celebrity — for unselfish reasons, I hope."