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Call it the Jolie Effect.

In 2013, Angelina Jolie published an op-ed in the New York Times explaining her choice to undergo a preventive double mastectomy after testing positive for genetic mutations in the BRCA1 gene, meaning she was at a significantly high risk of developing breast and ovarian cancer. Jolie encouraged other women to undergo the same testing, which costs more than $3,000.

Now, Harvard researchers have concluded that Americans have spent about $14 million on unnecessary BRCA testing since Jolie's op-ed went viral. A paper, published in BMJ, analyzed rates of BRCA testing and mastectomy before and after the op-ed was published of almost 10 million insured women.

Because harmful mutations in the BRCA1 and BRCA2 genes are relatively rare, experts recommend only undergoing the testing if you have an individual or family history of the mutations. Jolie's article explained that she was at an increased risk, but, as the researchers found, perhaps did not make clear enough to readers these recommendations.

"Daily BRCA test rates increased immediately and sharply after publication of the editorial," the researchers found, rising from 0.71 tests per 100,000 women in the 15 business days before to 1.13 tests in the 15 business days after. However, there was no significant increase in mastectomies for the same group of women in subsequent months, indicating that the BRCA testing did not lead more women to discover genetic mutations (or that they did not want to undergo a mastectomy).

The researchers estimate the increased testing in the 15 days after Jolie's article was published translated into about $13.5 million in health care expenditures.

"Celebrity announcements in the social media age can raise awareness and use of preventive care by a large and broad audience, although their ability to target subpopulations of interest may be limited," the paper concludes.

A separate study, conducted by researchers at the University of Maryland, found that Jolie's op-ed, while well-intentioned, did not improve the average reader's understanding of the risk. "While three of four Americans were aware of Angelina Jolie's double mastectomy, fewer than 10 percent of respondents had the information necessary to accurately interpret Ms. Jolie's risk of developing cancer relative to a woman unaffected by the BRCA gene mutation," the researchers wrote.

As Vox's Julia Belluz writes, celebrity endorsements often lead to misunderstanding. This isn't to suggest that Jolie's was not an admirable cause, but to encourage everyone to research serious health issues beyond a well-written op-ed.