Over a year ago, celebrity Angelina Jolie decided to undergo a preventive double mastectomy, which is the surgical removal of both breasts in order to decrease breast cancer risk.

After having the operation, Jolie publicly announced it and encouraged other women to get tested themselves. The number of women getting genetic breast cancer tests increased significantly after Jolie’s experience. Now, research published in the journal Breast Cancer Research has found that her announcement led to a doubling of the number of women getting tested; researchers have dubbed this phenomenon the “Angelina Jolie effect.”

Last year, Jolie discovered she carried the BRCA1 gene, which may increase a woman’s risk for breast cancer, and decided that it was safer to undergo a double mastectomy. “My doctors estimated that I had an 87 percent risk of breast cancer and a 50 percent risk of ovarian cancer,” she wrote in a May 2013 New York Times op-ed article. “Once I knew that this was my reality, I decided to be proactive and to minimize the risk as much as I could.”

In the study, researchers examined 21 clinics and regional genetic centers, finding that the number of testing referrals increased from 1,981 in 2012 to 4,847 in 2013. “Angelina Jolie … is likely to have had a bigger impact than other celebrity announcements, possibly due to her image as a glamorous and strong woman,” said Gareth Evans, a researcher with the charity Genesis Breast Cancer Prevention, in a statement. “This may have lessened patients’ fears about a loss of sexual identity post-preventive surgery and encouraged those who had not previously engaged with health services to consider genetic testing.”

The BRCA1 and BRCA2 genes produce tumor suppressor proteins, which help repair damaged DNA. If the genes are mutated, they will not be able to work to correct damaged DNA; cells are thus more likely to develop other issues that can cause cancer. Very specific inherited mutations in BRCA1 and BRCA2 increase the risk of female breast and ovarian cancers.

“I am writing about it now because I hope that other women can benefit from my experience,” Jolie wrote in her op-ed piece. “Cancer is still a word that strikes fear into people’s hearts, producing a deep sense of powerlessness. But today it is possible to find out through a blood test whether you are highly susceptible to breast and ovarian cancer, and then take action.”