“If I have it, there’s nothing I or anyone else can do at this point,” Walker said. “There is no cure for it or anything right now that even controls the symptoms really well. Knowing isn’t going to prevent me from having it. I either have it or I don’t. At this point in life, I don’t need to know.”

By avoiding the medical test, Walker is part of a phenomenon referred to as information aversion, or the “ostrich effect” (which comes from the myth that ostriches, when in danger, bury their heads in the sand). It’s often used to describe people avoiding risky financial situations, like investors who check their portfolios less when the market’s bad, who were the subject of a 2009 study. But the term also applies to people avoiding medical tests.

Postponing getting a medical test could lead to a late diagnosis or unknowingly spreading a contagious disease. But living in uncertainty can also cause anxiety and affect how people choose to live their lives.

There are many reasons people might put off going to the doctor, according to Dr. Ghadeer Okayli, a psychiatrist in Austin, Texas who specializes in anxiety, depression, and mental illness. It could be that someone has social anxiety, and he’s afraid of being judged by doctors. Sometimes it could be caused by a panic disorder, if patients fear exhibiting physical symptoms like sweating or trembling if they go to a doctor. Someone might not have the time or money to see a physician. Or it could just be pure apathy. But for a large number of Okayli’s patients who avoid medical tests, they’re scared that a test will reveal a disease they have. It’s a form of denial, according to Okayli—they assure themselves they’re fine while worrying, deep down, that they’re not.

“Some people avoid tests because they don’t want to deal with the stress right now and just want to enjoy life,” said Okayli, who has worked with these kinds of patients for more than 15 years.

“Unnecessary stress or anxiety” was the top reason many college students gave for opting out of being tested for herpes in a study published earlier this year and led by Josh Tasoff, an economist at Claremont Graduate University, and Ananda Ganguly, an associate professor of accounting at Claremont McKenna College. Five percent of students in the study refused to take an HSV-1 test, for oral herpes (which causes cold sores), and 15 percent refused to take an HSV-2 test, for genital herpes (which causes genital sores), even though they were told their blood would be drawn regardless and the test results would be released confidentially. The students even chose to pay $10 to avoid this otherwise free test.

No one wants to find out they have herpes, a stigmatized disease that’s often the target of jokes and slut-shaming, but there are consequences to not knowing.

“In the traditional model of economics, the only reasons people want information is because it can help them make better decisions,” Tasoff said. “With HSV (herpes simplex virus), it does help one make somewhat better decisions. You can’t use the information to cure yourself, since no cure exists, but there are still actions you could take to improve your life, should an outbreak occur, to know how to deal with it and prevent others from getting it.”