(CNN) -- A new report about the sex habits of young adults has turned up a worrisome discrepancy.
Researchers tested 14,000 young men and women for the sexually transmitted diseases chlamydia, gonorrhea and trichomoniasis. Among those who had an STD, 10% claimed in a large national survey that they abstained from sex.
"They were self-reporting that they hadn't had sex in the past 12 months, but they were testing positive for an STD," says Jessica Sales, a co-author of the report published Monday in the medical journal Pediatrics. Approximately half reported no history of sexual intercourse at all.
Sales, of the Department of Behavioral Sciences and Health Education at Emory University, acknowledges that some of the survey participants were "being dishonest" about their sex lives. Lying, however, doesn't fully explain the discrepancy. Some young adults may have simply forgotten that they had sex or acquired the infections before the 12-month period they were asked about in the survey.
"There is also the potential they could have actually had other forms of sexual behavior that could have led to them testing positive for an STD," Sales says. "We think it's probably a combination of all these things."
The discrepancies occurred equally among all young adults. There were no differences by gender, race, age or ethnicity.
Regardless of the reasons, the study authors say their findings highlight some of the ambiguity contained in self-reports of young people's sex lives. They advise health professionals to exercise caution when using such reports to examine STD risk.
"Young people receiving clinical services, whether their sexual history indicates they are recently sexual active or not, should be tested for prevalent STDs," the authors note in their report.
"If pediatricians and adolescent medicine physicians do not test all young people, there are likely a substantial number of missed cases of STDs that will go undiagnosed, untreated, and spread to future sex partners."