Coughs usually take longer to clear up than people think, and the gap between how long people expect then to last and how long it actually takes may drive some patients to the doctor for antibiotics that won’t help, according to a U.S. study.

Researchers in the U.S. state of Georgia wrote in the Annals of Family Medicine that survey respondents tended to expect their cough to be gone in about a week, but a review of cough studies shows the hacking takes about three weeks to clear up.

The team, led by Mark Ebell from the University of Georgia in Athens, said they were concerned that patients’ unrealistic expectations could lead them to ask doctors for antibiotics that won’t speed their recovery, but will fuel drug resistance, cost money and increase the risk of side effects.

“Efforts to reduce inappropriate antibiotic use should target this discrepancy,” the authors wrote, referring to unrealistic patient expectations.

“We’re not trying to discourage people from getting care if they feel they need it, but at the same time we want to give them the confidence to give themselves care in situations when it’s appropriate,” said Ebell.

For the study, Ebell and his colleagues did a telephone survey of 493 adults in George about how long they’d expect a cough to last based on a hypothetical situation: if they had a 100.5 degree Fahrenheit (38 degree Celsius) fever and were bringing up yellow mucous.

Overall, people said they’d expect the cough to take between 7 and 9 days to clear up.

The team then reviewed 19 previous studies on severe coughs that recorded how long the condition actually lasted. In those studies, it took a cough – on average – 17.8 days to subside.

“I think it is important to understand that if you do get a cough you’re probably going to be coughing for about three weeks,” said Jeffrey Linder, who was not involved in the study but has done similar research.