(Reuters) - Coughs usually take longer to clear up than people think, and the gap between how long people expect them 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.