WASHINGTON  (CBS DC) – Seems many Americans believe in medical conspiracies, reports Live Science.

Researchers surveyed 1,300 Americans to find out their beliefs about 6 popular theories, including the discredited link between vaccines and autism or that water fluoridation is a cover-up that allows companies to dump dangerous chemicals into the water supply.

Just under half agreed with at least one conspiracy theory. 18 percent agreed with three or more.

The most common belief was the belief that the Food and Drug Administration is “deliberately preventing the public from getting natural cures for cancer and other diseases because of pressure from drug companies.” More than a third of Americans agreed with that statement.

20 percent agreed that “Health officials know that cell phones cause cancer but are doing nothing to stop it because large corporations won’t let them.” About the same percentage that believes vaccines cause autism in children.

Study researcher Eric Oliver, with the University of Chicago, was not surprised by the findings.

“We see that Americans have conspiracy theories about a lot of things, not just about politics, but also about health and medicine as well,” he said.

Oliver added that belief in conspiracy theories is not necessarily a sign of paranoia.

“These narratives seem like very compelling explanations for complicated situations,” Oliver said.

He suggests humans evolved to see patterns in unrelated events.

“If you hear a noise in the bush, it’s much more adaptive to believe that there’s a predator there than not,” he said.

The study is published in the JAMA Internal Medicine.

(TM and © Copyright 2014 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2014 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)