The U.S. FDA has granted a priority review for ixazomib, a drug for treatment of patients with multiple myeloma. Reuters

On every health concern from AIDS to vaccines, nearly half of American adults believe the federal government, corporations or a combination thereof are withholding valuable information from the public. A new survey finds that 49 percent of Americans believe in least one medical conspiracy theory and buy into the notion that some health officials aim at keeping the U.S. population unhealthy.

The study, published in the journal JAMA Internal Medicine, found that “high conspiracists” – those who believe in multiple government or corporate coverups – are more likely to alter their health behaviors based on their beliefs. For example, the survey found that high conspiracists use alternative medicines, buy farmstand or organic food and use herbal supplements at a higher rate than those who said they only believe in one conspiracy.

The study looked specifically at the extent of American support for six popular medical conspiracy theories, including that health officials push vaccines on children even though doctors “know” they cause psychological disorders like autism and that the U.S. Central Intelligence Agency created the AIDS virus to deliberately exterminate black Americans.

“These narratives seem like very compelling explanations for complicated situations,” Eric Oliver, a lead author of the study, told Live Science. “If you hear a noise in the bush, it’s much more adaptive to believe that there’s a predator there than not.”

Researchers polled 1,351 adults about their conspiracy beliefs. They found that 49 percent of them believe at least one of the theories and that 18 percent believe at least three.

Oliver said that because medicine is complicate and “cognitively challenging,” rather than accept some of the uncertainty, people choose to see smokescreens.

"Although it is common to disparage adherents of conspiracy theories as a delusional fringe of paranoid cranks, our data suggest that medical conspiracy theories are widely known, broadly endorsed and highly predictive of many common health behaviors," the researchers note in their study.

Here are the six popular medical conspiracies polled in the survey:

The Food and Drug Administration is intentionally withholding natural cures from the public because of pressure by drug companies. The survey revealed that 37 percent of participants buy into the idea that the federal government is keeping “hidden cures” for several diseases, including cancer, locked away. The belief is that drug companies are profiting by treating cancer patients and that the government is therefore safeguarding the flow of cash.

Health officials push vaccines on children even though doctors “know” they cause psychological disorders like autism. Twenty percent of respondents in the study said they agree with this theory, despite studies that prove otherwise. The theory is fueled by celebrities like Jenny McCarthy and Kristin Cavallari, who have publicly stated they won’t vaccinate their kids.

The CIA created the AIDS virus to deliberately infect black Americans. About one in 10 Americans believes this one, according to researchers. They say AIDS was part of the Pentagon’s bioweapons program and that the virus was created by splicing together several viruses from African and Latin America.

Fluoride in our drinking water is just a coverup for chemical companies dumping their toxins into our water supply. Twelve percent said they believe fluoride in our water is just toxic waste.

The government knows cell phones cause cancer but refuse to stop it. One in five Americans agree with this statement. This conspiracy theory says that large corporations won’t let the government reveal the dangers of cell phone use for reasons similar to why they supposedly withhold certain cures.

GMO food is part of a secret program to shrink the population. The study noted that 12 percent of conspiracy theorists say this is true. The program is called Agenda 21, which actually is a real thing, but it’s not a means for world domination.