Kim Painter

Special for USA TODAY

Nearly half of American adults believe the federal government, corporations or both are involved in at least one conspiracy to cover up health information, a new survey finds.

Conspiracy theories on everything from cancer cures to cellphones to vaccines are well known and accepted by sizable segments of the population, according to a research letter published this week in JAMA Internal Medicine.

The findings reflect "a very low level of trust" in government and business, especially in pharmaceutical companies, says study co-author Eric Oliver, a professor of political science at the University of Chicago. They also reflect a human tendency to explain the unknown as the work of "malevolent forces," he says.

The online survey of 1,351 adults found:

• 37% agree the Food and Drug Administration is keeping "natural cures for cancer and other diseases" away from the public because of "pressure from drug companies."

• 20% believe health officials are hiding evidence that cellphones cause cancer.

• 20% believe doctors and health officials push child vaccines even though they "know these vaccines cause autism and other psychological disorders."

• Smaller numbers endorse theories involving fluoride, genetically modified foods and the deliberate infection of African Americans with HIV.

• 49% believe at least one of the theories and 18% believe at least three.

"There are a lot of people out there that harbor these beliefs," Oliver says, even in the face of scientific evidence to the contrary – such as the many studies showing no link between autism and vaccines.

Additional research shows similar numbers of people believe political conspiracy theories, Oliver says.

Where do people get this stuff? When it comes to health, sources include friends and family, but also celebrity doctors online and on TV, according to survey results not included in the research letter, Oliver says.

The beliefs also go along with certain health behaviors, the survey found. Those who believe at least three health conspiracy theories are less likely to use sunscreen, get flu shots or get check-ups and are more likely to use herbal remedies and eat organic foods.

"What we take away from that is that people who embrace these conspiracies are very suspicious of traditional evidence-based medicine," Oliver says.

Some of those people already have read about the study and contacted Oliver to share additional theories.

"My inbox this morning was flooded," he says.