People who lie about their health in order to get into medical research studies can mess up study results, and potentially make drugs appear more safe or effective than they really are — or less so, researchers say.

Some people may stretch the truth, or outright lie, because they want to participate in a study that pays money to its participants, said a paper published today (Sept. 23) in the New England Journal of Medicine.

In fact, in a 2013 study of 100 people who frequently participated in research trials, a quarter of the subjects said they had exaggerated symptoms, and 14 percent admitted they had pretended to have a health problem they didn't have, to get into a study. In addition, more than 40 percent said they had participated in two studies at the same time, without telling the researchers.

"Fabrication or falsification of information by research participants can undermine the integrity of a study," the researchers — David Resnik, a bioethicist at the National Institute of Environmental Health Sciences, and David McCann, of the National Institute on Drug Abuse — wrote in the new paper.

For example, say a study of a drug's effectiveness included a few people who only pretended to have the health condition that the drug aimed to treat. These participants would be "destined to succeed," regardless of whether they took the drug or a placebo, Resnik and McCann said. This could mean that the drug would appear less effective than it really is.

"As a result, pharmaceutical companies may inappropriately discontinue the development of effective medications, preventing patients from receiving valuable new treatment options," the authors said.

It's also possible that when study participants take part in more than one trial at a time, a harmful side effect might be attributed to the wrong drug, the authors said. [How 8 Common Medications Interact with Alcohol]

In addition to potentially compromising the study results, participants put themselves at risk when they lie. For example, they may not reveal pieces of their medical history that would increase their risk of experiencing harmful side effects from a particular treatment, a disclosure that would disqualify them from the study.

In a sleep study in 1980 that involved taking lithium, one participant did not tell researchers that she previously had anorexia and bulimia, which can lead to imbalances in important minerals such as potassium. Lithium is not recommended for people with low potassium, and the patient would have been excluded from the study if the researchers had known about her history of eating disorders. During the trial, she suffered cardiac arrest and died, the authors said.

Resnik and McCann recommended that researchers perform physical exams and laboratory tests on trial participants as a way to verify what those participants say about themselves. This could increase the costs of the study or the burden on research participants, but such costs would be justified because the information would protect participants and help ensure the study's integrity, the authors said.

Researchers may also want to consider providing rewards for participants who tell the truth, Resnik and McCann said. For example, researchers could tell participants that they will be given a blood test during the study to check for prohibited medications, and then provided with rewards such as cash or gift certificates if the results show they are not taking other medications, the authors said.

Researchers could also require that study participants have their information put into a database of all trial participants in all studies across the country, so that researchers could check whether participants were signed up for multiple studies at the same time, the authors said. This would also help researchers ensure that enough time had passed between trials, so that the effects of one trial would not overlap with another, the authors said.

The United States currently does not have a national database of research participants, but establishing one "could play an important role in promoting research integrity and protecting subjects from harm," Resnik and McCann said.

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