Experts call for action against imposter participants in health studies

Imposter participants threaten the integrity of health research and, by extension, the policies and clinical decisions built on it, warn experts in The BMJ.

Eileen Morrow and colleagues at the University of Oxford say the research community "must acknowledge the problem and dedicate resources to testing and implementing safeguards .. to ensure that the data guiding clinical care reflect the real patient voice."

Imposter participants are individuals who provide deceptive or inaccurate data to take part in health research or automated computer 'bots' that mimic human behavior and responses.

The issue has grown in recent years as online recruitment has become central to modern health research and can impact all types of studies, from surveys to randomized controlled trials.

The motivations of imposter participants remain unknown, explain the authors. Although some reports suggest that monetary benefit is a driver, not all studies offer financial incentives, so other motives, such as boredom, curiosity, or even an ideological intent to disrupt research, may also play a role.

Yet their impact is demonstrable. A 2025 review showed that 18 of 23 studies that looked for imposter participants in their data sets found them, with rates ranging from 3% to a high of 94%.

Researchers should routinely integrate imposter participant detection and prevention into online research, while considering the potential effect on their study population, write the authors. 

Common safeguards include identity verification procedures or CAPTCHA tests (asking participants to complete a task, such as to read and type distorted letters).

At a minimum, they say studies should transparently report which safeguards were used and acknowledge their limitations, and journals should encourage consistent and transparent reporting of these safeguards. 

Funders and institutions should also invest in infrastructure and training to help researchers keep pace with evolving tactics, while clinicians and policymakers should be cautious when interpreting studies that use online recruitment if imposter participant prevention is not mentioned.

They concluded, "Imposter participants are more than a nuisance; they are a systemic threat to health research. Their effect is demonstrable and their detection inconsistent. In an age where online recruitment underpins everything from randomized controlled trials to surveys, they risk undermining the integrity of health research and the decisions built on it."