My brother is undoubtedly an intelligent individual—but he believes in some questionable things. Take, for example, his loyalty to two “psychic” twins on YouTube. These twins have hundreds of thousands of followers and fans who tune in to hear their predictions for the future. And while it’s unclear whether my brother actually believes everything these women say, he takes the time out of his day to listen to them—which alone is enough to make me question his rationality. Not to mention he researches and at least considers every conspiracy out there.

I joke and laugh with my brother about these interests of his, so long as they don’t prove harmful. But new research from the American Psychological Association sheds light on an interesting—and troubling—trend among individuals who engage in these conspiracy theories: they’re more likely to view vaccines as unsafe. “Vaccinations are one of society’s greatest achievements and one of the main reasons that people live about 30 years longer than a century ago. Therefore, it is fascinating to learn about why some people are so fearful of them,” lead researcher Matthew Hornsey, PhD, of the University of Queensland explains.

This study does not confirm or assert that one’s belief in conspiracy theories causes them to think negatively of vaccines, only that there is a link. The researchers discovered this link after surveying 5,323 people from 24 different countries and five continents. These questionnaires measured antivaccination attitudes, as well as beliefs in four popular conspiracy theories: the murder of Princess Diana; the American government’s knowledge of and role in the 9/11 attacks; the murder of John F. Kennedy as an elaborate plot; and the existence of a group of elites who are plotting a new world order.

The survey results showed that those with strong beliefs in these conspiracies were most likely to hold antivaccination attitudes, regardless of where they resided—however, level of education proved to have just a tiny impact on antivaccination attitudes. “People often develop attitudes through emotional and gut responses. Simply repeating evidence makes little difference to those who have antivaccination attitudes,” Hornsey says.

Hornsey goes on to explain that changing one’s conspiracy beliefs is a difficult feat: “Trying to reduce people’s conspiracy beliefs is notoriously difficult. An alternative possibility is to acknowledge the possibility of conspiracies, but to highlight how there are vested interests on the other side too; vested interests that are motivated to obscure the benefits of vaccination and to exaggerate their dangers.”

I find this study’s discoveries concerning, as they show that my brother’s interest or belief in conspiracy theories are linked to more troubling views such as vaccines being unsafe. While I can’t confirm if he does or doesn’t engage in this belief about vaccines, it’s something I plan to discuss with him, in an appropriate and effective manner. According to Hornsey, that involves acknowledging his beliefs and then making a case for the opposing view.

Hornsey, M., Harris, E., & Fielding, K. (2018, February 1). The Psychological Roots of Anti-Vaccination Attitudes: A 24-Nation Investigation. Health Psychology. Retrieved on February 2, 2018 from

American Psychological Association. (2018, February 1). Belief in Conspiracy Theories Associated with Vaccine Skepticism. [Press Release]. Retrieved on February 2, 2018 from