When Homer composed The Iliad, he opened his epic not merely with a devastating plague sent by Apollo to decimate the Greek army, but with the bitter political conflict it ignited among its leaders. Centuries later, history mirrored myth during the COVID-19 pandemic. Alongside the immediate biological threat of the virus, a parallel crisis unfolded across the globe: an “infodemic” marked by deep social fragmentation and the rapid proliferation of anti-vaccine conspiracy theories.
While much of the public debate and media coverage centered on wild claims—such as vaccines containing microchips or mind-control technology—a landmark five-year longitudinal study from Japan provides a crucial reality check. Published in Scientific Reports, the study reveals that the true driver of vaccine conspiracy beliefs is not an sudden surge of fringe internet narratives, but rather an enduring, deep-seated distrust of mainstream media and government institutions.
Led by Professor Hitoshi Yamamoto of Rissho University, alongside Takahisa Suzuki, Yuki Ogawa, and Ryohei Umetani, the research tracks the psychological and media habits of Japanese citizens across five annual waves from April 2020 through April 2024. By observing the same individuals over half a decade, the team offers one of the most comprehensive longitudinal accounts to date of how conspiracy thinking takes root and evolves.
Disentangling Distrust from Delusion
To evaluate how conspiracy beliefs take shape, the researchers analyzed responses to the eight-item Anti-vaccine Conspiracy Belief Scale. A factor analysis revealed a vital empirical distinction: vaccine conspiracy beliefs do not exist along a single, uniform spectrum. Instead, they break down into two qualitatively distinct dimensions:
- Institutional Conspiracy Beliefs: Rooted in anti-establishment sentiment, these beliefs center on claims that real-world authorities—such as governments, academics, and pharmaceutical companies—systematically suppress negative information about vaccine risks or side effects.
- Implausible Conspiracy Beliefs: These involve extreme, scientifically outlandish narratives, such as claims that vaccines carry microscopic tracking devices or mind-control experiments aimed at monitoring citizens.
The study found a striking disparity between these two categories. While implausible conspiracy theories exhibited a pronounced “floor effect”—endorsed by only a tiny fraction of the population—institutional conspiracy beliefs showed broad variation across the sample.
Highlighting the importance of this finding, Professor Hitoshi Yamamoto noted in a press statement: “When people think about conspiracy beliefs, attention often focuses on highly extreme claims. However, our findings suggest that more common forms of conspiracy-related thinking are associated with persistent distrust of social institutions and the mainstream media. Addressing misinformation may therefore require not only correcting factual inaccuracies, but also understanding how distrust develops and persists within contemporary information environments”.
A Non-Western Perspective on Media Environments
Much of the existing research on misinformation has focused on highly polarized Western nations—particularly the United States—where partisan media ecosystems, selective exposure, and “echo chambers” are well-documented. Scholars like Cass Sunstein and Matteo Cinelli have demonstrated how social media algorithms reinforce pre-existing biases, insulating users from counter-narratives.
Japan, however, presents a distinct media context. The Japanese media landscape has traditionally been characterized by strong normative expectations of journalistic neutrality and substantial audience overlap across major news outlets. Despite this consensus-oriented media culture, COVID-19 vaccine conspiracy beliefs still gained traction.
By examining Japan, the researchers demonstrated that conspiracy beliefs do not depend solely on heavily segmented, partisan media ecosystems. As the authors note in the study, “institutional conspiracy beliefs were associated with lower reliance on mass media, persistent and growing scepticism toward mainstream media, and younger age. These findings suggest that institutional conspiracy beliefs reflect enduring orientations of distrust rather than temporary reactions to pandemic-specific information”.
Stable Trajectories vs. Temporal Fluctuations
To trace how beliefs evolved over time, the research team utilized Latent Growth Modelling (LGM). This advanced statistical technique allowed them to separate participants’ baseline attitudes in 2020 (intercepts) from their trajectories over the next four years (slopes).
The LGM results revealed that institutional conspiracy beliefs were strongly predicted by both high initial levels of media skepticism at the onset of the pandemic and significant increases in media skepticism between 2020 and 2024. Furthermore, individuals who consistently disengaged from traditional mass media—such as newspapers and television news—scored significantly higher on institutional conspiracy measures.
Interestingly, once cognitive-attitudinal factors like media skepticism were accounted for, the direct statistical effect of social media usage frequency diminished. This reinforces the conclusion that conspiracy endorsement is driven primarily by an underlying posture of institutional cynicism rather than mere passive consumption of online posts.
Regarding extreme narratives, the authors cautioned against overinterpreting high-visibility posts on social platforms. On networks such as X (formerly Twitter), automated bot accounts and algorithmic recommendation engines often amplify fringe content, creating a distorted perception of public consensus. As the paper stresses, “extreme and highly implausible conspiracy beliefs, although endorsed by only a small minority, may nevertheless attain disproportionate visibility in online environments”.
Psychological Foundations and Health Policy Implications
The study’s insights align with broader psychological literature on how humans respond to crisis. Classic research by Whitson and Galinsky established that when individuals experience a loss of control, their minds actively seek out patterns and alternative explanations to restore a sense of predictability. Public health emergencies naturally trigger feelings of powerlessness, prompting some individuals to adopt conspiratorial frameworks as a coping mechanism.
Moreover, psychological research by Karen Douglas and colleagues highlights that conspiracy theories fulfill epistemic, existential, and social needs. When official health messaging feels top-down or opaque, distrust in establishment motives can lead citizens to embrace anti-establishment narratives as a form of resistance.
For public health authorities and communication strategists, these findings signal a necessary shift in approach. Traditional anti-misinformation campaigns often prioritize fact-checking extreme claims or debunking viral myths. However, Yamamoto and his colleagues demonstrate that debunking fringe theories fails to address the root issue: the erosion of public trust in institutional actors.
To foster societal resilience against future health crises, experts advocate for proactive strategies such as psychological “prebunking” or inoculation—teaching the public to recognize manipulative rhetorical techniques before misinformation takes root. Crucially, institutions must prioritize transparency, acknowledge scientific uncertainty during evolving crises, and rebuild long-term credibility.
As the Japanese five-wave study proves, combating health misinformation is not simply a battle over facts; it is fundamentally a battle for institutional trust.
Endnotes
Lewandowsky, S., Ecker, U. K., & Cook, J. (2017).Beyond misinformation: Understanding and coping with the “post-truth” era. Journal of Applied Research in Memory and Cognition, 6(4), 353–369. https://doi.org/10.1016/j.jarmac.2017.07.008
Yamamoto, H., Suzuki, T., Ogawa, Y., & Umetani, R. (2026).Longitudinal predictors of vaccine conspiracy beliefs: findings from a five-wave panel study in Japan. Scientific Reports, 16, Article 23869. https://doi.org/10.1038/s41598-026-57049-5
Rissho University Press Release / EurekAlert! (2026).How do vaccine conspiracy beliefs develop? Five-year panel study in Japan reveals links with media skepticism. EurekAlert! Science News. https://www.eurekalert.org/news-releases/1138867
Homer. The Iliad. (Penguin Books, 1990). Original work published ca. 8th century BCE.
Douglas, K. M., Sutton, R. M., & Cichocka, A. (2017).The psychology of conspiracy theories. Current Directions in Psychological Science, 26(6), 538–542. https://doi.org/10.1177/0963721417718261
Whitson, J. A., & Galinsky, A. D. (2008).Lacking control increases illusory pattern perception. Science, 322(5898), 115–117. https://doi.org/10.1126/science.1159845
Sunstein, C. R. (2001). Republic.com. Princeton University Press.
Cinelli, M., Morales, G. D. F., Galeazzi, A., Quattrociocchi, W., & Starnini, M. (2021).The echo chamber effect on social media. Proceedings of the National Academy of Sciences, 118(9), e2023301118. https://doi.org/10.1073/pnas.2023301118
Asano, T.-A., Tago, A., & Tanaka, S. (2023).The Role of Public Broadcasting in Media Bias: Do People React Differently to Pro-government Bias in Public and Private Media? Political Behavior, 45, 1219–1240. https://doi.org/10.1007/s11109-021-09756-0
Kobayashi, T., Ogawa, Y., Suzuki, T., & Yamamoto, H. (2019).News audience fragmentation in the Japanese Twittersphere. Asian Journal of Communication, 29(3), 274–290. https://doi.org/10.1080/01292986.2018.1458326
van der Linden, S., Roozenbeek, J., & Compton, J. (2020).Inoculating against fake news about covid-19. Frontiers in Psychology, 11, 566790. https://doi.org/10.3389/fpsyg.2020.566790
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IMAGE CREDIT: NASA.
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