Psychological Impact Of Health Misinformation: A Systematic Review

Health misinformation refers to false, inaccurate, or misleading information about human health, including diseases, treatments, nutrition, and environmental factors that influence health outcomes.

The spread of health misinformation can negatively impact individuals’ beliefs, attitudes, and behaviors, potentially leading to poor health decisions and public health consequences. Misinformation often employs persuasive tactics to undermine scientific consensus and promote misconceptions.

Schmid, P., Altay, S., & Scherer, L. D. (2023). The Psychological Impacts and Message Features of Health Misinformation. European Psychologist, 28(3), 162–172. https://doi.org/10.1027/1016-9040/a000494

Key Points

• This systematic review synthesized evidence from 64 randomized controlled trials (RCTs; N = 37,552) on the psychological impact of health misinformation and analyzed message features of the misinformation using the FLICC framework.
• Exposure to health misinformation can indirectly damage healthy behaviors by negatively influencing psychological antecedents like knowledge, attitudes, intentions, perceived norms, trust, and emotions. However, these effects are context-specific.
• Few RCTs have evaluated the impact of misinformation on actual health behaviors. There is a lack of research on how misinformation influences perceived norms, emotions, and trust.
• Most research focused on vaccination, infectious diseases, and climate change. More studies are needed on topics like nutrition, non-infectious diseases, and substance use.
• The FLICC framework revealed common misinformation tactics, but few studies tested less prevalent tactics like impossible expectations and cherry-picking. Mapping tactics can guide counter-misinformation interventions.

Rationale

The World Health Organization (WHO) has called misinformation a major threat to global health, spurring research into its prevalence and correlational impacts (Suarez-Lledo & Alvarez-Galvez, 2021; Luk et al., 2021).

However, the mere existence of misinformation doesn’t prove harm, and correlational data provides limited causal evidence (Ecker et al., 2022).

To address this, the authors systematically reviewed randomized experiments on the causal impacts of health misinformation exposure.

They also classified the rhetorical tactics used in misinformation stimuli. Understanding both the impacts and features of misinformation can inform interventions to mitigate harm.

Method

The authors searched Medline, PsychInfo and Scopus databases using terms reflecting misinformation and RCT designs.

After removing duplicates, two raters independently screened titles, abstracts and full-texts using pre-defined exclusion criteria. Disagreements were resolved through discussion. The review process was guided by PRISMA.

From the final 45 articles reporting 64 RCTs, the authors extracted data on publication year, sample characteristics, outcome variables, misinformation stimuli, and effect sizes.

Outcomes were coded using an extended Theory of Planned Behavior (TPB) framework. Misinformation stimuli were classified using the FLICC framework of science denial tactics.

Search Strategy and Terms

Generic search terms included variants of “misinformation”, “misleading”, “randomized controlled trial”, and terms for health and environmental topics.

Full search strings for each database are provided. Peer-reviewed filter was used when available. No date restrictions were applied.

Inclusion and Exclusion Criteria

Studies were included if they used an RCT design to compare exposure to health misinformation versus a neutral control and measured impacts on behavior or its psychological antecedents.

Studies comparing misinformation to debunking or other interventions without a neutral control were excluded.

Results

Most studies (60/64) used online adult samples, predominantly from the Americas and Europe. Vaccination, infectious diseases, and climate change were the topics studied the most.

Impact of Misinformation

1. Behavior: The review found that the impact of health misinformation on actual behavior was rarely studied, with only two RCTs measuring activism behaviors and none directly evaluating health behaviors. This lack of behavioral evidence limits our understanding of the real-world consequences of misinformation exposure.
2. Intention: Intentions, attitudes, and knowledge were the most frequently measured outcomes. Exposure to misinformation decreased healthy intentions in some studies, but the majority found no effect or mixed results. Similarly, while some evaluations found that misinformation reduced positive attitudes or factual knowledge, many studies reported no impact or inconsistent findings.
3. Attitudes: Intentions, attitudes, and knowledge were the most frequently measured outcomes. Exposure to misinformation decreased healthy intentions in some studies, but the majority found no effect or mixed results. Similarly, while some evaluations found that misinformation reduced positive attitudes or factual knowledge, many studies reported no impact or inconsistent findings.
4. Norms: Few studies assessed the impact of misinformation on perceived norms, emotions, and trust, despite their theoretical importance in science denial and behavior change. The handful of studies that did measure these outcomes provided some evidence that misinformation can decrease perceptions of scientific consensus, evoke negative emotions, and erode trust, but more research is needed.
5. Control: Only one study measured perceived behavioral control, finding no effect of misinformation exposure.
6. Emotions: 4 evaluations. 1 increased negative emotions, 3 mixed.
7. Trust: 8 evaluations. 1 decreased trust, 1 conditional.
8. Knowledge: 53 evaluations. 23 found decreased accuracy judgments or belief in facts, 4 conditional, 20 no effect, 9 mixed.

Message Features of Health Misinformation

1. Logical Fallacies and Misrepresentations: Logical fallacies were the most common tactic, found in 41 out of 57 unique misinformation messages. For example, a study found that labeling sugar as “fruit sugar” made people perceive a food product as healthier, demonstrating an “appeal to nature” fallacy.
2. Impossible Expectations: Only two instances of misinformation involved demanding unrealistic scientific standards. One example criticized health professionals for promoting vaccines without absolute certainty about potential side effects, which decreased positive attitudes and increased anger towards vaccination.
3. Conspiracy Theories: Conspiracy theories were identified in 17 cases, mostly related to vaccination, infectious diseases, and climate change. For instance, exposure to a conspiracy claiming that the Zika virus was intentionally spread via genetically modified mosquitoes increased belief in this conspiracy.
4. Cherry Picking: Selective presentation of data was found in 10 misinformation messages, predominantly concerning vaccination or climate change. One example involved former President Trump drawing false conclusions about climate change based on short-term weather events, ignoring long-term climate data.
5. Fake Experts: 17 examples involved using fake experts to undermine scientific consensus. The Oregon Global Warming Petition, which claims to have over 31,000 scientists questioning human-caused climate change, was shown to decrease perceived scientific consensus despite only 0.5% of signatories having relevant climate science backgrounds.

Insights

Overall, the results suggest that misinformation can negatively influence the psychological antecedents of health behaviors, but the effects are inconsistent and highly dependent on contextual factors such as audience characteristics and message content.

The limited evidence on behavioral impacts and the scarcity of research on certain key outcomes (e.g., emotions, trust) highlight the need for more comprehensive and ecologically valid research to fully understand the consequences of health misinformation.

However, the review reveals critical gaps. Impacts on trust, emotions, and norms are understudied relative to their theorized importance in science denial (Jylhä et al., 2022). Intentions, the strongest psychological predictor of behavior, were rarely measured for environmental behaviors.

Crucially, there is virtually no experimental evidence that exposure to misinformation changes health behavior, which is the ultimate concern.

The lack of diversity in health topics, samples, and methods is concerning. Most studies involved online American adults and vaccination. More research on nutrition, chronic diseases, substance use, and other globally burdensome issues is needed, using representative samples across ages, cultures, and nations.

Future experiments should isolate the impacts of different FLICC tactics and potential moderators like worldviews.

Longitudinal and behavioral research is essential to understanding real-world impacts. The planetary health perspective could increase relevance across ideological audiences.

Strengths

• Used rigorous RCT evidence to evaluate causal impacts
• Analyzed both impacts and message features in one review
• Applied theoretical frameworks (extended TPB, FLICC) to synthesize findings
• Included both health and environmental domains for comprehensive view
• Detailed reporting of search process, study characteristics and effects

Limitations

• Few RCTs measured actual behavior or long-term impacts
• Skewed heavily toward online American adult samples
• Many health domains unstudied or understudied
• Some FLICC tactics and outcome categories had few cases
• Potential publication bias toward significant findings

Clinical Implications

This review provides health communicators and policymakers with crucial insights into the risks of health misinformation and common deceptive tactics.

It can guide the design of preemptive inoculation or reactive debunking interventions, especially those emphasizing scientific consensus and addressing logical flaws.

However, the lack of behavioral evidence means the societal harm of misinformation exposure remains unclear. The conditional nature of effects also means interventions must be carefully tailored to audiences. Persuasion is not one-size-fits-all.

Most importantly, this review is a roadmap for critical research gaps that must be filled to support evidence-based counter-misinformation efforts.

More diverse health issues, populations, settings and outcomes need rigorous study, especially using behavioral and longitudinal designs. Collaborations between health and environmental researchers could accelerate progress.

Communicators and scientists cannot avoid this challenge. Misinformation is undermining core foundations of public health. But this review shows the limits of current knowledge.

Far more research is needed to meet the “infodemic” with an evidence-based response.

References

Primary reference

Schmid, P., Altay, S., & Scherer, L. D. (2023). The Psychological Impacts and Message Features of Health Misinformation. European Psychologist, 28(3), 162–172. https://doi.org/10.1027/1016-9040/a000494

Other references

Ecker, U. K. H., Lewandowsky, S., Cook, J., Schmid, P., Fazio, L. K., Brashier, N., Kendeou, P., Vraga, E. K., & Amazeen, M. A. (2022). The psychological drivers of misinformation belief and its resistance to correction. Nature Reviews Psychology, 1(1), 13–29. https://doi.org/10.1038/s44159-021-00006-y

Jylhä, K., Stanley, S., Ojala, M., & Clarke, E. (2022). Science denial: A narrative review and recommendations for future research and practice. European Psychologist.

Luk, T. T., Zhao, S., Weng, X., Wong, J. Y.-H., Wu, Y. S., Ho, S. Y., Lam, T. H., & Wang, M. P. (2021). Exposure to health misinformation about COVID-19 and increased tobacco and alcohol use: A population-based survey in Hong Kong. Tobacco Control, 30(6), 696–699. https://doi.org/10.1136/tobaccocontrol-2020-055960

O’Keefe, D. J. (2002). Persuasion: Theory and Research. SAGE.

Suarez-Lledo, V., & Alvarez-Galvez, J. (2021). Prevalence of health misinformation on social media: Systematic review. Journal of Medical Internet Research, 23(1), Article e17187. https://doi.org/10.2196/17187

Keep Learning

1. Based on this review, what types of studies are most needed to advance understanding of health misinformation’s impact? How would you design these studies?
2. The authors suggest using a “planetary health” framing to make environmental and health behaviors more personally relevant across ideological divisions. Can you think of examples of how this could be applied to increase the effectiveness of fact-based messaging on polarized issues?
3. Many of the strongest effects of misinformation were conditional on audience characteristics, such as prior beliefs. What strategies could communicators use to tailor persuasive messaging when an audience resists the message?
4. The review found intentions, a key driver of behavior, were rarely studied for environmental issues, while norms, a key driver of health behaviors, were understudied for health. Why do you think this gap exists? How could integrating research approaches across domains fill important knowledge gaps?