Health myths spread because several psychological, social, informational and technological mechanisms interact. A health myth is usually a widely repeated belief or claim that is inaccurate, unsupported or substantially misleading, although the term can be used more broadly for traditional misconceptions. Health information is unusually susceptible to myths because it concerns fear, survival, illness, family, identity and uncertainty, all of which create strong emotional responses. People also frequently encounter health claims when they are worried or searching urgently for explanations.
A simple, memorable story can therefore feel more satisfying than a complex explanation involving probabilities, uncertainty and multiple interacting causes. The spread of a myth does not necessarily indicate that people are irrational; it can reflect ordinary cognitive shortcuts operating in an information environment that rewards attention and repetition.
Emotional salience is one major driver. Claims involving danger, miracle cures, hidden causes, children, cancer or threats to personal safety can attract attention because humans are naturally responsive to potential threats. Strong emotional reactions can also increase memory and sharing. A cautious scientific statement such as “evidence remains uncertain and effects vary between populations” is harder to remember than an absolute statement such as “this substance causes disease” or “this treatment cures everyone”. This asymmetry can make simplified claims disproportionately visible. WHO describes how infodemics can rapidly amplify false or misleading information, particularly during health emergencies, when uncertainty and anxiety are already high.
Repetition can also make information feel familiar and therefore more believable, even when repetition does not add evidence. A claim encountered repeatedly across videos, posts, websites and conversations may appear to have independent support when many repetitions actually trace back to one original source. Social proof can reinforce this effect because people often infer credibility from the number of others appearing to believe or share something. Algorithms that prioritise engagement can further expose users to material that generates strong reactions. WHO has specifically highlighted the rapid spread of misleading information through digital environments and the importance of strengthening digital and health literacy as a response.
Confirmation bias contributes when people preferentially notice, remember and share information that fits their existing beliefs or expectations. If someone already believes that a particular food, treatment or institution is harmful or beneficial, evidence consistent with that belief may receive more attention than contradictory evidence. Motivated reasoning can make people scrutinise opposing claims more harshly than supportive ones. This does not mean that every belief is equally irrational or that all evidence is merely subjective. It means that evaluating evidence requires deliberate attention to methods, sources and contradictory findings rather than relying solely on whether a claim feels intuitively correct. Health literacy and critical appraisal skills can help counter these tendencies.
Personal anecdotes are particularly powerful sources of health myths because they are concrete, emotionally compelling and easy to understand. Someone may take a supplement and subsequently recover from an illness, then conclude that the supplement caused the recovery. But symptoms may have improved naturally, another treatment may have contributed, or the condition may have fluctuated. This is an example of post hoc reasoning: assuming that because one event followed another, the first caused the second. Individual experiences can be meaningful to the person who experienced them, but they generally cannot establish treatment efficacy or safety for a population. Controlled studies are designed specifically to reduce these kinds of causal errors.
Complexity creates another opening for myths. Many medical questions have conditional answers because effects depend on dose, age, baseline risk, genetics, disease subtype, duration and other factors. Myths often remove those qualifications and convert nuanced evidence into simple rules. Conversely, a technically correct fact can become misleading if presented without context. For example, a substance can be biologically active without being dangerous at every exposure level, and a treatment can have a benefit without benefiting every patient. Good scientific communication therefore needs to preserve the important conditions surrounding a finding while remaining understandable enough for people to use.
Commercial and ideological incentives can contribute to myth propagation. A business selling a supplement, diagnostic test or alternative treatment may have an incentive to emphasise benefits and minimise uncertainty. Content creators may benefit financially from high engagement, while political or ideological communities may use health claims to reinforce group identity. This does not mean that every commercial or ideological source is unreliable, but incentives are relevant when assessing selective presentation of evidence. WHO recommends considering the source, authorship, outlet and evidence behind health information and warns that misinformation can promote unproven treatments and harmful health behaviours.
Health myths can persist even after correction because correcting a claim requires more cognitive effort than repeating it, and people may remember the original statement while forgetting the qualification. Effective prevention therefore involves building health literacy before misinformation is encountered, improving access to understandable authoritative information, explaining uncertainty and encouraging people to pause before sharing. WHO recommends critical thinking, digital and health literacy, trusted sources and fact-checking as components of countering disinformation and misinformation. The most useful response to a myth is usually not merely to say that it is false, but to explain the underlying evidence, why the misconception is attractive, what is actually known and what remains uncertain.
