Individuals frequently update their beliefs and behaviours based on observation of others' experience. While often adaptive, social learning can contribute to the development of negative health expectations, leading to worsened health outcomes, a phenomenon known as the nocebo effect. This systematic review and meta-analysis examined: whether social learning is sufficient to induce the nocebo effect, how it compares to other forms of induction (classical conditioning and explicit instruction), and factors that influence these effects. The meta-analysis included twenty studies (n = 1388). Social learning showed a medium-large effect size (Hedges' g = .74) relative to no treatment and a to small-medium effect (g = .42) when compared to neutral modelling. The effect of social learning was similar in magnitude to classical conditioning but greater than explicit instruction with a small-medium effect (g = .46). Face-to-face social modelling, longer exposure, higher proportions of female participants and models, and greater observer empathy led to stronger socially-induced nocebo effects. However, further research is essential as only a minority of studies measured important constructs like negative expectancies and state anxiety. Nonetheless, the study highlights social learning as a key pathway for nocebo effects, suggesting it as a target for interventions to reduce the substantial personal and societal burden caused by nocebo effects.

While social media exposure is known to influence vaccine hesitancy, its impact on postvaccination experience remains relatively unknown. This retrospective cross-sectional study explored whether various psychosocial and individual factors moderate the association between social media exposure to personal recounts of COVID-19 vaccine side effects and the viewer’s subsequent postvaccination side effect experience. Adults residing in Australia, who were fully vaccinated with two COVID-19 vaccine doses (n = 280) completed an online survey. The more severe the personal recounts of post-COVID-19 vaccination side effects participants were exposed to on social media, the more severe their own postvaccination side effects were following both their first (β = 0.261, p < 0.001) and second dose (β = 0.299, p < 0.001). This association was stronger among those with greater vaccine side effect worry, elevated negative emotional states such as anxiety and stress, and a stronger proclivity for using social media over mainstream media for COVID-19 vaccine side effect information. As such, not only does social influence appear to exacerbate or trigger postvaccination side effects, but a range of psychosocial and situational factors moderate this association. Health organisations and government bodies could minimise the negative effects of social media exposure in future health outbreaks by countering treatment misperceptions on social media platforms as they arise.

Background: Social learning can be highly adaptive—for example, avoiding a hotplate your friend just burnt themselves on—but it has also been implicated in symptom transmission. Social learning is particularly pertinent given the rapid increase in the use of online mediums for social interaction. Yet, little is known about the social transmission of symptoms online or social chains extending further than a single model–observer interaction. Purpose: To explore whether socially induced symptoms could be propagated through a three-generation social transmission chain in an online setting. Methods: We explored the social transmission of cybersickness following a virtual reality (VR) experience through online webcam interactions. One hundred and seventy-seven adults viewed a VR video in one of four links along a social transmission chain, after: viewing an actor model cybersickness to the VR video (First-Generation); viewing the First-Generation participant undergo VR (Second-Generation); viewing the Second-Generation participant undergo VR (Third-Generation); or naïve (Control). Results: Cybersickness was strongest in First-Generation participants, indicating social transmission from the model. This was mediated by expectancy and anxiety. Whether or not subsequent generations experienced cybersickness depended on what the observed participant verbally reported, which is consistent with social transmission. Conclusions: Results demonstrate that symptoms can be readily transmitted online, and that expectancy and anxiety are involved. Although it is inconclusive as to whether symptoms can propagate along a social transmission chain, there is some evidence of protection from symptoms when a model who does not report any symptoms is observed. As such, this research highlights the role of social transmission in the modulation of symptoms through virtual mediums.

Witnessing another’s pain can heighten pain in the observer. However, research has focused on the observer’s intrapersonal experience. Here, a social transmission-chain explored the spread of socially-acquired nocebo hyperalgesia. Dyads of genuine participants were randomised to ‘Generations’ (G1–G3). G1-Demonstrators, observed by G2-Observers, experienced high/low thermal pain contingent on supposed activity/inactivity of a sham-treatment. G2 became Demonstrators, witnessed by G3-Observers. They experienced fixed low-temperature stimuli irrespective of sham-treatment ‘activity’. G3 then Demonstrated for G4-Observers (a confederate), also experiencing low-temperature stimuli only. Pain ratings, electrodermal activity, and facial action units were measured. G1’s treatment-related pain propagated throughout the chain. G2 and G3 participants showed heightened subjective and physiological response to sham-treatment, despite equivalent stimulus temperatures, and G3 never witnessing the initial pain-event. Dyadic interpersonal physiological synchrony (electrodermal activity) and psychological synchrony (Observer’s ability to predict the Demonstrator’s pain), predicted subsequent socially-acquired pain. Implications relate to the interpersonal spread of maladaptive pain experiences.

Objective: Negative beliefs about medication and vaccine side-effects can spread rapidly through social communication. This has been recently documented with the potential side-effects from the COVID-19 vaccines. We tested if pre-vaccination social communications about side-effects from personal acquaintances, news reports, and social media predict post-vaccination side-effect experiences. Further, as previous research suggests that side-effects can be exacerbated by negative expectations, we assessed if personal expectations mediate the relationships between social communication and side-effect experience. Method: In a prospective longitudinal survey (N=551), COVID-19 vaccine side-effect information from three sources—social media posts, news reports, and first-hand accounts from personal acquaintances—as well as side-effect expectations, were self-reported pre-vaccination. Vaccination side-effect experience was assessed post-vaccination. Results: In multivariate regression analyses, the number of pre-vaccination social media post views (β = .17) and impressions of severity conveyed from personal acquaintances (β = .42) significantly predicted an increase in pre-vaccination side-effect expectations, and the same variables (βs = .11, .14, respectively) predicted post-vaccination side-effect experiences. Moreover, pre-vaccination side-effect expectations fully mediated the relationship between both sources of social communication and experienced side-effects from a COVID-19 vaccination. Conclusions: This study identifies links between personal acquaintance and social media communications and vaccine side-effect experiences and provides evidence that pre-vaccination expectations account for these relationships. The results suggest that modifying side-effect expectations through these channels may change the side-effects following a COVID-19 vaccination as well as other publicly discussed vaccinations and medications.

Individuals frequently update their beliefs and behaviours by utilising information learned from observing the experience of others. While often adaptive, social learning has been implicated in the formation of negative health expectations, which subsequently lead to poorer health outcomes, a phenomenon known as the nocebo effect. The present systematic review and meta-analysis sought to evaluate: (1) whether social learning is sufficient to induce the nocebo effect; (2) any difference in the magnitude of socially-induced nocebo effects relative to other forms of induction (i.e., classical conditioning and/or explicit instruction); and (3) situational and dispositional factors that moderate these effects. Following a systematic literature search, twenty studies (n = 1,388) were included in the meta-analysis. The effect size for social learning ranged from medium-large relative to no treatment control conditions (Hedges’ g = .74) to small-medium when compared to neutral modelling control conditions (g = .42). The effect of social learning was similar in magnitude to classical conditioning but greater than explicit instruction with a small-medium effect size (g = .46). Face-to-face social modelling, longer modelling manipulations, studies with higher proportions of female participants and models, and greater observer empathy led to stronger socially-induced nocebo effects. However, further research is essential as only a minority of studies measured important constructs like negative expectancies and state anxiety. Results nevertheless demonstrate that social learning is a key pathway through which individuals experience nocebo effects and should therefore be a target for interventions to reduce the substantial personal and societal burden caused by nocebo effects.