Functional neurological disorder (FND) is a relatively common reason for patients to present to neurology clinics and can present in varying ways including weakness, paralysis, seizures, and cognitive and sensory symptoms [1]. Previously described as an area of “forgotten” neurology [2], FND has undergone a renewed interest in the last decade, and there has been a significant evolution of the theories that influence our understanding of FND. It is described as a disorder involving abnormalities within and across areas implicated in attention, emotion processing, movement, and a sense of agency [1,3]. There remains, however, despite this increased interest, a limited awareness of FND among the general public, widespread disparity in clinical services for patients, and significant stigma [4,5]. Some of this stigma is driven by older paradigms of FND such as conversion disorder, “medically unexplained,” or “hysteria.” In the last 25 years, the disorder has been repositioned as one at the interface of neurology and psychiatry, where “brain” is just as important as “mind.” It is now a condition treated by many disciplines, not only mental health. Like many conditions in medicine, sex and gender issues also likely play a role in the perpetuation of stigma [6]. Women are more commonly affected than men, with rates broadly speaking about 70% women and 30% men, though this gender gap is narrower at different points in the lifespan [1].

FND may exist with other problems—common comorbid symptoms of FND include fatigue, cognitive symptoms such as attention and concentration difficulties, and sleep disturbance [1]. Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and long COVID, while distinct conditions, also share these core symptoms. Myalgic encephalomyelitis (ME) is typically diagnosed by features of debilitating fatigue, postexertional malaise, nonrefreshing sleep, and cognitive difficulties [7], while long COVID shares similar features [8]. There are further commonalities; FND, ME/CFS, and long COVID are often associated with significant disability, but not yet diagnosed by a distinct laboratory or radiological test, and are the subject of much debate [9]. Such debate has only heightened since the emergence of long COVID, with its associated chronic fatigue [10-12]. Some clinicians and researchers argue that a functional disorder paradigm may explain some cases of long COVID and ME/CFS [13,14], and some take the stance that it does not [15,16]. Some clinicians and researchers consider that these interrelated conditions have become inappropriately conflated and misunderstood, and FND has gotten mixed up and misrepresented in this debate [17,18]. These issues heighten vulnerability for patients with these conditions, turning to social media for information and support.

The clash of social media and medicine lies increasingly in the spotlight of late—especially in relation to public health and contentious illnesses [19-21]. Social networks generate pathways for the rapid spread of attitudes and information, and the internet forms a social network of tremendous scale. Dynamic factors are important—such as how users interact and engage with the information, leading to social reinforcement and weakening effects [22]. It has been shown that clusters within networks propel “bursts” of information, which spread rapidly [22]. Furthermore, users prefer data that reflect their own viewing history or align with personal views, introducing a degree of bias in what information is being seen and shared [23]. Some positives of social media dynamics include the ability to disseminate public vital information, target misinformation, foster supportive communities, and enable direct access to the newest health data and recommendations [24]. However, as shown in the case of the COVID-19 or 5G conspiracies [25], there are also several negative aspects, such as the fueling of falsehoods, cognitive overload, unverified testimonials, and rapid misinformation spread that undermines public health campaigns [24]. The natural human inclination of attention toward emotional or moral issues [26] can be harnessed to interact with algorithmic factors ultimately designed to capture user attention—in what has been dubbed the “human-algorithm interaction” [27].

While studies in this area in FND are few, it has been shown that some self-identified professionals have posted on the web in a way that was inaccurate and offensive about FND [28]. Content about functional disorders on the web is often conflictual and misleading [29], and patients with FND have described being “set back” in their recovery after encountering material about long COVID and FND on the web [30]. This landscape is concerning and raises important questions about who shapes these narratives and how they gain influence.

Influencers within social networks control the sharing and perception of information, regardless of its accuracy [25,31]. Influencers in social media research are often conceptualized as individuals with celebrity-like status, who carry a sense of authority [32,33], and have also been defined as users with credibility, who have a large and engaged following [34]. One type of health care influencer could be the “veteran patient” who shares their illness experiences on the web, building credibility, forming communities, and providing platforms for peer support, information exchange, and collective advocacy [35]. These highly visible figures often occupy structurally central positions within networks, which grants them both symbolic and relational power, enabling them to amplify their voices in ways that might not be possible offline [36]. In the context of our study, influencers are individuals with expertise in FND and related chronic illnesses, including researchers, practitioners, and patients or their advocates, who possess scientific knowledge, professional expertise, or lived experience.

Network science conceptualizes influence through structural positions that facilitate information diffusion, such as high centrality or bridging roles [37]. Opinion formation in such contexts is shaped not only by a small number of key influencers but also by the broader network of adopters of such opinions [38]. Communities may favor like-minded individuals and seek confirmation of their health beliefs on social media [39]. This perspective is particularly relevant in the context of discussions about FND on the web and related chronic illnesses, as social media provides a space accessible both to individuals directly associated with FND and to others with comparable lived experiences, even when some of these individuals express doubt about the very existence of FND. Accordingly, our key research objectives are to identify the key influencers within these networks and to examine the structure of the communities that emerge.

Understanding both the narratives and the network structures in which these popular users operate is crucial for analyzing how credible information is hindered and how misinformation spreads or remains contained. To our knowledge, the web-based communities in relation to FND have not been evaluated in this way, nor has the online content in relation to FND been described. We therefore aimed to study the way in which FND is described on 1 social media platform, X (formerly known as Twitter).

Our study found that discussions around FND on X are mainly shaped by individuals associated with other conditions, primarily patients who identify as having long COVID or ME or both. This was despite the web-based presence of reputable FND organizations and leading FND figures who had a large following. Our content analysis showed that similar issues affect those with long COVID and ME as people with FND, such as health care professional stigma and lower illness status [4,48].

Overall, in our study, the majority of influential users held doubts about the validity of FND as a whole. Some of this seemed to stem from historical aspects and was driven by misperceptions of how modern-day FND is understood, which is also a finding in the literature [4,6]. There was the presumption that clinicians who work in FND still cling to older paradigms that are stigmatizing, such as FND is no more than a name for the stereotype of hysteria, for example [6]. Attention toward FND perhaps implied a threat of diverting attention away from biomedical research and toward psychologically oriented interventions that were considered harmful by some users. These results, while found in the context of FND search terms, also may have implications for other chronic illness communities, particularly ME and long COVID, who are also exposed to these opinions and information on X.

The underlying tension between the 2 groups may be further driven by core factors around the conceptualization of illness, more generally [49,50]. The possibility of the interplay of psychological factors in FND seems to have been, broadly speaking, accepted by the FND community, whereas the patients with ME or long COVID continue to advocate for an exclusively biomedical understanding of their symptoms (on the web at least). Underpinning this was the view that symptoms that are deemed “psychological” seem to be conflated with “imaginary”—again, this is in keeping with what is reported in the scientific literature in relation to patients with FND, long COVID, and ME/CFS [4,51,52]. Any association with “psychological” was seen as an almost instant invalidation and dismissal and seemed to gain traction on social media in quite a forceful way.

On that note, it is possible that the role of the platform itself could be important in our study, where negative content may have been amplified by an X algorithm because of its more provoking nature [27]. Social media sites are designed to amplify emotive content, often regardless of its veracity. Social networks strongly influence political and health outcomes [53,54], and the social media industry has been described as a “commercial determinant of health” [54]. To take further some examples of this, vaccine uptake was negatively affected by misinformation on social media [55], and a recent study looking at the influence of X on psychiatric medication sales showed that Ritalin sales significantly increased, while sales of bupropion significantly decreased after Elon Musk posted his personal experience of them [56]. Furthermore, a recent discovery of the deliberate manipulation of algorithms to influence public discourse has raised growing concern about platforms like X [19,20]. Algorithmic factors are automated programs that allow for more personalized content to be fed to the user; this allows for the creation of highly polarized groups that spread information rapidly [57]. It has been shown on X that the latest posts on the user’s homepage were created according to the user’s likes, interests, most shared, liked, and replied to posts, and those accounts the user most interacted with [57,58].

Several studies explore the factors that influence how information and misinformation are shared on social media [27,59,60]. There are certain factors that make information more susceptible to amplification; from the individual’s perspective, such factors include motivation to socialize, trust in the information, desire for entertainment, and altruism [61]. It has been shown that negative content posted by public figures is more likely to be shared than that posted by “ordinary” users [62]. Psychological factors are important, with anger being shown to correlate with fake news sharing [63]. Cognitive bias, when people believe what aligns with their existing views or values, will also fuel increased engagement with certain posts [23].

On a more hopeful note, social media was used in a positive way by the FND community, as outlined by the findings of themes of solidarity and shared knowledge. This highlights that there is some usefulness to posting on social media, particularly during meetings or conferences [21,24]. Perhaps, it would be helpful for influential FND users to tag other illness groups during such events, which might enable a shared perspective in the future.

Given the expanding influence of social media on health and health care policy [64,65], this type of study is gaining more relevance for research and practice. This is a novel study; to our knowledge, there was no published study in the English language exploring how FND is discussed on the web using this type of approach. The data have limitations, as they are all self-declared, for example, role and diagnosis are not objectively verified. There were users who frequently posted about COVID-19 or ME/CFS, but did not obviously identify their role or condition, and were categorized as unknown due to conservative coding practice. Therefore, the proportion of individuals related to COVID-19 or ME/CFS is likely underestimated among such “unknown” accounts. The data were limited to a 2-month period and may not be representative of what is happening in other internet domains or offline. Furthermore, we did not use the term “dissociative disorder” as a search term—this is a broad term encompassing many different conditions such as dissociative identity disorder, among others, which, while related to FND, were not the subject of our investigation.

In conclusion, the space for individuals posting about FND on X is a concerning area. Given these findings, perhaps the key players in FND, be it organizations and professionals, could play more of an active role in disseminating evidence-based knowledge. In reality, this could mean interacting more on the platform rather than a one-off post or interacting with different illness groups [66]. Moderators and fact checkers of web-based platforms also have a key role in monitoring the spread of harmful health care information [67], though this is a controversial area, where the direction is changing rapidly [68]. Importantly, patients and their families should be informed about trustworthy sources and the risk of encountering invalidating material on the web. This study, though focusing on FND, has implications for other illnesses and could potentially be a template for evaluating how other stigmatized conditions are perceived on the web.