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Dianna Kenny, PhD



The term social contagion describes the “spread of phenomena (e.g., behaviours, beliefs, and attitudes) across network ties”[1] (p. 556). Using very large datasets (e.g., Framingham Heart Study) that have collected longitudinal data on original participants (Original cohort), as well as their children (Offspring cohort) and their children’s children (Third generation cohort) and including their spouses, siblings, friends and neighbours, Christakis and Fowler have shown that social network effects, known as clustering, remain strong and can extend to those up to three degrees of separation from the original cohort. Such effects have been demonstrated across a large range of factors by different researchers using differing datasets. Examples include overweight/obesity, sleep patterns, smoking, alcohol abuse, alcohol abstention, marijuana use, loneliness, happiness, depression, cooperation, and divorce among others. Social contagion may apply to gender dysphoria and its rapid, epidemic-like spread across the Western world among adolescents and young people.

Social network analysis, the method applied to study contagions of all kinds, was first developed and used in public health as a way of determining patterns in the spread of diseases (e.g., influenza, HIV/AIDS, COVID) that resulted in pandemics. Its applications have since expanded with the advent of computers, the internet, mobile and smartphones, and social media.  

There are three types of social networks; (i) egocentric (networks assessing a single individual); (ii) sociocentric (social networks in a well-defined social space, such as a hospital or a school); and (iii) open system networks (e.g., globalised markets, social media). Each network consists of nodes (members), ties (between nodes), and measures of centrality, density and periphery or distance between the nodes. Networks with high centrality are the most effective in disseminating information or innovation. A key example is the transactivist lobby that has achieved spectacular success in a short time in changing health care, educational practices and legislation related to transgender individuals. Other characteristics of networks include cohesion (number of connections within a network) and shape (distribution of ties within the network)[2].

There is mounting evidence that the same principles of social contagion apply to and at least partially explain the increase in young people who believe that they are transgender.

Mechanisms of social contagion

  • Peer contagion

Peer contagion is a form of social contagion, defined as a process of reciprocal influence to engage in behaviours occurring in a peer dyad that may be life-enhancing (e.g., taking up a sport, studying for exams, health screening, resisting engaging in negative behaviours, altruism) or life-compromising (e.g., illegal substance use, truanting from school, aggression, bullying, obesity).  Peer contagion has a powerful socializing effect on children beginning in the pre-school years. By early childhood, the time spent interacting with same-age playmates frequently exceeds time spent with parents[3]. Further, characteristics of peer interactions in schools (e.g., aggression, coercive behaviours, mocking peers) are carried over into the home environment[4]. By middle childhood, gender is the most important factor in the formation of peer associations, highlighting the significance of gender as the organizing principle of the norms and values associated with gender identity[5].

  • Deviancy training 

Different mechanisms of transmission of peer influence have been identified. Deviancy training, in which deviant attitudes and behaviours are rewarded by the peer group, has a significant effect on the development of antisocial attitudes and behaviours such as bullying, physical violence, weapon carrying, delinquency, juvenile offending, and substance abuse[6]. Aggression in adolescence becomes more covert and deliberate and takes the form of exclusion, spreading rumours, and suborning relational damage among an adolescent’s friendship network[7]. Interestingly, adolescents associated with peers who engage in instrumental aggression become more instrumentally aggressive, while those associated with peers who engaged in relational aggression become more relationally aggressive, demonstrating the specificity of the effects of peer contagion via the deviancy training. 

  • Co-rumination 

Another form of peer contagion in adolescence is co-rumination, a process of repetitive discussion, rehearsal, and speculation about a problematic issue within the peer dyad or peer group that underlies peer influence on internalizing problems such as depression, anxiety, self-harm, suicidal ideation, and suicide[8]. Co-rumination is more common among adolescent girls[9]  although a similar phenomenon among boys has been observed. Being in a friendship that engages in perseverative discussions on deviant topics has been associated with increased problem behaviour over the course of adolescence. The longer these discussions, the greater the association with deviant behaviour in later adolescence6.

Peer contagion may undermine the effects of positive socializing forces such as schools, rehabilitation programs for young offenders, and treatment facilities for eating disorders, among others. Collecting same-minded adolescents into group programs may be counter-productive because the peer influence impacts of a homogeneous peer group to maintain disordered behaviours may be greater than the program effects of the treatment facility6.

Young people are particularly vulnerable to peer contagion if they have experienced peer rejection, hostility, and/or social isolation from the peer group[10]. On the contrary, protective factors against peer contagion effects include secure attachment to parents, adequate adult supervision and oversight of the young person’s activities, school attendance, and the capacity for self-regulation[11].

 Does social contagion have a causal effect on behaviour uptake?

Establishing a causal role for the effect of peer behaviour on adolescents is difficult because adolescents choose their peer networks; that is, they choose to associate with like-minded adolescents and those exhibiting similar attributes (homophily). This raises the question: Do adolescents choose their peers because they sanction and engage in similar behaviours or can peer social networks explain the uptake of (new) behaviours in individuals in the network? Sophisticated statistical models have been used to tease out the relative contributions of peer selection and peer influence. Correctly attributing the effects of these two factors has important policy implications since most interventions for reducing risky behaviour among adolescents are implemented at the school level[12].

The special case of social contagion via social media

In the world of social media, social contagion takes on a new, less complex, and narrower meaning:

“Unlike the broadcasts of traditional media, which are passively consumed, social media depends on users to deliberately propagate the information they receive to their social contacts. This process…can amplify the spread of information in a social network”[13] (p. 1).

For example, the social network ‘Instagram’ is one of the most popular platforms for adolescents and young people, with 44% reporting Instagram to be an important part of their daily lives[14]. Analysis of content shows that it is a major vehicle for the sharing of mental health issues, including depression, eating disorders, and non-suicidal self-injury (NSSI)[15].

Systematic reviews have identified potential risks and benefits of online activity. On the one hand, it reduces social isolation and offers encouragement, camaraderie, and reduction of self-harm impulses. On the other, it enables, enhances, or triggers potential risks of ‘copycat’ behaviours such as NSSI, suicide, and eating disorders through normalization of pathological behaviours, or vicarious and social reinforcement of these behaviours[16].

Evidence for social contagion among adolescents

Although social ties are generally protective against loneliness, depression, and suicide, social ties can be toxic and can amplify the risk of psychopathology in members of a social network[17]. There is growing evidence of social contagion among adolescents for several psychopathologies that arise in adolescence [e.g., eating disorders[18], marijuana use[19], non-suicidal self-injury16,[20],[21],[22],[23]; and suicide[24],[25]. Intensification of peer influence in closed communities of like individuals, such as schools, inpatient wards, residential units[26], or therapy groups often results in the advocacy of the practices (e.g., self-starvation, compulsive exercise, deceitful practices around eating) associated with anorexia nervosa6. Celebrity suicides also trigger spikes in suicide rates, with the greater visibility of the celebrity and prolonged coverage of the suicide triggering higher spikes and longer duration of elevation of rates of suicide amongst fans[27],[28].

Commentators on the burgeoning incidence of young people claiming that they are transgender assert that peer contagion may underlie this ominous trend.  When we examine the gender dysphoria epidemic in social network terms, we see several features operating. It is an open-system network with nodes and ties expanding across the oceans to the US, UK, Asia, Europe, Scandinavia, and Australia. Most countries are reporting sharp increases in the number of people seeking services and treatment for gender dysphoria. Many are ramping up services and setting up new gender clinics to cope with increased demand. This network is highly centralised with only one voice – the transactivist lobby.  Opinion leaders operating at the centre of these networks are very influential. The level of density in a network has two effects – firstly, it enhances the circulation of information between members and secondly, it blocks the introduction of dissenting ideas and evidence[29], both observable phenomena in the transgender epidemic. 

There is evidence that peer contagion may be a relevant factor in the sharp increases in young people vulnerable to succumbing to gender dysphoria.

  • Low gender typicality, peer victimization, ingroups and the trans-lobby

Low gender typicality (i.e., perceived lack of fit within one’s binary gender) has a significant impact on social acceptance within one’s peer group[30]. It is strongly associated with adjustment difficulties, behavioural problems, lower self-esteem, and increased internalizing disorders (e.g., anxiety, depression)[31]. As children progress to adolescence, peer as opposed to parental acceptance becomes paramount. Peers therefore take over the role of gender socializing agents from parents[32]. Adolescent peers tend to be critical of behaviours, dress, mannerisms, and attitudes that are not gender typical as a way of policing and reinforcing gender norms and respond with criticism, ridicule, exclusion, and even intimidation of non-conformers[33]. Research shows that the problems accruing to low gender typicality are mediated by peer victimization and that reducing peer victimization may ameliorate these difficulties29. Conversely, peer acceptance mediated the self-worth of gender non-conforming 12- to 17- year-olds[34]. Gender non-conformity and gender atypicality have also been associated with higher physical and emotional abuse by caregivers[35]. Mental health is difficult to sustain in the face of caregiver abuse and peer bullying and victimization[36]. Indeed, gender non-conforming and gender atypical youth are at higher risk of depression, anxiety, and suicidality in adulthood[37].

It is tempting to speculate that these groups of young people, searching for homophily (i.e., like peers) started to exaggerate their points of difference from their gender-conforming peers rather than to hide and minimize them to avoid being bullied and excluded. In so doing, they left the “outgroup” of nonconformers and formed an ingroup of extreme gender-nonconformers, transcending the gender barrier altogether and declaring themselves transgender. Suddenly, the discomfort and fear of not being gender typical becomes a virtue and rather than fearing the disapprobation of their peers, their open revolt in declaring themselves transgender is valorised by a politically powerful transactivist lobby. One would expect that gender atypical children who feel both internal and external pressure to be gender conforming would experience greater discomfort[38] and therefore be more susceptible to the message of trans activism. 

Ingroups behave in stereotypical ways with respect to outgroups – they favour ingroup characteristics, assigning more positive attributes to its members and derogating outgroups in order to enhance the status of their ingroup[39]. It is not surprising, then, that members of the transgender ingroup exaggerate the characteristics of the “trans” gender they take on – becoming more “feminine” or “masculine” than heteronormative groups of cismen and ciswomen. Transactivist groups have proliferated and consolidated in a short time by exploiting the characteristics of ingroups and outgroups. For example, social projection (i.e., the belief that other members of the group are similar to oneself) has been a powerful integrating process that simultaneously creates protection for its own members and distance from outgroup members, using the formula, “if you are not with us, you are against us” – those disagreeing with the ideology of the trans-lobby are labelled “transphobic” or TERFS (trans-excluding radical feminists) and publicly denounced. 

  • Rapid onset gender dysphoria (ROGD) and the role of social media 

The upsurge in rapid onset gender dysphoria (ROGD) tends to occur mostly in girls at around age 14, which is an age identified by developmental psychologists to be particularly susceptible to peer influence[40]. For example, a study of peer contagion for risky behaviours found that exposure to risk-taking peers doubled the amount of risky behaviour in middle adolescents, increased it by 50% in older adolescents and young adults, and had no impact on adults[41]. This group of young people were likely to belong to peer groups in which one or more of their friends had become gender dysphoric or transgender identified. Their coming-out announcement to parents also tended to be preceded by recent increases in their daughters’ social media and internet usage.  

Lisa Littman[42] canvassed the perceptions of parents who had children who displayed ROGD during or just after puberty. There were 256 respondents, of whom 83% had daughters, with a mean age of 15.2 years when they declared themselves transgender, 41% of whom had previously expressed a non-heterosexual sexual orientation, and 62.5% of whom had received a diagnosis for a mental health disorder (e.g., anxiety, depression) or a neurodevelopmental disability (e.g., autism spectrum disorder).  Thirty-seven percent (37%) of these young people belonged to peer groups with other members identifying as transgender. Parents also reported a decline in their child’s mental health (47%) and relationship with parents (57%) after declaring themselves transgender. Thereafter, they preferred transgender friends, websites, and information coming from the transgender lobby. 

Recent studies show that contagion is enhanced when online influencers are perceived to have high credibility and reduced when the influencer is perceived to have low credibility. A similar effect is observed if the influencer belongs to an out-group or an in-group[43].

Empirical evidence 

There has been a sharp increase in the population estimates of those identifying as transgender. One study, a meta-regression of population-based probability samples provides compelling evidence of this trend, where estimates more than doubled in the space of eight years from 2007 to 2015[44].

Similarly, upward trajectories of enrolments in GD clinics have been observed in the UK and Australia. Figure 1 summarizes the trends.

Figure 1

Source: Kenny, D.T. (2021). Australian data provided by the gender clinics under freedom of information applications and NIH for UK figures.



Gender dysphoria and its associated ideology highlights yet another worrying psychic epidemic affecting primarily young people that has spread its tendrils into all corners of society – medical, social, legal, psychological, political, ideological, and philosophical. We still do not understand this phenomenon well but there are sufficient indicators with respect to its trajectory to conclude that social contagion is a major player in its dissemination. 


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