Two important, while relatively uncommon, outcomes of trauma include experiences of post-traumatic growth (PTG) and symptoms of post-traumatic stress (PTS; ^[1]). PTG is characterized by increased personal strength, a renewed sense of life purpose and meaning, and better interpersonal relationships ^[2]. In contrast, PTS is characterized by intrusive and unwanted memories of the traumatic experience, uncomfortable physical reactions including sweating and heart racing in response to trauma reminders or triggers, and more ^[3]. PTS is also commonly comorbid with heightened experiences of depression and anxiety ^[3]. While these two outcomes seem contradictory in their presentation, there is growing recognition that PTG and PTS are linked by similar underlying mechanisms and often co-occur in response to the same stressor ^[4]. Specifically, prior literature has identified several key cognitive variables as necessary prerequisites for the development of both PTG and PTS ^[5]. These include judgments of the centrality of the potentially traumatic event to one’s life, as well as perceptions that the event functioned to violate a core belief about oneself, others, and/or the world.

2. Event Centrality and Its Connection to PTG and PTS

The centrality of an event has been defined as “the degree to which an individual believes a negative event has become a core part of their identity” ^[6] (p. 107). Theoretically, this cognitive mechanism is an essential part of an individual’s progression towards both post-trauma outcomes, as noncentral events are not important enough to generate a strong or sustained post-traumatic response that requires cognitive attention (i.e., leading to either PTG or PTS). Consistent with this logic, greater perceived event centrality after a range of potentially traumatic events has been associated with increased levels of negative mental health consequences, including depression and PTS ^[7]. Likewise, judgments of event centrality have emerged as a unique theoretical and statistical predictor of PTG and PTS after experiencing an array of well-studied traumatic events, including death, serious accidents, physical or sexual assault, and wartime combat ^[8]. As PTG and PTS outcomes have been documented to be uncorrelated ^[9][10], it seems almost paradoxical that the centrality of an event could predict both. However, both outcomes are catalyzed by an event that is perceived as traumatic in a way that challenges existing cognitive paradigms (e.g., other people can be trusted, the world is safe, and good people cannot be harmed). Consistent with this supposition, judgments of greater event centrality have been associated with both a greater likelihood of intrusive ruminations about the event as well as increased probability that the person reports that the event violated one of their core beliefs ^[8]. However, less is known about whether judgments of event centrality, when applied to experiences of intimate partner infidelity (a non-Criterion A trauma that has been defined as a potentially traumatic event), will be associated with both of these post-trauma outcomes.

3. Infidelity as a Potentially Traumatic Event

Infidelity within an intimate relationship is typically described as an interpersonal betrayal. However, its lasting effects can resemble those experienced by individuals with PTSD in response to other traumas ^[11][12]. Moreover, while generally understudied in comparison to traumatic events that are officially named by the Diagnostic and Statistical Manual of Psychiatric Disorders (DSM), infidelity and relational problems are often cited as the most distressing life events experienced by both LGBTQ+ and heterosexual populations ^[13]. The DSM defines a traumatic event to include “actual or threatened death, serious injury or sexual violence”, and therefore, as per the DSM definition, infidelity cannot be characterized as a trauma. While the Substance Abuse and Mental Health Services Administration (SAMHSA) defines trauma as an “event, series of events, or set of circumstances that is experienced by an individual as physically or emotionally harmful or threatening and that has lasting adverse effects on the individual’s functioning and physical, social, emotional, or spiritual well-being” ^[14] (p. 2). Likewise, in leading definitions of trauma-informed care, trauma is defined as constituting the three E’s (event, experience, and effect). Therefore, this highlights the importance of considering an individual’s experience of the event and not simply the event itself when determining whether something is traumatic ^[15]. That being said, in the previous literature, infidelity has been considered in a variety of ways, including as a nontraumatic stressful event, an interpersonal trauma, and a potentially traumatic event (PTE) ^[16][17]. The trauma model of infidelity ^[18] likens the subjective experience of infidelity to the experience of a trauma, a position that has been adopted by many other scholars in the field of relationship science ^{[19][20][21][22]}. PTEs like infidelity have been shown to elicit similar levels of PTG as have other DSM-certified traumatic events ^[16]. Infidelity can function to rupture a strong interpersonal and romantic connection, which has been recognized as a vital component of an individual’s psychological well-being ^[23]. In line with betrayal trauma theory, infidelity can also have long-standing and widespread impacts on an individual’s ability to trust and receive comfort from others ^{[24][25][26][27]}. Betrayal is the cornerstone of experiences of infidelity, as it violates the trust that is crucial to adult romantic relationships. The intensity of the feeling of betrayal likely contributes to judgments of infidelity as a central experience in one’s life. Infidelity has also been linked with experiences of PTG, particularly as it influences the betrayed partner to redefine their values for what is sought in a romantic partner ^[28]. Experiences of infidelity within relationships have also been shown to lead betrayed partners to detach from the former relationship and become open to new romantic connections. This, in turn, can result in a better long-term interpersonal connection, a key component of PTG ^[28]. PTG as a result of infidelity has even been found in couples who remain together after infidelity, with forgiveness being a key predictor of that experience ^[29]. Some women who have been relationally betrayed have been shown to exhibit signs of PTG, with time being an important corollary to growth experiences ^[25]. Certain resources, like access to therapy, receiving psychoeducation, and experiencing support from and forgiveness for their partner, have been demonstrated to contribute to the development of PTG ^[25]. Overall, the experience of infidelity has been associated with both PTS and PTG, suggesting that designating this event as a PTE has validity.

4. Relationship Forms and Infidelity

While infidelity has been noted to contribute to PTS symptoms, this has primarily been demonstrated within marital relationships ^[25][27]. It is important to consider varying relationship dynamics, like lower levels of commitment, sexually permissive attitudes, and anxious attachment styles, that are present within college student couples that may put them at higher risk for experiencing infidelity ^[30][31], leaving them vulnerable to PTS. As demonstrated by Roos and colleagues ^[32], infidelity may produce PTS symptoms at a relatively high rate even in unmarried young adults, leading to poorer psychological health overall. Relationship forms have emerged as a parsimonious way to consider the level of entanglement between romantic partners. Postulated to fall loosely along a continuum of commitment, these forms include casually dating, exclusively dating, and engaged/married. Casually dating has been defined as a couple engaging in a romantic connection that may include sexual contact without clear intentions or expectations for exclusivity or monogamy ^[33]. Exclusively dating can be defined by increased seriousness or commitment when couples have increased emotional and physical intimacy and exclusivity, often with the expectation of a future, long-lasting relationship ^[33]. Engaged or married relationships involve the most entanglement, including increased romantic and physical intimacy, often in conjunction with shared logistical considerations (i.e., living together, children, and joint finances). Furthermore, as couples make the transition from “casual” to “exclusive” and “exclusive” to “engaged or married”, their intimacy and commitment increase ^[34]. These changes may be associated with differences in the perceived centrality of infidelity, as betrayal trauma theory states that betrayal within a “closer” relationship is more impactful on the individual ^[24]. Importantly, however, the strength of the relationship between judgments of centrality and PTG and PTS may vary by relationship form. Theoretically, infidelity occurring in a dating relationship in young adulthood may be particularly impactful, as the individual experiencing infidelity is likely to have less experience in romantic relationships broadly ^[32]. Conversely, it could also be hypothesized that infidelity in more established and publicly solidified relationships, like marriage, may be perceived as more central and impactful, given that marital infidelity might necessitate a change in housing, finances, or child custody ^[35]. Dissolving a marriage post-infidelity may also evoke a greater sense of betrayal and/or generate greater community, religious, or social responses, and these, in turn, may generate altered cognitions about the self, partners, or the world. Thus, there is theoretical debate about whether and how perceptions of infidelity as a central experience within different relationship forms may differentially relate to PTG and PTS.