Population estimates suggest that transgender and gender diverse people (herein “trans”) comprise 7.1% (486/6841) of Australia’s high school-aged population [1], 1.1% (22/2000) of adults aged 25‐44 years, and 0.5% (14/3003) of those aged 45 years and older [2]. These figures align with international estimates, which suggest that 0.5% to 4.5% of adults worldwide are trans [3]. Trans people are known to experience poorer mental health than their cisgender peers [4-6]. In the largest Australian survey of trans young people to date, 3 in 4 had ever been diagnosed with depression or anxiety and almost 1 in 2 had ever attempted suicide [5]. Comparable rates of depression (663/914, 73%) have been reported in trans adults, while 67% (613/914) have been diagnosed with anxiety and 43% (393/914) have attempted suicide [7]. When compared to the general adult population in Australia [8], self-reported rates of suicide attempts are 9 times higher in trans adults [9] and 10 times higher in trans young people [5].

Many trans people experience gender dysphoria [10], which refers to distress that arises from an incongruence between one’s experienced gender and one’s gender presumed at birth [11]. Gender dysphoria can be related to specific bodily characteristics (eg, the chest, hips, and voice), cultural expectations of gender, how others perceive a person’s gender (eg, “passing” as one’s affirmed gender), how a person is affirmed or not affirmed by others (eg, being gendered correctly or experiencing misgendering), or any combination of the aforementioned [12]. The onset or exacerbation of gender dysphoria is often associated with changes during puberty and the development of secondary sex characteristics [12], though both the DSM-5-TR (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision) [11] and the ICD-11 (International Statistical Classification of Diseases and Related Health Problems, Eleventh Revision) [13] state that gender dysphoria can also be diagnosed in earlier childhood. For instance, many trans people report their earliest experience of gender dysphoria as occurring between the ages of 3 and 7 years [14,15]. Gender dysphoria is associated with a number of negative mental health outcomes such as depression [16-19], anxiety [16-19], suicidal thoughts and behaviors [20,21], and poor quality of life [19].

In addition, gender dysphoria is associated with a number of risky behaviors, including nonsuicidal self-injury [17,21,22], disordered eating [23,24], compulsive exercise [25,26], low levels of physical activity [25], and substance use [27,28]. Behaviors such as nonsuicidal self-injury, disordered eating, and substance use are commonly used as coping strategies [29-32] and, as such, may be common among trans people seeking to manage the distress associated with gender dysphoria. However, many of these behaviors may also be used to alter one’s appearance in an attempt to meet the sociocultural appearance ideals of one’s gender. For example, some trans people report restricting their calorie intake or avoiding physical activity in order to be thin and avoid looking muscular, or to suppress curves [23,33], whereas others may engage in compulsive exercise to try to increase weight and muscle mass [34,35]. Additionally, some trans people assigned female at birth may avoid physical exercise that may trigger dysphoria by bringing awareness to the breasts (eg, running and swimming) [36]. Each of these risky behaviors can yield a number of detrimental health outcomes [25,37-40].

For many trans people who experience gender dysphoria, gender-affirming health care offers various approaches to alleviate this distress and any subsequent negative outcomes. Gender-affirming health care refers to social, behavioral, psychological, and medical interventions that support and respect an individual’s gender identity [14,15]. Medical gender-affirming health care, which includes gender-affirming surgeries, comprises interventions that help alleviate gender dysphoria in many trans people [41]. However, it is important to recognize that not all trans people pursue medical interventions, nor are all trans people who desire such interventions able to access them [9].

Gender-affirming surgeries can include “bottom” surgeries (eg, phalloplasty and vaginoplasty), facial surgeries (also known as “facial feminization” or “facial masculinization” surgeries), vocal surgery, and “top” surgeries [42]. The phrase “top surgery” is used within this study as an umbrella term for all gender-affirming chest and breast surgeries, including both chest reconstructive procedures and breast augmentation. Chest reconstruction and breast reduction involve the removal of breast tissue, sometimes with additional skin removal [43]. Breast augmentation often involves inframammary incisions to insert implants, the size of which depends on a patient’s preference and chest anatomy [43,44]. Both chest reconstructive surgeries and breast augmentation may also involve the repositioning and resizing of the nipple areolar complex [42], and chest reconstruction may include contouring to create a more masculine or gender-affirming chest shape [45]. One recent meta-analysis suggests top surgeries are the most common gender-affirming surgeries accessed by trans people [46], with 56.6% of trans people who had accessed gender-affirming surgeries having had either chest or breast procedures, compared to 35.1% having had bottom surgeries and 13.9% having had other facial or cosmetic procedures. Some studies report top surgeries as being up to twice as common as bottom surgeries [7,47,48].

Top surgery has been associated with improved physical, psychological, and social well-being, including significant improvements in quality of life [44,49-51] and improved mental health and behavioral outcomes [44,49-55]. For instance, top surgery has been associated with reductions in depression, anxiety, and suicidality, both when comparing trans people before and after surgery [51-55] and when comparing those who have and have not undergone the procedure [54]. It has also been associated with decreased gender dysphoria and dysphoria related to the chest or breasts, also known as chest dysphoria [51,52,55], as well as lowered rates of eating disorders [56]. Both adolescent and adult trans populations have reported high levels of satisfaction following top surgeries [51,52,55], with low complications and rates of regret [51,52,55]. In a meta-analysis of regret following top surgery in trans adolescents and adults (aged 13 years and older), the pooled prevalence of regret was reported as 1% [57]. Among individuals undergoing feminizing top surgeries, regret ranged from less than 1% to 2%, while for those undergoing masculinizing surgeries, regret was less than 1%; this is consistent with previous pooled estimates showing regret rates between 1% and 1.5% [58].

Nonsurgical gender-affirming interventions—such as chest binding or breast forms—are important, reversible alternatives for those unable to, or not wishing to, access top surgeries. Though temporary, these options have been shown to reduce gender dysphoria and improve mental health and quality of life [59,60]. However, nonsurgical alternatives also have important limitations. For example, extended or improper chest binding can pose significant physical health risks, including back pain, shortness of breath, chest pain, and skin irritation [61,62], and both binding and breast forms require daily application, offering only temporary relief from chest dysphoria. For these reasons, many trans people ultimately prefer and pursue top surgery for its ability to provide permanent, comprehensive management of chest dysphoria [36,63].

Although current evidence supports the use of top surgery in the management of gender dysphoria, there are several methodological limitations in the existing research. Most studies are retrospective [51,64-67], have follow-up periods of less than 1 year [68,69], do not control for concurrent gender-affirming treatments [57,70,71], and do not specifically evaluate mental health and quality-of-life outcomes following surgery [53,72,73]. Retrospective designs can be subject to bias, as participants are expected to recall presurgical functioning, while short follow-up periods cannot establish whether improvements persist or how outcomes evolve over time. The few studies with longer-term follow-up periods are retrospective with high attrition rates, introducing survivorship bias that may inflate positive outcomes and limit generalizability. While the limited prospective research demonstrates high postsurgical satisfaction (90%‐93%) [49,52] and improved mental health outcomes [52,55,74,75], these studies are constrained by small sample sizes [63,76], follow-up periods of 6 months or less [49,51,52,74], and lack of comparison or control groups [49,52,75-77]. Prospective designs with longer follow-up periods are therefore needed to accurately measure changes from baseline, identify how improvements change over time, and examine whether outcomes are sustained over the long term.

Additionally, most studies originate from the United States and Europe [51,55,65-67,78], limiting external validity for other cultures and health care systems in other countries. Different national contexts present distinct financial, cultural, and societal landscapes that influence not only access to top surgery, but also the quality and continuity of peri- and postoperative care, availability of social support, and exposure to stigma and discrimination—all factors that can shape health outcomes [79-81]. In the United States, structural stigma—including specific anti-transgender legislation and hostile political climates—has been associated with poorer mental health among trans people, independent of direct barriers to care [79,80]. While the United Kingdom offers publicly funded top surgery, long wait times have been associated with poorer mental health during the waiting period [81]. In Australia, waitlists are typically shorter; however, comprehensive public funding for top surgery is lacking, with most procedures occurring in the private sector and out-of-pocket costs ranging from AUD $4000 to AUD $18,000 (US $2844 to US $12,797) [82,83]. Collectively, these findings suggest that each country’s unique health care, legislative, and social contexts may differentially influence health outcomes following top surgery. Australian-specific research is therefore needed to understand how these contextual factors operate locally and to inform evidence-based clinical practice and policy.

An additional limitation of the current literature is the scarcity of validated tools to measure health outcomes following top surgery among trans people specifically [55,84,85]. Most studies have used measures designed for cisgender people [44,49,55,84,85], such as the BREAST-Q [86], or tools developed to assess disordered eating, such as the Body Uneasiness Test [87]. Other studies have measured health outcomes with unvalidated Likert scales [55,84,86,88,89]. However, these tools do not capture the specific experiences of trans people (such as distress arising from gender dysphoria; the unique, positive impact of gender euphoria; or the functional limitations associated with chest binding), which limits their utility in studies on gender-affirming procedures. Recent research has seen the development and early validation of trans-specific measures that show promise for future work in this space. The Olson-Kennedy Scale [36], a validated measure of chest dysphoria, addresses this gap by assessing some of the experiences central to trans people, including binding behaviors, avoidance of gendered spaces, and limitations on social participation and sexual relationships. In addition, the Gender Euphoria Scale (GES) is a novel tool designed to assess positive feelings about one’s gender [90], and the GENDER-Q [91], adapted from the BREAST-Q and the BODY-Q [92,93], is a newly developed patient-reported measure of gender-affirming care outcomes. Unlike existing instruments, the GENDER-Q also explicitly included nonbinary individuals in its validation samples, demonstrating the measure’s applicability across diverse gender identities and gender-affirming trajectories. Taken together, these developments highlight the importance of using instruments developed and validated for use with trans samples to ensure postsurgical outcomes are measured accurately and meaningfully.

Few studies on top surgery to date have included nonbinary participants [64,74,94]. This could be attributed to the misconception that nonbinary people do not wish to pursue medical gender-affirming care [95]. While nonbinary people access medical gender affirmation at lower rates than binary trans people [96,97], Australian estimates suggest that 25.1% of nonbinary people have had at least one gender-affirming surgery and 23.6% are taking steps to access gender-affirming surgeries [48]. In addition, studies suggest nonbinary people experience distinct barriers when attempting to access medical gender-affirming care, including pressure to transition to a binary gender and a lack of information on gender-affirming care specific to nonbinary gender identities [98]. Nonbinary people seeking chest masculinization procedures have also been shown to differ from binary trans people in their aesthetic preferences [94,99]. However, a recent systematic review found no studies discussing surgical techniques or outcomes in nonbinary patients undergoing chest feminization [94]. Despite these findings suggesting that nonbinary individuals have distinct surgical preferences and experiences, there have been limited studies on outcomes specific to nonbinary individuals undergoing top surgery [74]. This underscores the need to include nonbinary individuals when evaluating the effects of top surgery on the mental health and quality of life of trans people [74,100,101].

Top surgery is anticipated to improve mental health and quality of life in trans individuals and reduce the distress associated with gender dysphoria. However, few studies have specifically examined detailed mental health and behavioral outcomes following top surgery [53,72,73], and of those that have, fewer used validated instruments [84]. In addition, most studies are retrospective in design [64,66,84], have short follow-up periods [64,66,68,69], and do not account for nonbinary participants [64,68,69,74,94]. Thus, this prospective cohort study aims to fill these knowledge gaps by longitudinally evaluating the effects of top surgery on the mental health, risky behaviors, gender dysphoria, and quality of life of trans people, including nonbinary people.

We hypothesize that there will be reductions in negative mental health outcomes (ie, gender dysphoria, depression, anxiety, and suicidal thoughts and behaviors) and risky behaviors (self-harm, substance use, disordered eating, compulsive exercise, and avoidance of physical activity), and improvements in positive outcomes (ie, gender euphoria and quality of life) at 6‐8 weeks post surgery relative to baseline scores, and that these changes will be maintained at 1 year post surgery. Additionally, we hypothesize that individuals who report higher satisfaction with surgical outcomes will experience greater reductions in negative outcomes and greater improvements in positive outcomes compared to those with lower self-reported satisfaction.

We are currently conducting a prospective cohort study of trans people aged 16 years and older undergoing top surgery in Perth, Western Australia. Participants complete measures over 3 time points: within 8 weeks prior to surgery (T0), 6‐8 weeks post surgery (T1), and 1 year post surgery (T2). If a participant’s surgery is postponed by 4 or more weeks and a participant has already completed their presurgery questionnaire, they are asked to complete the presurgery questionnaire again within 8 weeks of their new surgery date. The previous presurgery questionnaire data are then disregarded. Outcomes measured include mental health, gender dysphoria, gender euphoria, and quality of life. Bespoke questions developed through community consultation are also included. Experiences accessing surgical care, including barriers and available supports, are measured at T0, while follow-up questionnaires investigate recovery from top surgery, including support received and surgical satisfaction (T1 and T2). With consent from the participant, the operating surgeon’s satisfaction with surgical outcomes is reported in a pro forma 3 months after surgery (surgT0), coinciding with the patient’s 3-month follow-up appointment. If revision surgeries are required, the operating surgeon completes additional pro formas for each added surgery (surgT1; additional time points to be added as needed). An overview of the study design is provided in Figure 1.

This study received ethics approval from the University of Western Australia Human Research Ethics Committee (2021/ET000069) in accordance with the National Statement on Ethical Conduct in Human Research (2023). Written informed consent is obtained from all participants prior to data collection via an online consent form administered through Qualtrics. For participants aged 16 to 18 years, the patient and their parent or guardian are invited to attend a videoconference or telephone call to discuss the study with the research team. If the young person is interested in participating, they and their parent or guardian are each sent a link to complete their respective consent forms online. No compensation is provided to participants for their involvement in this study.

Participant data are deidentified, with names and identifying information replaced with unique study codes. Staff from the surgeon’s office pass contact information to the research team, but the participating surgeon does not know which patients are participating until after surgery when they are asked to complete the surgeon pro forma. The surgeon does not have access to participants’ self-report questionnaire data at any stage. All data are stored on password-protected, encrypted servers accessible only to members of the research team.

The questionnaires were developed through a multistage iterative process involving community consultation and professional input. Initial item development was informed by a review of existing literature on mental health, well-being, and surgical outcomes in trans populations and broader surgical contexts. A preliminary item pool was developed and refined by the research team, with the participating surgeon specifically reviewing the surgeon pro forma to ensure clinical relevance.

A Community Advisory Group, comprising 13 trans individuals who had recently undergone or were planning to undergo top surgery, convened twice during the development of the questionnaires. The group reviewed draft items and provided feedback that was used to refine item wording, ensure questions and response options were appropriate and inclusive, ensure all relevant topics were addressed, and identify areas not adequately covered by the included validated measures. This iterative process informed the development of bespoke items to address these gaps.

The final questionnaires combine validated measures, targeted bespoke items, and open-ended questions (refer to Multimedia Appendices 1-3). Validated instruments were selected based on their psychometric properties, relevance to the study’s outcomes of interest, and applicability to trans people, including prior use with trans populations where possible. Three members of the community advisory group tested the T0 questionnaire and their feedback was incorporated across all 3 questionnaires.

There is a chance that participation in any research may cause distress, particularly when reflecting on experiences related to gender-affirming care, mental health, or discrimination. This potential risk is outlined in the participant information sheet, which all participants are asked to read prior to consenting. A risk management protocol has been developed to manage risk if participants indicate thoughts of self-harm or suicide during the questionnaires or request further support from the research team. Prior to the mental health–related section of the questionnaire, a disclaimer advises participants that their responses will remain confidential (but not anonymous). Participants are also advised that if their responses indicate a high level of risk, a member of the research team will attempt to contact them to offer assistance in accessing mental health support. Mental health and crisis support service contact details are provided before and after the mental health sections and at the end of each questionnaire.

If a participant selects a response greater than 0 (not at all) on Item 9 (“Thoughts that you would be better off dead, or of hurting yourself”) of the PHQ-9, or anything greater than (never) on Item 16 (“Do you ever feel like hurting yourself?”) of the AQoL-8D, an automated email alert is sent to the research team. A member of the research team will then contact the participant via email to offer assistance in accessing additional support. If the participant requests follow-up, a member of the research team will contact them and administer the Columbia-Suicide Severity Rating Scale [114] and implement further support strategies depending on the level of risk identified. If the participant does not respond to the initial email, a member of the research team will follow up via text message. If the participant does not respond to the text message, a second email will be sent providing a comprehensive list of mental health and crisis support services. At this stage, it will be assumed that the participant does not want assistance from the research team.

There are minor risks associated with the surgeon knowing which patients have consented to participate in the study. Participants might feel pressured to participate based on their relationship with the surgeon or alter their responses due to concerns about how these will impact their medical care. To minimize this risk, all recruitment and consent procedures will be conducted independently of the surgical setting. Participants will be informed that their surgeon will not have access to their self-reported data at any stage, that their surgeon will only become aware of their study involvement after their surgery has been completed, and that choosing not to participate will not affect their medical care.

Patient-reported data will be collected online through the University of Western Australia’s secure Qualtrics server. Surgeon-reported data from pro formas will be manually entered into a deidentified digital database. Physical data will be stored in a locked cabinet at The Kids Research Institute Australia, and all digital data will be password-protected and stored on secure servers. As the study may include participants younger than the age of 18 years, data will be retained for a minimum of 7 years following the last publication or until all participants are aged 25 years, whichever occurs later. The findings of this study will be submitted for publication in a peer-reviewed journal and may also be presented at conferences nationally (eg, Australian Professional Association for Trans Health and Australian Society of Plastic Surgeons) and internationally (eg, World Professional Association for Trans Health).

This prospective cohort study aims to extend existing research by comprehensively examining the long-term impacts of top surgery on mental health, dysphoria, and quality of life among trans people in Australia. Most existing research has been conducted in North America [49-52,54-56] and Europe [66,67,78], where health care systems differ substantially from the Australian context. Barriers to accessing top surgery vary internationally; in Australia, out-of-pocket cost is the primary barrier, yet the mental health implications of this specific access landscape remain underexplored. By collecting both quantitative and qualitative data, this study will provide Australia-specific evidence on postsurgical outcomes as well as important context regarding barriers to accessing care.

This study also addresses key methodological limitations of existing research by adopting a prospective longitudinal design, enabling direct comparison of patient-reported outcomes before and after surgery. Unlike the majority of previous research, which has used retrospective designs [51,64-67], this approach allows for more accurate assessment of changes over time and identification of specific temporal patterns. For instance, some participants could experience immediate improvements in their mental health, while others might face initial challenges, such as stress and postoperative pain, before experiencing longer-term mental health improvements. Understanding these patterns and exploring potential associations will help inform patient expectations, pre- and postoperative care, and support strategies.

An additional strength of this study is its use of validated instruments to measure patient-reported outcomes, several of which have been developed specifically for use in trans populations [36,90,93]. Using these measures should address limitations of past studies that relied on unvalidated or ad hoc measures [36,84,85,90,93], providing a more robust understanding of postsurgical outcomes. Moreover, the inclusion of nonbinary participants—a population often underrepresented in research on gender-affirming surgeries [64,74,94]—will provide novel insights into their specific preferences, experiences, and outcomes. This inclusion will also allow for direct comparison between binary and nonbinary participants, contributing to more inclusive and informed care for nonbinary people undergoing top surgery.

Several limitations concerning the proposed study should be acknowledged. First, as top surgery is inaccessible through the Australian public health system, access is currently limited to those with private health insurance or the financial means to self-fund their surgery. As a result, the study sample may not be representative of the broader trans population, specifically those who do not wish for top surgery or are unable to access it for financial or other reasons. It is likely that participants will have higher incomes or greater access to financial resources, potentially skewing results toward more favorable outcomes. For instance, a sample consisting of high-income earners might mean participants face fewer barriers, have greater access to material supports, or have better mental health overall [115-117].

Second, recruitment from a single surgical site may limit the generalizability of our findings. As the participating surgeon specializes in transverse inframammary incisions with free nipple grafting, or “double incision technique,” outcomes related to surgical satisfaction and healing may not be generalizable to other types of top surgery. Additionally, the study may overrepresent individuals seeking chest reconstructive procedures, similar to much of the existing research [118,119]. Planned expansion to additional surgical sites in the future is expected to address this limitation.

In addition, there is a risk of attrition bias in the completion of follow-up assessments. Participants with poorer mental health outcomes may be more likely to drop out between time points [120-122], which could lead to an overrepresentation of favorable experiences and an underestimation of potential challenges or negative outcomes. While studies suggest that selective attrition does not significantly bias results [123,124], we will nevertheless implement strategies to minimize disengagement. These include offering flexible completion options and sending multiple reminders to complete the follow-up questionnaires. In addition, we will continue to monitor attrition and consider implementing statistical methods, such as inverse probability weighting, if necessary.

Finally, the study follows participants for only 1 year post surgery. While this time frame is longer than that of many existing studies [68,69], it does not capture longer-term changes that may occur beyond the first year post surgery. Additionally, with only 2 follow-up periods, we may miss potential fluctuations in outcomes between these time points. The inclusion of consent to contact participants for additional follow-up questionnaires, however, allows for the possibility of longer-term follow-up in future phases of the project.

The proposed study is expected to enrich and extend our understanding of top surgery outcomes for trans people, including nonbinary people, in Australia. Findings are anticipated to have substantial implications for the provision of gender-affirming health care, offering health care professionals—including surgeons, general practitioners, and mental health clinicians—a deeper understanding of patients’ needs and evidence to guide patient-centered care. The findings also have the potential to offer trans people considering surgery a clearer understanding of the potential impacts on mental health, dysphoria, and quality of life, thereby informing and empowering their decision-making.

By expanding upon previous research demonstrating the positive impacts of top surgery, this study has the potential to inform broader policy and public health initiatives related to gender-affirming care. Through contributing robust, longitudinal data, the findings of this study may support advocacy efforts to improve access to top surgery in Australia and promote the development of inclusive, affirming health care systems. For example, we will be able to conduct a cost-utility analysis using the quality-of-life data, which will be informative for the current process of consideration of top surgery for inclusion on the Medicare Benefits Schedule by determining the value of subsidizing the cost of this surgery.

This study seeks to evaluate the impact of top surgery on trans individuals by comprehensively assessing mental health, dysphoria, and quality-of-life outcomes over time. It is expected that findings will guide improvement in surgical care and follow-up protocols, inform health care policy, and ultimately improve the quality and accessibility of care for trans people undergoing top surgery.