Results Summary

What was the research about?

People who are transgender have a gender identity that differs from the male or female sex assigned to them at birth. Some transgender people get gender-affirming therapies to change their bodies to match their gender identity. Examples of gender-affirming therapies include surgery or taking hormones such as estrogen or testosterone.

The research team wanted to learn about health outcomes for transgender people. To do this, the team compared certain health measures among people who are transgender with the same measures among people who aren’t transgender. The study also looked at health outcomes for transgender people who did and didn’t receive gender-affirming therapies.

What were the results?

  • Mental health. Nearly all mental health conditions the research team looked at, such as depression, were more common among transgender people than people who aren’t transgender. Self-harm and thoughts about suicide were more common among transgender youth ages 10 to 17 years than nontransgender youth of the same age.
  • Cancers. Compared with men who aren’t transgender, transgender women had a lower risk of prostate cancer and a higher risk of cancers that arise from endocrine glands, such as thyroid cancer.
  • Blood clots and strokes. Transgender women who received estrogen had a higher risk of blood clots and strokes compared with men and women who aren’t transgender. Their risk for blood clots and strokes increased over time.
  • Body image. Transgender people who received more gender-affirming therapies reported that they felt better about how their bodies looked and how other people saw them compared with transgender people who received fewer or no therapies.

Who was in the study?

The research team looked at health records for 6,459 transgender people and 127,668 nontransgender people. All were members of three Kaiser Permanente health systems in Georgia and California. In addition, 697 transgender members took a survey.

What did the research team do?

Using health records for transgender and nontransgender people from three health systems over 10 years, the team compared the risk of blood clots or strokes. The team also looked at other health outcomes, such as cancer and mental health conditions.

The team sent a survey to transgender people whose health records showed that they had received gender-affirming therapies. The survey asked transgender people about the therapies they received. It also asked how they felt about the way their bodies looked after receiving any therapies.

A group of transgender people, advocates, doctors, and health system staff worked with the research team during the study.

What were the limits of the study?

This study looked at records from patients in three health systems in two states. Results may be different for patients in other health systems or for people without health insurance. The research team can’t say for sure that the risks for blood clots and strokes found among transgender patients in the study are a result of hormone therapy. Other health problems may have led to the blood clots and strokes.

Future research could look at other health benefits and risks of gender-affirming therapies for transgender patients.

How can people use the results?

These results can help transgender people who get gender-affirming therapies and their doctors be more aware of possible health problems, such as blood clots or strokes. Doctors may also want to ask transgender patients about possible mental health needs. Transgender women and their doctors may also want to be on the lookout for thyroid and some other cancers.

Final Research Report

View this project's final research report.

More to Explore...


New Evidence about Transgender Women Receiving Hormone Therapy
In this guest blog post, the principal investigator and a stakeholder partner discuss the findings of the study, which they reported in an Annals of Internal Medicine August 2018 article, and what additional research could help transgender people make informed decisions about their health.

Related PCORI-Funded Supplemental Research Study

Stroke and Blood Clot Risk in Transgender Women Taking Hormones

Journal Citations

Article Highlight: This study examined the largest cohort of transgender people in research to date. The researchers reported in Annals of Internal Medicine that transgender women who receive estrogen treatments may face a higher risk for stroke and dangerous blood clots than previously thought. In a guest blog post, the project lead and a stakeholder partner discuss the findings and what additional research could help transgender people make informed decisions about their health.

Related Journal Citations

Peer-Review Summary

Peer review of PCORI-funded research helps make sure the report presents complete, balanced, and useful information about the research. It also confirms that the research has followed PCORI’s Methodology Standards. During peer review, experts who were not members of the research team read a draft report of the research. These experts may include a scientist focused on the research topic, a specialist in research methods, a patient or caregiver, and a healthcare professional. Reviewers do not have conflicts of interest with the study.

The peer reviewers point out where the draft report may need revision. For example, they may suggest ways to improve how the research team analyzed its results or reported its conclusions. Learn more about PCORI’s peer-review process here.

In response to peer review, the PI made changes including

  • Specifying in the abstract that although there was increased risk of venous thromboembolism (VTE) and ischemic stroke (IS) after 6 years of estrogen therapy for transgender females compared to cisgender males, the overall rate of these events was relatively low, with a wide distribution in the risk estimates.
  • Expanding the description of the difficulties that the researchers experienced in completing the portion of the study within the Veterans’ Administration (VA) system. Reviewers gave varied advice about how to deal with this part of the study, and the researchers felt it was important, especially since this was part of the original protocol, to present the VA findings and their insights into dealing with difficulties of data collection.
  • Removing the presentation of analyses and results associated with a within-group analysis among transgender females based on when they started hormone therapy. The researchers found that using the hormone therapy as a basis for inclusion in the analysis, and then also differentiating within the group by when patients received the therapy, led to concerns about the complexity and the validity of those analyses.
  • Acknowledging in the Discussion that the transgender population captured in the insured cohort used in this study may not reflect the transgender population of the United States, particularly in relation to income and insurance access. This limited the generalizability of the findings.

Finally, reviewers acknowledged that a key strength of this study was the incorporation of both risks and benefits of gender affirmation care in their study. Per reviewers’ request, the researchers expanded the discussion of the benefits of such care in the report.

Conflict of Interest Disclosures

Project Information

Michael Goodman, MD, MPH
Emory University
Comparative Risks and Benefits of Gender Reassignment Therapies

Key Dates

May 2013
April 2018

Study Registration Information


Has Results
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Health Conditions Health Conditions These are the broad terms we use to categorize our funded research studies; specific diseases or conditions are included within the appropriate larger category. Note: not all of our funded projects focus on a single disease or condition; some touch on multiple diseases or conditions, research methods, or broader health system interventions. Such projects won’t be listed by a primary disease/condition and so won’t appear if you use this filter tool to find them. View Glossary
Populations Populations PCORI is interested in research that seeks to better understand how different clinical and health system options work for different people. These populations are frequently studied in our portfolio or identified as being of interest by our stakeholders. View Glossary
Intervention Strategy Intervention Strategies PCORI funds comparative clinical effectiveness research (CER) studies that compare two or more options or approaches to health care, or that compare different ways of delivering or receiving care. View Glossary
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Last updated: August 15, 2023