Faculty Psychologist in Center for Transyouth Health and Development
Assistant Professor of Clinical Pediatrics, Keck School of Medicine of USC
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Marco A. Hidalgo, PhD, is a clinical-child and adolescent psychologist and Assistant Professor of Clinical Pediatrics at USC's Keck School of Medicine. As a faculty member in the Center for Transyouth Health and Development at Children's Hospital Los Angeles (CHLA), Dr. Hidalgo splits his time between conducting psychotherapy and research.

Dr. Hidalgo joined the CHLA/USC faculty in 2018, after relocating from Lurie Children's Hospital/Northwestern University Feinberg School of Medicine. In 2013, while faculty at Lurie Children's, Dr. Hidalgo co-established the nationally-renowned Gender and Sex Development Program (GSDP)— the Midwest's largest pediatric subspecialty program for transgender/gender-expansive children, adolescents, young adults and their families. The GSDP was profiled on the acclaimed 2015 PBS' Frontline episode "Growing Up Trans."

In his clinical work, Dr. Hidalgo’s practice is exclusively focused on children, adolescents and young adults (up to age 25) who are of gender minority experience (i.e., transgender, gender-expansive, gender non-binary). In individual and family therapy, he integrates evidence-based approaches to treat emotion and behavior problems related to depression, anxiety, traumatic stress conditions, and gender dysphoria.

Dr. Hidalgo’s research focuses exclusively on sexual and gender minority individuals, primarily youth and young adults. His research examines clinical and psychosocial mechanisms that foster wellbeing, and his more applied research focuses on developing and evaluating various modalities of HIV prevention intervention (e.g., group-based and mHealth). He is currently Principal Investigator on a 5-year NIH study examining gender development and mental health among pre-pubescent transgender/gender-nonconforming children. Dr. Hidalgo is Co-Investigator on 5 additional NIH-funded studies, including a ground-breaking observational study investigating the impact of early medical treatment in transgender youth who seek care in Los Angeles, Boston, Chicago and San Francisco (PI: Johanna Olson-Kennedy).

Clinical Interests

Gender-expansive/transgender children, adolescents and young adults


Medical School: 

DePaul University (clinical psychology)


Alexian Bros. Behavioral Health Hospital


Harvard Medical School/Cambridge Health Alliance


Professional Memberships: 

Society of Clinical-child and Adolescent Psychology (APA Div 53); Society for the Psychology of Sexual Orientation and Gender Diversity (APA Div 44); World Professional Association for Transgender Health (WPATH)


  1. A Longitudinal Study of Gender Nonconformity in Prepubescent Children
    NIH R01HD097122 Mar 21, 2019 - Feb 29, 2024
    Role: Principal Investigator
  2. Promoting Safe and Supportive Environments for Local Educational Agencies Providing School-based HIV/STD Prevention
    CDC NU87PS004362-01-00 Aug 1, 2018-July 31, 2023
    Role: Co-Investigator
  3. Mobile Adaptation and Testing of a Uniquely Targeted HIV Intervention for Young Transgender Women
    NIH R56MH113684 Sep 21, 2018 - Sep 20, 2019
    Role: Co-Investigator
  4. Y2Prevent: Preventing Drug Use and HIV through Empowerment, Social Support and Mentorship
    NIH/NIDA R34DA044106 Aug 15, 2018 - Jul 31, 2021
    Role: Co-Investigator
  5. A Pragmatic Clinical Trial of MyPEEPS Mobile to Improve HIV prevention Behaviors in Diverse Adolescent MSM
    NIH U01MD011279 Sep 1, 2016 - Apr 30, 2021
    Role: Co-Investigator
  6. Young Men of Color Who Have Sex with Men Cohort Study
    NIH/NIDA U01DA036926 Aug 15, 2015 - Jul 31, 2020
    Role: Co-Investigator
  7. The Impact of Early Medical Treatment in Transgender Youth
    NIH/NICHD R01HD082554 Aug 1, 2015 - Jun 30, 2020
    Role: Co-Investigator

Other Information


Hidalgo MA, Chen D. Experiences of Gender Minority Stress in Cisgender Parents of Transgender/Gender-expansive Prepubertal Children: A Qualitative Study. Journal of Family Issues. In Press.

Chodzen G, Hidalgo MA, Chen D, Garofalo R. Minority stress factors associated with depression and anxiety among transgender and gender-nonconforming youth. Journal of Adolescent Health. In Press.

Hidalgo, MA, Suarez N, Garofalo R, Hoehnle S, Thai J, Mimiaga MJ, Brown E, Sullivan P, Bratcher A, Wimbly T, Stephenson R. Clinically Significant Depressive Symptoms among a Diverse Sample of Same-Sex Male Couples in Atlanta, Boston, and Chicago: An Analysis of Individual- and Dyadic-level Factors. Journal of Gay and Lesbian Mental Health, 22(4); 327-347; 2018.

Schnall R, Kuhns L, Hidalgo MA, Hirschfield S, Pearson C, Radix A, Belkind U, Bruce J, Batey DS, Garofalo R. Development of MyPEEPS Mobile: A behavioral health intervention for young men. Studies in Health Technology and Informatics. 250 (31), 2018.

Garthe RC, Hidalgo MA, Hereth J, Garofalo R, Reisner S, Mimiaga MJ, Kuhns L. Prevalence and risk correlates of intimate partner violence among a multi-site cohort of young transgender women. LGBT Health, 5(6), 333-340; 2018.

Schnall R, Kuhns L, Hidalgo MA, Powell D, Thai J, Hirshfield S, …Garofalo R. Adaption of a group-based, HIV risk reduction Intervention to a mobile app for young sexual minority men. AIDS Education and Prevention, 30(6), 2018.

Hidalgo MA, Chen D, Garofalo R, Forbes C. Perceived Parental Attitudes of Gender Expansiveness: Development and Preliminary Factor Structure of a Self-report Youth Questionnaire. Transgender Health, 2(1), 180-187; 2017.

Chen D, Hidalgo MA, Garofalo R. Parental Perceptions of Emotional and Behavioral Difficulties among Prepubertal Gender-nonconforming Children. Clinical Practice in Pediatric Psychology, 5(4), 342-352; 2017.

Kolbuck VD, Chen D, Hidalgo MA, Chodzen G, Garofalo R. Parental responses to children’s gender-nonconforming behavior: A qualitative analysis. Perspectives, 2(2), 3-29; 2017.

Chen D, Hidalgo MA, Leibowitz S, Leininger J, Simons L, Finlayson C, et al. Multidisciplinary care for gender-diverse youth: A narrative review and unique model of gender-affirming care. Transgender Health. 1(1):117-23, 2016.

Bird JDP, LaSala MC, Hidalgo MA, Kuhns LM, Garofalo R. “I had to go to the streets to get love”: Pathways from parental rejection to HIV risk among young gay and bisexual men. . Journal of homosexuality.1-22, 2016.

Hidalgo MA, Kuhns LM, Kwon S, Mustanski B, Garofalo R. The impact of childhood gender expression on childhood sexual abuse and psychopathology among young men who have sex with men. Child Abuse & Neglect. 46:103-12, 2015. 

Hidalgo MA, Kuhns LM, L. HA, Mustanski B, Garofalo R. The MyPEEPS randomized controlled trial: A pilot of preliminary efficacy, feasibility, and acceptability of a group-level, HIV-risk reduction intervention for young men who have sex with men. Archives of Sexual Behavior. 44(2):475-85, 2014.

Simons LK, Leibowitz SF, Hidalgo MA. Understanding gender variance in children and adolescents. Pediatric annals. 43(6):e126-31, 2014.

Hidalgo MA, Ehrensaft D, Tishelman AC, Clark LF, Garofalo R, Rosenthal SM, et al. The gender affirmative model: What we know and what we aim to learn. Human Development. 56(5):285-90, 2013.

Hidalgo MA, Cotten C, Johnson AK, Kuhns L, Garofalo R. “Yes, I am more than just that”: Gay/bisexual young men residing in the US discuss the influence of minority stress on their sexual risk behavior prior to HIV infection. International Journal of Sexual Health. 25(4):291-304, 2013. 

Research Interests: 

Mental health, gender development, and wellness in gender-expansive/transgender children, adolescents and young adults; HIV prevention intervention for sexual and gender minority youth and young adults

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