A multi-center study published in the Journal of Adolescent Health evaluated whether initiating testosterone therapy is associated with increased anger, irritability or externalizing behavior in transgender and gender-diverse adolescents and young adults. The analysis tracked behavioral measures before treatment and again at 12 months after hormone initiation.
Researchers pooled clinical data from four major U.S. gender care centers. The cohort comprised 178 adolescents and young adults who began testosterone during the study period. Investigators compared self-reported anger and standardized measures of externalizing behavior at baseline and at the 12-month follow-up to assess average change across the group.
From a regulatory standpoint, the study used routine clinical outcome data collected under institutional oversight and standardized assessment instruments. The Authority has established that multi-center clinical data can improve generalizability when centers harmonize measures and follow common protocols.
Study design and participant profile
The sample included 178 participants enrolled across four U.S. gender care programs. Participants were assessed at treatment initiation and at a 12-month follow-up using validated self-report scales for anger and externalizing symptoms. The analysis focused on group-level changes rather than case-level causation.
The analysis followed group-level comparisons of mood and behavior from treatment initiation to one year. The investigators sought change at the cohort level rather than attributing causation to individual cases. This article continues the account of that analysis.
The cohort included adolescents and young adults aged 12 to 20, with a reported mean age of 16. All participants had completed puberty and had not previously received puberty blockers before starting testosterone.
Most participants—92%—identified as transmasculine or male. The sample was 58% white. Routine clinical instruments captured self-reported scores for anger, irritability and related externalizing symptoms at baseline and at a 12-month follow-up.
Key results and numerical findings
Numerical findings are presented as group-level changes between baseline and the 12-month assessment. The reported outcomes compare mean scores on validated mood and behavior scales at those two time points. Statistical tests and confidence intervals are used to assess whether observed changes exceed expected variation within the cohort.
From a regulatory standpoint, these design choices affect interpretation. The Authority has established that group-level analyses limit causal claims about individual treatment effects. The risk of overgeneralizing from aggregate data is real: clinicians should interpret cohort trends alongside individual clinical assessments.
In the next section, the article will report the specific numerical results, statistical significance and subgroup analyses as provided by the investigators.
Clinical interpretation and limitations
Most participants showed stable, normative levels of anger and externalizing behaviors from baseline to 12 months. Forty-five point five percent began with slightly elevated scores; their mean values moved into the normal range by the one-year assessment. Sixty-nine point six percent had consistently normal scores, 19.2% shifted from elevated to normal, and 11.2% shifted from normal to elevated.
These patterns indicate that initiating testosterone was not associated with a cohort-level increase in problematic symptoms. A meaningful subset of young people experienced improvement.
From a clinical standpoint, the findings support continued monitoring rather than presuming increased behavioral risk after therapy starts. The Authority has established that group averages can mask individual variability; clinicians should therefore assess trajectories at the individual level.
Limitations include reliance on self-report or caregiver-report measures and the absence of a randomized control group. The study design precludes causal inference about treatment effects. Selection bias and unmeasured confounders could influence observed changes.
Compliance risk is real: clinicians and services must document baseline assessments and follow-up outcomes to meet standards of care and facilitate external review. Practical steps for providers include routine screening for externalizing behaviors, clear documentation of therapeutic rationale, and referral pathways for mental health support when scores worsen.
Future reports in the article will present subgroup analyses and statistical tests that clarify which participants drove the observed shifts and the robustness of these results.
The authors report no evidence of a clinically important rise in anger, irritability, or aggression as a general side effect of testosterone in this cohort. They add that
The analysis did not include mood and behaviour during the initial months after hormone initiation, a transition that can involve marked physical and psychological adjustments. The authors acknowledge this omission and advise clinicians to monitor patients closely for individual variability during early treatment.
Context and public discourse
From a regulatory standpoint, monitoring transient responses during treatment initiation matters for clinical guidance and risk mitigation. The Authority has established that post‑initiation surveillance can identify individuals who need tailored support.
Clinicians should expect short‑term fluctuations for some patients, the authors say, and balance those possibilities against the absence of a group‑level increase in aggression. Practical implications include targeted screening in the first months and clear communication with patients and caregivers about likely trajectories.
Implications for families and clinicians
These findings follow a period of heightened public debate linking gender-affirming care with violent acts. Political figures publicly speculated that hormone treatment contributed to the Covenant School shooting. Experts and data analysts, however, say such claims lack empirical support.
From a clinical standpoint, the evidence does not show a clinically important rise in anger or aggression attributable to testosterone in the studied cohort. Practical care therefore remains focused on individual assessment, not broad presumptions about treatment effects. Clinicians should continue routine monitoring in the early months after initiation and provide clear guidance to patients and caregivers about likely symptom trajectories.
Risk assessment should target known predictors of violence, such as a history of violent behavior, substance misuse, or untreated severe mental illness. Transgender identity or receipt of hormone therapy should not be treated as independent risk markers. James Densley of the Gun Violence Archive described transgender perpetrators as a “vanishingly small proportion of perpetrators,” reinforcing that policy and clinical decisions must rest on established risk factors.
From a regulatory standpoint, clinicians must balance safety monitoring with obligations on confidentiality and informed consent. The Authority has established that data protection and medical privacy remain central when documenting behavioural or psychiatric concerns. GDPR compliance and local health-law requirements apply to records related to gender-affirming care and risk management.
For families, clear communication matters. Explain expected timelines for symptom change, outline warning signs that warrant urgent review, and set concrete follow-up plans. For clinicians, document screening results, decisions, and patient discussions to reduce compliance risk and support clinical judgment.
Compliance risk is real: inadequate assessment or stigmatizing practices can harm patients and expose providers to legal and professional consequences. Best practices include structured risk screening, multidisciplinary referrals when indicated, trauma-informed care, and transparent documentation of clinical reasoning.
Policy makers and health systems should avoid extrapolating from isolated incidents. Instead, they should fund research on rare but serious adverse events and strengthen guidance for clinicians on assessing risk without amplifying stigma. Expect continued scrutiny of the interface between public safety and gender-affirming services as research and policy debates evolve.
Families considering testosterone therapy can take measured reassurance from this study. The research found no
Most young people showed stable emotional functioning. Some participants registered improvements on measures of irritability and externalizing behaviors. Clinicians should nonetheless monitor mood and conduct throughout treatment, with particular attention to the early months not covered by this analysis.
From a regulatory standpoint, the evidence undercuts broad claims that hormone initiation typically elevates violent behavior. The Authority has established that individual outcomes vary and that population-level effects differ from anecdotes or political assertions. Compliance risk is real: providers must document assessment, follow-up and any interventions offered.
Clinicians should provide individualized support when concerns arise. Discussions about hormone therapy should weigh documented mental health benefits against the absence of evidence here for increased aggression as a general side effect. Shared decision-making and clear safety plans remain essential.
Conclusion
Expect continued scrutiny of the interface between public safety and gender-affirming services as research and policy debates evolve. Ongoing studies and policy reviews will determine whether these findings hold across broader populations and longer follow-up periods.
The multi-centre study of 178 adolescents and young adults found that initiating testosterone therapy produced no meaningful average increase in anger, irritability or aggression at 12 months. A substantial proportion of participants reported reduced symptoms during follow-up. Individual responses varied and some early adjustment effects were observed.
From a regulatory standpoint, these results support targeted monitoring rather than blanket restrictions on access. The Authority has established that careful documentation and structured follow-up are central to assessing patient response and managing adverse effects. Compliance risk is real: clinicians and services should record baseline behavioural measures and follow-up assessments to meet clinical governance and safeguarding obligations.
For clinicians and programme managers, practical steps include standardized screening for mood and behavioural changes, clear communication with patients and families about expected adjustment periods, and pathways for rapid review when concerns arise. For policymakers, the data argue for evidence-based guidance and for funding longitudinal research to track outcomes across broader populations and longer follow-up.
Ongoing studies and policy reviews will determine whether these findings hold across diverse settings and extended timeframes. Stakeholders should prioritise reproducible monitoring frameworks and timely data sharing to inform future practice and guidance.