The evidence base for psychological benefits of GnRHA for adolescents with gender dysphoria (GD) was deemed “low quality” by the UK National Institute of Health and Care Excellence. Limitations identified include inattention to clinical importance of findings. This secondary analysis of UK clinical study data uses Reliable and Clinically Significant Change approaches to address this gap. The original uncontrolled study collected data within a specialist GD service. Participants were 44 12–15-year-olds with GD. Puberty was suppressed using “triptorelin”; participants were followed-up for 36 months. Secondary analysis used data from parent-report Child Behavior Checklists and Youth Self-Report forms. Reliable change results: 15–34% of participants reliably deteriorated depending on the subscale, time point and parent versus child report. Clinically significant change results: 27–58% were in the borderline (subclinical) or clinical range at baseline (depending on subscale and parent or child report). Rates of clinically significant change ranged from 0 to 35%, decreasing over time toward zero on both self-report and parent-report. The approach offers an established complementary method to analyze individual level change and to examine who might benefit or otherwise from treatment in a field where research designs have been challenged by lack of control groups and low sample sizes.