Clozapine Across Treatment-Resistant Symptom Dimensions: A Conceptual Review and Transdiagnostic Rationale for Child and Adolescent Psychiatry

Clozapine is the most effective antipsychotic for treatment-resistant schizophrenia, yet in children and adolescents it remains off-label and underused, constrained by safety concerns and scarce pediatric-specific evidence. Its benefits may extend beyond any single diagnostic category to severe, treatment-resistant dimensions of psychopathology that recur across diagnoses. This review traces clozapine’s history in youth, synthesizes the current evidence, and organizes it by domains of treatment resistance: psychosis, aggression, affective symptoms, suicidality and self-directed harm, and catatonia, with sections on real-world outcomes, clinical management, and safety. Randomized controlled data are confined to treatment-resistant early-onset schizophrenia and to one small trial in conduct disorder, with the first prospective open-label trial now available in autistic youth. Elsewhere the evidence is observational and of lower certainty, although convergent for aggression, suicidality, mood, and catatonia. The strongest transdiagnostic evidence is register-based and within-individual, drawn from cohorts aged 16 years and older, and spans psychotic and affective disorders; the pediatric gap concerns study design as well as sample size. Because pharmacovigilance data show that mortality is not concentrated in the hematological domain, safe use requires surveillance beyond blood counts, therapeutic drug monitoring, and safeguards over drug supply when suicide risk is present. Viewing clozapine as a treatment option defined by symptom severity and refractoriness may support rational use in severely ill youth, but the proposal remains preliminary: a conceptual framework that requires prospective, dimensionally designed pediatric studies. Clozapine’s potential transdiagnostic anti-suicidal effect merits priority investigation, given that suicide is a leading cause of death in adolescence.