Abstract
Mutism in childhood and adolescence is a psychopathologically heterogeneous sign that current classifications reduce to selective mutism, an anxiety disorder, leaving subtypes associated with severe affective, psychotic, and catatonic conditions largely absent from the paediatric literature. This systematic review aims to propose and validate against the available literature an integrative six-subtype classification of mutism in childhood and adolescence — oppositional, selective/phobic, depressive, perplexed, delusional, and catatonic — characterising their neurobiological substrates, risk factors, and clinical implications. A systematic review with narrative synthesis (PRISMA 2020; SWiM guideline) searched PubMed/MEDLINE, PsycINFO, Embase, and Cochrane Library from inception to 30 April 2025; seminal textbooks (Ajuriaguerra 1970; DSM-5-TR; ICD-11) were included as foundational references, and quality was assessed using MMAT and AMSTAR-2. One hundred and fourteen records met inclusion criteria (111 empirical studies and 3 foundational texts). Each subtype showed a distinct neurobiological substrate, phenomenology, and risk profile; the selective/phobic subtype has the most robust paediatric evidence, while depressive, perplexed, and catatonic subtypes remain systematically underrecognised, and sitiophobia emerged as an extreme severity marker lacking operationalisation in current guidelines. This dimensional classification has direct implications for clinical practice, medical education, and research, and is offered as a testable tool pending prospective validation.