From Diagnosis by Accumulation to Diagnosis by Layers: Cognitive Psychiatry and Iatrogenic Risk in an Adolescent with Autism Spectrum Disorder: A Case Report and Narrative Review

Background: Adolescents with autism spectrum disorder (ASD) may show overlapping behavioural descriptions arising from neurodevelopmental features, psychiatric syndromes, environmental stressors and medication effects. Objective: To illustrate a layered psychiatric formulation using the clinical course of an adolescent with ASD, self-harm, restrictive eating, atypical experiences and prolonged psychopharmacological exposure. Methods: Clinical material supplied by the treating team was synthesised as a case report, with a complementary structured narrative review of literature on diagnostic overlap, pharmacotherapy, puberty, safety and feeding. The main PubMed/MEDLINE search covered January 2023 to September 2026, with a subsequent targeted update; evidence selection was purposive rather than systematic. Case Presentation: A 16-year-old adolescent experienced school and adaptive difficulties, sensory sensitivities, food restriction with occasional self-induced vomiting, self-injury and suicidal ideation. Clinical records described sequential exposure to several psychotropic agents. A reduction in lithium dose from 450 to 300 mg/day during the September 2026 admission was followed by improvement in reported hygiene, food variety and family interaction, but later by distress and an urge to self-harm. Co-occurring psychotherapy, environmental changes and uncertain clinical measurements prevent causal attribution. Discussion: The proposed eight-layer framework considers constitutional traits, temperament, neurodevelopment and cognition, psychodynamics, relationships and environment, superimposed syndromes, somatic factors and treatment effects. The concept is heuristic, not a validated diagnostic instrument. Feeding symptoms warrant assessment of sensory selectivity, body-image concerns, compensatory behaviours and nutritional consequences. Evidence associating adverse childhood experiences with neuroimaging measures in autistic samples is relevant context but does not substitute for individual assessment. Conclusion: Longitudinal, risk-sensitive formulation may help identify competing explanations and measurable intervention targets. The clinical sequence does not establish that medication, family circumstances or any single intervention caused the observed outcomes.