Ipseity-Disturbance and the Nature of Self-Disorder in Schizophrenia: Clarifying Conceptual and Empirical Foundations (a Constructive Reply to Feyaerts and Sass)

Self-disorders (SDs) have emerged as a clinically salient and empirically validated phenotype within the schizophrenia spectrum, characterized by their early onset, relative temporal stability, and marked discriminative power.1 Their presence in childhood and adolescence often precedes the crystallization of formal psychosis, offering a unique window for early identification, differential diagnosis, and targeted intervention.2,3 Beyond their role as a developmental marker, SDs (and their clinical-conceptual predecessor proxy construct, ie, basic symptoms)4 contribute meaningfully to symptom-generating trajectories, prognostic stratification, and personalized treatment approaches. This clinical relevance has been substantiated by nearly 3 decades of clinical research, culminating in a coherent body of evidence and meta-analytic synthesis. It was from this developmental-clinical standpoint that our article5 sought to extend the conceptual horizon of the ipseity-disturbance model (IDM),1 rather than to oppose it. Specifically, we proposed that integrating SDs within a broader empirical and developmental framework would enhance—not diminish—the IDM’s clinical and explanatory power.