Reduced contagious yawning in psychiatric disorders: a systematic review of potential social-cognitive mechanisms.

Introduction: Contagious yawning has been proposed to reflect multiple aspects of social cognition, including empathy, emotional contagion, self-processing, Theory of Mind (ToM), and action observation mechanisms such as the human mirror neuron system (hMNS). However, its underlying mechanisms remain debated, with evidence suggesting additional roles for social attention, gaze allocation, social motivation, and neurobiological factors. This systematic review examined evidence for reduced contagious yawning in Autism Spectrum Disorder (ASD), schizophrenia-spectrum disorders, and psychopathic traits, and evaluated potential underlying mechanisms. Methods: PubMed, PsycINFO, and Scopus were systematically searched for clinical and mechanistic studies of contagious yawning in psychiatric and healthy populations. Studies were screened using predefined eligibility criteria, and risk of bias was assessed using design-specific Joanna Briggs Institute (JBI) critical appraisal tools. Twenty-three studies met the inclusion criteria. Results: Reduced contagious yawning was reported in ASD, psychopathic traits, and schizophrenia-spectrum disorders, although findings varied across conditions. In ASD, reduced contagious yawning was associated with social attention, gaze allocation, oxytocin-related processes, and broader social-cognitive differences. In psychopathic traits, evidence more consistently implicated affective-interpersonal traits and reduced emotional responsiveness. Evidence for schizophrenia-spectrum disorders was more limited, with proposed mechanisms including impairments in social cognition, ToM, negative symptoms, and possible medication effects. Neuroimaging and electrophysiological findings implicate brain systems involved in social cognition, self-processing, and action observation, although the specific role of the hMNS remains uncertain. Discussion: Reduced contagious yawning may reflect altered social-cognitive processing rather than empathy alone, with contributing mechanisms differing across psychiatric conditions. Interpretation is limited by small sample sizes, methodological heterogeneity, and variation in study design. Further well-powered studies are needed to clarify its neurobiological basis and clinical significance.