Prader-Willi syndrome as a neurogenetic model for psychosis and obsessive-compulsive disorder: A review of clinical, behavioral, and biological insights.

Prader-Willi syndrome (PWS) is a complex neurodevelopmental disorder classically defined by hyperphagia and obesity. However, its profound psychiatric phenotype offers a unique genetic framework for understanding major mental illnesses. This review positions PWS as a potentially informative biological model for psychosis and obsessive-compulsive disorder (OCD), bridging the gap between 15q11-q13 imprinting defects and neural circuit dysfunction. We synthesize evidence demonstrating that psychosis in PWS is not a uniform trait but is disproportionately linked to the maternal uniparental disomy (mUPD) subtype. This genotype-phenotype correlation suggests that overexpression of maternally imprinted genes and loss of paternal expression disrupt cortical excitatory-inhibitory balance, resembling the "schizophrenia-bipolar" genomic architecture. Furthermore, synthesized evidence characterizes the repetitive, ritualistic behaviors in PWS not merely as behavioral challenges, but as a developmentally arrested OCD-spectrum phenotype driven by distinct serotonergic-oxytocinergic imbalances and hypothalamic-limbic dysconnectivity. Mechanistic insights from preclinical models of MAGEL2, SNORD116, and NDN deficiency are integrated with clinical findings to highlight shared neurobiological substrates. Finally, we outline a roadmap for precision psychiatry in PWS, emphasizing the necessity of pharmacogenomics in antipsychotic management and the potential of targeted circuit-based therapeutics. By deconstructing the psychiatric comorbidities of PWS, we provide a framework for translating genomic architecture into mechanistic understanding and targeted treatment for complex neuropsychiatric disorders.