Coordinated epigenetic dysregulation of CNR1 and FAAH genes drives endocannabinoid system dysfunction in anorexia nervosa

Background: Anorexia nervosa (AN) is a severe psychiatric disorder with limited biomarkers for diagnosis and treatment monitoring. We investigated endocannabinoid system (ECS) dysregulation in AN through integrated epigenetic and genetic analysis of saliva. Methods: We analyzed DNA methylation patterns of cannabinoid receptor 1 (CNR1) and fatty acid amide hydrolase (FAAH) genes, characterized genetic polymorphisms, and quantified expression of exosomal microRNAs targeting these genes in AN patients versus healthy controls. Results: We discovered a novel bidirectional epigenetic dysregulation of the ECS: CNR1 promoter hypermethylation coupled with FAAH promoter hypomethylation. This dual-target mechanism systematically impairs endocannabinoid signaling by simultaneously reducing receptor availability while increasing endocannabinoid degradation. Compensatory miRNA responses (upregulated miR-342-3p, miR-23b-3p targeting CNR1; upregulated miR-4505, miR-1275 targeting FAAH) revealed dynamic regulatory attempts to counterbalance these primary epigenetic changes. This convergent pathway dysfunction demonstrates how multiple molecular mechanisms work in concert to dysregulate appetite regulation in AN. Combined biomarker panels showed superior diagnostic precision compared to individual markers. Conclusions: Our findings establish this bidirectional epigenetic dysregulation as a central mechanism underlying ECS dysfunction in AN, providing mechanistic insights that identify novel therapeutic targets and advance precision medicine approaches for this challenging disorder.