IL-37 and Neuroimmune Mechanisms Relevant to Depressive and Anxiety Disorders: A Scoping Review.

Neuroimmune dysregulation and altered pro- and anti-inflammatory signaling have been implicated in selected phenotypes of depressive and anxiety disorders. Interleukin-37 (IL-37), a member of the IL-1 family, exerts anti-inflammatory effects through extracellular signaling involving IL-18Rα and IL-1R8 and intracellular interactions with SMAD3. This scoping review mapped direct and indirect evidence concerning the relevance of IL-37 to depressive and anxiety disorders. PubMed/MEDLINE was searched through 12 July 2026, supplemented by backward citation searching and reference-list checking; evidence was charted by study type, population or model, IL-37 assessment, principal findings, and level of psychiatric relevance. Thirty-two IL-37-related sources were included. Direct psychiatric evidence comprised one small cross-sectional human study and two rodent stress-model studies, in which IL-37 was assessed as one component of broader inflammatory profiles rather than as a prespecified primary biomarker or intervention target. The remaining evidence was derived from non-psychiatric inflammatory conditions, central nervous system disease models, or mechanistic studies. These findings provide hypothesis-generating biological context but do not establish psychiatric specificity, causality, biomarker validity, or therapeutic efficacy. IL-37 should therefore be considered an exploratory research variable requiring validation in well-characterized longitudinal psychiatric cohorts using standardized assays and integrated immune profiling.