Sex differences modulate resilience and susceptibility to distinct stress-induced behavioral phenotypes in mice.

Chronic stress induces an allostatic load linked to neuropsychiatric disorder susceptibility, whereas allostasis recovery promotes resilience. This study evaluated responses to chronic restraint stress in adult male and female C57BL/6 mice to identify resilient and susceptible subgroups, classify susceptible phenotypes, and investigate associated oxidative alterations. Behavioral assessments were conducted on days 7, 14, 28, and 40 of the chronic restraint stress protocol (2 h/day). Data were normalized into a Z-score for depressive- and anxiety-like emotionality and validated by ROC curves to establish cut-off points for the identification of resilient and susceptible subgroups. Susceptible mice were then classified as depressive-like (DEP), anxiety-like (ANX), or depressive- and anxiety-like emotionality (DEP + ANX). Longitudinally, stress affected susceptibility in a time- and sex-dependent manner. Moreover, proportionally, up to day 28 of stress, female mice were more susceptible to DEP phenotype, whereas males were more susceptible to ANX phenotype. Stress also induced a predominance of the DEP + ANX phenotype up to day 14, shifting to a DEP phenotype predominance after 28 days. Furthermore, the DEP + ANX phenotype induced oxidative alterations predominantly in females. This work highlights that variations in sex and stress response must be considered in preclinical studies using stress as a model to induce neuropsychiatric disorders. Stratifying susceptible animals by phenotype in response to stress provides valuable insights for developing targeted translational pharmacological strategies.