Summary of findings: The aim of this study attempted to identify sex specific responses to prolonged stress by placing a cohort of male and female mice to a series of sub-chronic variable stress (SCVS). In particular, the tail suspension stressor (TSS) functioned as the most indicative of differences in stress response. Particularly in Figure 2, a comparison of immobility score and immobility bouts were seen to have an observable difference in stress response between first and second exposures. Initial findings from the first exposure concluded that sex differences did not influence immobility score/bouts, but female mice experienced increased stress relative to males.

Major strengths: Standard SCVS methods typically include forced swimming in which mice are placed in water for 12 minutes to measure passive or active coping strategies. In this study, tail suspension was used as an alternative method to the swim test to measure both immobility bouts and total time immobile rather than only time spent immobile. Additionally, the TSS identified key sexed-based differences between individual time points. Thus identifying female coping strategies as being active compared to the males, with females tending to have lower rates of immobility. Cumulatively, these findings are significant to the field, elucidating sex-based differences in how the mice respond to repeated stressors; however, there are a few caveats to these claims.

Major weaknesses: Baseline responses to the elevated plus maze, which is used to assess the mice’s avoidance behavior, are not presented. Additionally, inclusion of when the elevated plus maze was performed relative to the SCVS would help contextualize how the mice respond while stressed. The regression lines in Figure 4 should not extend past the range of the data points, as this easily leads to overinterpretation of the data. The gender of the mice handler(s) should be noted since it is known that there is a significant increase in the mice’s overall stress/anxiety levels with male handlers. I am personally unfamiliar with the SCVS paradigm, but would quantification of the other stressors in the SCVS be possible? An orthogonal validation of coping strategy predicting avoidance behavior would greatly strengthen the claims.

Minor concerns: The heatmap in Figure 5 includes multiple redundant variables where the first 10 minutes, average, and slope are all inherently linked. The heatmap is also symmetrical, so removal of one half may improve readability. Figure 6 identifies the largest sex-based differences in responses - preference for tail climbing during tail suspension; however, it is the final figure of the paper. An earlier inclusion would help with the overall flow of the paper