Resilience across time: Longitudinal invariance of the Brief Resilience Scale in French students

Abstract Background As resilience is increasingly understood as a dynamic and modifiable process rather than a fixed trait, assessing whether self-reported changes reflect genuine growth or internal shifts in perception - known as response shift - is essential for accurate longitudinal measurement. This study examined whether such an effect influenced longitudinal assessments of resilience in a French student population during the COVID-19 pandemic. Methods This psychometric analysis used data from the PIMS2-SPE longitudinal study (‘Feelings and psychological impact of the COVID-19 epidemic on students in the Grand Est area’), conducted from April 2021 to December 2022. Resilience was assessed using the French version of the Brief Resilience Scale (BRS), a self-report instrument measuring the ability to bounce back after a stressful event. To detect potential response shift effects, we applied the ROSALI-RMT algorithm, which is based on Oort's procedure and grounded in Rasch Measurement Theory. Results The analysis included 920 university students who completed the survey at both Time 0 and Time 1, providing a sufficiently powered sample for longitudinal psychometric analysis. The BRS demonstrated longitudinal measurement invariance, indicating it consistently measured the same construct across time. A slight but significant increase in resilience was observed (time effect = 0.22, p < 0.0001), with no evidence of response shift, suggesting that improvements were genuine rather than artifacts of internal recalibration. Conclusions These findings support the validity of the BRS as a robust tool for tracking changes in resilience over time. This reinforces its utility for both mental health monitoring and evaluating the effectiveness of health promotion interventions aimed at fostering psychological resilience in student populations. Key messages • The Brief Resilience Scale demonstrated stable measurement over time, supporting its use in monitoring resilience in student populations for public mental health strategies. • Observed increases in resilience reflect true change, not response shift, highlighting the scale's value in evaluating health promotion efforts targeting young adults.