Limitations
Obviously, the study is not without its limitations. The first limitation is its modest sample size. According to sensitivity analyses, the resulting sample has allowed to attain sufficient power (.80) for small to medium-sized effects of the intervention (ηSecond, the sample was not representative and heterogeneous with respect to employment status and age. Also, the prevalence of female participants did not allow us to explore the gender differences in the intervention outcomes that have been reported earlier [Third, the lack of proper randomization resulted in non-equivalent groups. Nevertheless, the use of a pre-test/post-test research design has allowed us to control for baseline differences in psychological variables. Randomization would have meant withholding the possibility to obtain psychological support from some people who may have needed it most during the very beginning of the lockdown. This is why we opted to form the intervention group on a first-come first-served basis until the maximum size of the group the facilitators could accommodate was reached. In the end, all the study participants had the opportunity to benefit from the intervention.Fourth, at the time when the study was conceived, we were not aware of the existence of any validated French versions of brief instruments to measure resilience, such as the BRS-F [Finally, the absence of a placebo or an alternative intervention does not allow to rule out participant expectation effects and the absence of a passive control group did not allow for a longer-term follow-up to see if the intervention effects were sustainable. However, a different study design would be associated with additional ethical and organizational challenges too difficult to resolve quickly during an ongoing pandemic. Nevertheless, we believe that the findings constitute strong evidence in favour of important immediate effects of SPARK Resilience training in a challenging context.