Statistical analysis
LME, anxiety
SECONDARY
Questionnaires were scored following the provided guidelines for each questionnaire and internal consistency was assessed via Cronbach’s α coefficientThe two cohorts were analyzed both in their whole (main analysis) and separately (secondary analysis) following an intention-to-treat approach, avoiding bias related to dropouts and participants’ adherence and therefore having a conservative estimation of the treatment effect. Differences between the two groups (treated and control) and between the two cohorts at baseline characteristics, collected via the background questionnaire, were investigated using Wilcoxon test for the non-normally distributed age variable and chi-squared or fisher exact test for the categorical variables. Hedges’s effect size statistic was calculated for each variable by using the cohen.d function in the effsize R package.Linear Mixed Effect (LME) modelsIn the main analysis, all the models were adjusted for age, sex, previous meditation experience, baseline level of trait anxiety and a variable indicating the cohort to which each subject belongs to. In addition to avoid residual confounding due to covariate misbalances among the two cohorts we create a PS using the background variables resulted to be statistically significant different between the two cohorts (i.e., university, course language, academic course year, housing situation, work, sport activities, feeling stressed due to covid situation, feel competition among students) and we added the PS as covariate in the model. In the secondary analysis all the linear mixed models, as above, were adjusted for age, sex, previous meditation experience, baseline level of trait anxiety and academic course year. For the second cohort only, as follow-up data was available, an analysis fitting the same LME model as above was performed to verify if the effect of our proposed intervention remained the same, improved or worsened during the follow-up period (t2 vs t0).Normality of residuals for each model was assessed graphically through histograms and following Kim guidelinesWe also performed a multiple mediation post-hoc analysis using lavaan R packageDescriptive statistics are reported as the means ± standard deviation (SD). All analyses were performed using R 3.5.1 software