Table 2

Instrumental variable analysis of primary outcomes at 1-year follow-up, with allocated group as an instrument for the implementation variables

Outcome/implementation variablesN (K)Coefficient95% CIP value
Risk of depression
 Dose5508 (65)0.08−0.01 to 0.170.065
 Fidelity5667 (66)0.01−0.004 to 0.020.219
 Reach5673 (65)0.02−0.01 to 0.040.284
 Quality6139 (73)0.12−0.07 to 0.310.199
 Practice (postintervention)5960 (73)0.40−0.24 to 1.030.226
 Practice (1 year follow-up)6196 (73)0.56−0.33 to 1.440.218
Social–emotional–behavioural function
 Dose5423 (65)0.05−0.001 to 0.090.056
 Fidelity5577 (66)0.01−0.001 to 0.010.109
 Reach5580 (65)0.01−0.01 to 0.020.185
 Quality6046 (73)0.07−0.03 to 0.580.150
 Practice (postintervention)5874 (73)0.18−0.14 to 0.490.274
 Practice (1-year follow-up)6106 (73)0.26−0.18 to 0.710.243
 Dose5484 (65)−0.03−0.11 to 0.040.363
 Fidelity5643 (66)−0.001−0.01 to 0.010.781
 Reach5649 (65)−0.004−0.03 to 0.020.742
 Quality6116 (73)−0.02−0.18 to 0.150.849
 Practice (postintervention)5936 (73)−0.003−0.55 to 0.540.992
 Practice (1-year follow-up)6168 (73)−0.02−0.76 to 0.730.967
  • Coefficient: unstandardised regression coefficient (slope) of the instrumental variable analysis (representing the increase in the outcome per 1 unit increase in the predictor) with cluster-robust maximum likelihood estimation, including schools (clusters) as random effects, and adjusted for the baseline levels of student mental health (ie, risk of depression, social–emotional–behavioural functioning, well-being), cohort, school size, school sex, and country. Dose is the number of SBMT sessions that students received. Quality is the teacher competency delivering the SBMT independently evaluated by using the Mindfulness-based Interventions Teaching Assessment Criteria. Fidelity is the independently rated percentage of the total original SBMT content delivered by the teacher. Reach is the percentage of school study students receiving ≥67% of SBMT sessions. Practice is the amount of home-based student mindfulness practice during/after the intervention.

  • K, number of clusters (schools) in analysis; n, number of students in analysis; p, p value for the slope; SBMT, school-based mindfulness training.