Table 3

Results of the ANCOVAs and Cohen’s d for the primary and secondary outcome measures (ITT sample) at post-treatment and 6 months follow-up

OutcomeT2† between-groups effectT3† between-groups effect
Cohen’s d (95% CI)ANCOVA‡ F(1,114)Cohen’s d (95% CI)ANCOVA‡ F(1,114)
Primary outcome
 PSS-14 (0–56)0.74 (0.30 to 1.19)12.70***0.59 (0.14 to 1.04)2.17**
Mental health
 SMBQ (1–7)0.95 (0.53 to 1.37)23.71***0.39 (0.21 to 0.99)1.44
  Physical fatigue0.59 (0.17 to 1.01)8.36**0.30 (0.14 to 0.75)2.47
  Cognitive weariness0.57 (0.15 to 0.99)7.04**0.50 (0.05 to 0.94)4.71*
  Tension0.36 (0.05 to 0.78)5.02*0.31 (0.13 to 0.76)3.88
  Listlessness0.33 (0.08 to 0.74)2.960.08 (0.36 to 0.52)0.98
  MADRS-S (0–54)0.86 (0.25 to 1.46)9.70*0.29 (0.16 to 0.74)1.74
 ISI (0–28)0.34 (0.07 to 0.76)4.85*0.39 (0.01 to 0.78)6.17*
Work related
 WEMS (32–192)§0.59 (1.01 to 0.17)11.37***0.11 (0.56 to 0.34)0.31
  Supportive work conditions (1–6)§0.30 (0.72 to 0.13)4.45*0.05 (0.44 to 0.53)0.04
  Internal work experience (1–6)§0.36 (0.78 to 0.07)5.77*0.04 (0.52 to 0.44)0.15
  Autonomy (1–6)§0.12 (0.31 to 0.54)0.230.10 (0.38 to 0.58)0.60
  Time experience (1–6)§0.16 (0.58 to 0.27)0.860.00 (0.48 to 0.48)2.58
  Management (1–6)§0.40 (0.83 to 0.02)10.51**0.05 (0.54 to 0.43)0.66
  Process of change (1–6)§0.46 (0.89 to 0.03)9.54**0.12 (0.60 to 0.36)0.30
 Absenteeism (TiC-P)¶0.62 (0.45 to 1.70)1.590.37 (1.70 to 0.96)0.37
 Presenteeism (TiC-P)¶0.29 (0.83 to 0.24)1.210.28 (0.91 to 0.36)0.78
AUDIT (0–40)
  • Significance levels used: *p<0.05, **p<0.01; ***p<0.001.

  • †Missing data imputed by multiple imputation.

  • ‡Controlling for pretreatment scores (T1).

  • §Higher scores indicate better outcomes.

  • ¶In relation to the previous month.

  • ANCOVA, analysis of covariance; PSS-14, Perceived Stress Scale; SMBQ, Shirom-Melamed Burnout Questionnaire; MADRS-S, Montgomery Åsberg Depression Rating Scale-self-assessment; ISI, Insomnia Severity Index; ITT, intention to treat; WEMS, Work Experience Measurement Scale; AUDIT, Alcohol Use Disorders Identification Test; TiC-P, Trimbos and Institute of Medical Technology Assessment Cost Questionnaire for Psychiatry.