Table 2.
Means, standard deviations, and effect sizes (Cohen's d) for primary and secondary outcomes by group.
| Estimated marginal means |
Percentage changes from pre-treatment |
Within-group effect sizes from pre-treatment |
Between-group effect size |
|||||
|---|---|---|---|---|---|---|---|---|
| Pre-treatment | Post-treatment | 4-Week follow-up | To post-treatment | To 4-week follow-up | To post-treatment | To 4-week follow-up | At post-treatment | |
| Primary outcomes | ||||||||
| GAD-7 | ||||||||
| ICBT | 9.76 (4.48) | 3.23 (2.77) | 2.87 (1.99) | 67 [52,77] | 71 [60,78] | 1.75 [1.10,2.41] | 1.98 [1.31,2.66] | 1.62 [1.00,2.24] |
| WLC | 8.75 (4.09) | 9.02 (4.15) | – | -3 [−24,15] | – | −0.06 [−0.59,0.46] | – | |
| GLTEQ | ||||||||
| ICBT | 20.08 (17.98) | 34.13 (20.48) | 49.59 (26.06) | 70 [25,115] | 147 [90,204] | 0.73 [0.16,1.30] | 1.32 [0.71,1.93] | 0.27 [−0.27,0.81] |
| WLC | 30.11 (16.70) | 29.58 (13.24) | – | −2 [−20,16] | – | −0.04 [−0.56,0.49] | – | |
| PHQ-9 | ||||||||
| ICBT | 11.00 (4.11) | 4.32 (2.45) | 4.00 (2.29) | 61 [50,69] | 64 [53,72] | 1.97 [1.30,2.65] | 2.10 [1.41,2.79] | 1.09 [0.51,1.66] |
| WLC | 9.18 (4.99) | 8.72 (5.07) | – | 5 [−21,25] | – | 0.09 [−0.43,0.61] | – | |
| Secondary outcomes | ||||||||
| CAQ-Total | ||||||||
| ICBT | 1.73 (0.51) | 1.14 (0.44) | 0.80 (0.45) | 34 [22,44] | 54 [41,64] | 1.24 [0.63,1.84] | 1.94 [1.26,2.61] | 0.92 [0.36,1.49] |
| WLC | 1.79 (0.51) | 1.64 (0.61) | – | 9 [−6,22] | – | 0.29 [−0.24,0.81] | – | |
| CAQ-Attention | ||||||||
| ICBT | 1.34 (0.67) | 0.91 (0.62) | 0.55 (0.57) | 32 [8,50] | 59 [35,74] | 0.66 [0.10,1.23] | 1.26 [0.65,1.87] | 0.95 [0.38,1.51] |
| WLC | 1.73 (0.66) | 1.51 (0.65) | – | 13 [−4,27] | – | 0.33 [−0.19,0.86] | – | |
| CAQ-Avoidance | ||||||||
| ICBT | 2.10 (0.83) | 1.42 (0.68) | 1.12 (0.84) | 33 [17,45] | 47 [26,62] | 0.90 [0.32,1.48] | 1.18 [0.57,1.78] | 0.28 [−0.27,0.82] |
| WLC | 1.56 (0.75) | 1.60 (0.63) | – | −2 [−20,13] | – | −0.05 [−0.58,0.47] | – | |
| CAQ-Fear | ||||||||
| ICBT | 1.76 (0.57) | 1.12 (0.56) | 0.75 (0.47) | 36 [21,49] | 58 [44,68] | 1.12 [0.53,1.72] | 1.93 [1.26,2.60] | 0.94 [0.37,1.51] |
| WLC | 1.98 (0.55) | 1.74 (0.73) | – | 12 [−4,26] | – | 0.38 [−0.15,0.90] | – | |
| DASS-21-Total | ||||||||
| ICBT | 22.60 (8.10) | 11.03 (5.22) | 9.40 (5.32) | 51 [41,61] | 58 [48,69] | 1.70 [1.05,2.35] | 1.93 [1.26,2.60] | 0.98 [0.41,1.55] |
| WLC | 20.22 (9.43) | 18.03 (8.53) | – | 11 [−6,28] | – | 0.24 [−0.28,0.77] | – | |
| DASS-21-Depression | ||||||||
| ICBT | 7.36 (3.67) | 3.45 (2.47) | 2.77 (2.46) | 53 [36,66] | 62 [44,74] | 1.25 [0.64,1.86] | 1.47 [0.84,2.09] | 0.55 [0.00,1.10] |
| WLC | 5.97 (4.11) | 5.39 (4.22) | – | 10[−24,34] | – | 0.14 [−0.39,0.66] | – | |
| DASS-21-Anxiety | ||||||||
| ICBT | 7.00 (3.76) | 3.36 (2.14) | 2.72 (2.22) | 52 [37,64] | 61 [45,73] | 1.19 [0.59,1.79] | 1.39 [0.77,2.01] | 0.67 [0.12,1.23] |
| WLC | 6.43 (3.43) | 5.10 (2.91) | – | 21 [0,37] | – | 0.42 [−0.11,0.95] | – | |
| DASS-21-Stress | ||||||||
| ICBT | 8.24 (3.36) | 4.20 (2.37) | 4.01 (2.42) | 49 [36,62] | 51 [38,64] | 1.39 [0.77,2.01] | 1.44 [0.82,2.07] | 1.26 [0.67,1.85] |
| WLC | 7.82 (3.30) | 7.53 (2.87) | – | 4 [−11,19] | – | 0.09 [−0.43,0.62] | – | |
| SF-12-Mental | ||||||||
| ICBT | 38.06 (6.19) | 47.34 (8.27) | – | 24 [15,34] | – | 1.27 [0.66,1.88] | – | 0.23 [−0.33,0.79] |
| WLC | 42.24 (8.98) | 45.41 (8.46) | – | 8 [−1,16] | – | 0.36 [−0.18,0.91] | – | |
| SF-12-Physical | ||||||||
| ICBT | 39.44 (8.62) | 44.95 (7.98) | – | 14 [5,23] | – | 0.66 [0.09,1.23] | – | −0.17 [−0.73,0.39] |
| WLC | 43.66 (8.34) | 46.20 (6.66) | – | 6 [−1,13] | – | 0.33 [−0.21,0.88] | – | |
Note. CAQ = Cardiac Anxiety Questionnaire; DASS-21 = Depression, Anxiety, and Stress 21-item Scale; GAD-7 = Generalized Anxiety Disorder 7-item scale; GLTEQ = Godin Leisure-Time Exercise Questionnaire; PHQ-9 = Patient Health Questionnaire 9-item scale; SF-12 = Short Form 12-item Health Survey; ICBT = Internet-delivered cognitive behavioural therapy; WLC = waiting-list control. Standard deviations are shown in rounded parentheses for the estimated means; 95% confidence intervals are shown in square parentheses for the percentage changes and effect sizes.