Table 5.
Results for the between-study arma comparisons from the linear (and logistic) regression models and calculated effect sizes based on the imputed dataset (50 imputations).
| Characteristics | beta | SE | t | P | Cohen's d (95% CI) | |
| Frequency of cannabis use b |
|
|
|
|
|
|
|
|
(Intercept) | -3.95 | 0.58 | -6.76 | <.001 |
|
|
|
Arm 1 vs arm 3 | 0.70 | 0.32 | 2.16 | .03 c | 0.20 (-0.07 to 0.47) |
|
|
Arm 2 vs arm 3 | -0.05 | 0.33 | -0.16 | .87 | -0.14 (-0.43 to 0.14) |
|
|
(Intercept) | -3.25 | 0.56 | -5.79 | <.001 |
|
|
|
Arm 2 vs arm 1 | -0.75 | 0.32 | -2.39 | .02 | 0.34 (0.07 to 0.61) |
| Quantity of cannabis use d |
|
|
|
|
|
|
|
|
(Intercept) | -14.50 | 2.24 | -6.46 | <.001 |
|
|
|
Arm 1 vs arm 3 | 4.73 | 2.50 | 1.89 | .06 | 0.09 (-0.19 to 0.36) |
|
|
Arm 2 vs arm 3 | 3.77 | 2.42 | 1.56 | .12 | 0.06 (-0.22 to 0.35) |
|
|
(Intercept) | -9.78 | 1.92 | -5.09 | <.001 |
|
|
|
Arm 2 vs arm 1 | -0.96 | 2.43 | -0.39 | .69 | 0.01 (-0.26 to 0.28) |
| CUDIT e |
|
|
|
|
|
|
|
|
(Intercept) | -10.39 | 1.61 | -6.46 | <.001 |
|
|
|
Arm 1 vs arm 3 | 0.24 | 1.29 | 0.19 | .85 | 0.09 (-0.18 to 0.37) |
|
|
Arm 2 vs arm 3 | 1.19 | 1.20 | 0.99 | .32 | 0.21 (-0.07 to 0.49) |
|
|
(Intercept) | -10.14 | 1.68 | -6.05 | <.001 |
|
|
|
Arm 2 vs arm 1 | 0.95 | 1.16 | 0.82 | .41 | -0.12 (-0.39 to 0.14) |
| SDS f |
|
|
|
|
|
|
|
|
(Intercept) | -4.68 | 0.64 | -7.34 | <.001 |
|
|
|
Arm 1 vs arm 3 | 0.03 | 0.58 | 0.05 | .96 | 0.08 (-0.19 to 0.36) |
|
|
Arm 2 vs arm 3 | 0.10 | 0.56 | 0.17 | .86 | 0.07 (-0.21 to 0.35) |
|
|
(Intercept) | -4.65 | 0.65 | -7.19 | <.001 |
|
|
|
Arm 2 vs arm 1 | 0.07 | 0.55 | 0.13 | .90 | 0.02 (-0.25 to 0.28) |
| MHI-5 g |
|
|
|
|
|
|
|
|
(Intercept) | -43.91 | 4.33 | -10.15 | <.001 |
|
|
|
Arm 1 vs arm 3 | 0.96 | 3.44 | 0.28 | .78 | 0.01 (-0.27 to 0.28) |
|
|
Arm 2 vs arm 3 | -1.38 | 3.42 | -0.40 | .69 | -0.09 (-0.38 to 0.19) |
|
|
(Intercept) | -42.95 | 4.14 | -10.37 | <.001 |
|
|
|
Arm 2 vs arm 1 | -2.34 | 3.28 | -0.71 | .48 | 0.11 (-0.16 to 0.38) |
| Alcohol use in the last 30 days (risky) |
|
|
|
|
|
|
|
|
(Intercept) | -2.84 | 0.56 | -5.09 | <.001 |
|
|
|
Arm 1 vs arm 3 | 0.32 | 0.63 | 0.52 | .61 | -0.10 (-0.38 to 0.17) |
|
|
Arm 2 vs arm 3 | 0.83 | 0.73 | 1.14 | .25 | -0.16 (-0.44 to 0.12) |
|
|
(Intercept) | -2.52 | 0.46 | -5.46 | <.001 |
|
|
|
Arm 2 vs arm 1 | 0.51 | 0.61 | 0.84 | .40 | 0.06 (-0.20 to 0.33) |
aStudy arm 1: self-help with chat; study arm 2: self-help without chat; study arm 3: waiting list.
bBased on the weekly number of cannabis use days according to the consumption diary.
cSignificant and borderline significant differences and effect sizes are in italics.
dBased on the weekly number of standard cannabis joints according to the consumption diary.
eCannabis Use Disorders Identification Test (CUDIT) scores range from 0 to 40 with a cutoff of >8 for a cannabis use disorder.
fSeverity of Dependence Scale (SDS) scores range from 0 to 15 with a cutoff of ≥4 for cannabis dependence.
gMental Health Inventory (MHI-5): higher values represent improved symptoms. MHI-5 scores range from 0 to 100 with a cutoff of <70 for clinically relevant symptoms.