Background
Previous studies
Aim and hypotheses
Method
Setting and recruitment procedure
Eligibility criteria
Baseline measurement
Randomization
Study arms
Intervention
Wait-list control group
Follow-up procedure
Outcome measures
Sample size
Statistical analyses
Results
Baseline characteristics of study participants
Intervention group (n = 151) | Control group (n = 152) | Test value | p-value | |
---|---|---|---|---|
Women (%) | 37.7 | 27.6 | χ2(1) = 3.524 | 0.60 |
Mean age (sd) | 27.7 (7.8) | 27.1 (6.5) | t(301) = − 0.699 | 0.485 |
Civil state | ||||
Single (%) | 58.9 | 53.9 | χ2(4) = 4.933 | 0.296 |
Partner, not married (%) | 22.5 | 28.9 | ||
Married/registered partnership (%) | 13.2 | 14.5 | ||
Divorced/separated (%) | 5.3 | 2.0 | ||
Widow/widower (%) | 0 | 0.7 | ||
Financial situation | ||||
Employment (%) | 60.3 | 63.8 | χ2(7) = 6.662 | 0.465 |
Study allowance (%) | 19.2 | 15.1 | ||
Pension (%) | 0.7 | 0.7 | ||
Sickness/activity compensation (%) | 4.6 | 9.2 | ||
Sickness benefits (%) | 3.3 | 0.7 | ||
Unemployment benefits (%) | 1.3 | 0.7 | ||
Social assistance (%) | 4.0 | 2.6 | ||
Other (%) | 6.6 | 7.2 | ||
Highest completed education | ||||
Unfinished primary school, grade school or equivalent (%) | 2.6 | 6.6 | χ2(4) = 5.437 | 0.245 |
Primary school/grade school (%) | 17.9 | 16.4 | ||
Upper secondary school, vocational school or equivalent (%) | 57.6 | 59.2 | ||
University/College (%) | 18.5 | 17.1 | ||
Other education (%) | 3.3 | 0.7 | ||
Living situation | ||||
Alone (%) | 25.8 | 27.0 | χ2(6) = 5.399 | 0.494 |
With parents (%) | 15.2 | 14.5 | ||
With husband/wife/partner/cohabitant only (%) | 12.6 | 20.4 | ||
With husband/wife/partner/cohabitant and children (%) | 9.9 | 9.9 | ||
With children only | 2.6 | 1.3 | ||
Shifting conditions (%) | 28.5 | 24.3 | ||
Other (%) | 5.3 | 2.6 | ||
Substance use and dependence | ||||
Used cannabis every week in the past 6 months (%) | 100.0 | 100.0 | ||
Cannabis use disorder according to DSM-5 (%) | 100.0 | 100.0 | ||
Used other illicit drugs (%) | 85.4 | 84.9 | χ2(1) = 0.019 | 0.891 |
Hazardous alcohol use (%) | 16.6 | 13.2 | χ2(1) = 0.692 | 0.406 |
Help-seeking | ||||
Sought professional help/treatment for cannabis use in the past 12 months (%) | 14.6 | 13.2 | χ2(1) = 0.126 | 0.722 |
Talked to relatives or friends about reducing or ending cannabis use in the past 12 months (%) | 79.5 | 78.3 | χ2(1) = 0.063 | 0.801 |
Motivation | ||||
Motivation to change cannabis use, mean score on a visual analog scale (VAS) 0–100 (sd) | 73.5 (25.5) | 74.2 (24.5) | t(301) = 0.232 | 0.816 |
VAS score: 0–25 (%) | 6.6 | 6.6 | χ2(3) = 7.667 | 0.053 |
VAS score: 26–50 (%) | 13.2 | 9.2 | ||
VAS score: 51–75 (%) | 19.9 | 33.6 | ||
VAS score: 76–100 (%) | 60.3 | 50.7 | ||
Anxiety and depression | ||||
Moderate or severe anxiety GAD-7 ≥ 10 (%) | 41.7 | 39.5 | χ2(1) = 0.159 | 0.690 |
Moderate or depression MADRS ≥ 20 (%) | 62.3 | 58.6 | χ2(1) = 0.433 | 0.510 |
Follow-up completers
Reasons for using internet intervention and utilization of the intervention
N | Meana | SD | |
---|---|---|---|
Can remain anonymous | 256 | 8.1 | 2.9 |
Can decide my own goal within the treatment | 255 | 7.8 | 2.7 |
Do not have to tell other people that you are seeking treatment | 256 | 7.3 | 3.2 |
Do not have to travel to participate in treatment | 253 | 7.1 | 3.2 |
Can have access to treatment at any time | 254 | 7.0 | 2.9 |
Cannabis use is not documented in a medical record | 256 | 6.6 | 3.8 |
Do not have to go to a clinic | 254 | 6.0 | 3.8 |
Step (days since last use) | Visited step pagea | Moduleb | Visited module page | Completed module |
---|---|---|---|---|
Step 0 (0–1 day) | 82 (53.9%) | Finding motivation to change cannabis use | 102 (67.5%) | 90 (59.6%) |
Setting a goal of a time period when not to use cannabis | 85 (56.3%) | 78 (51.7%) | ||
Mean (SD) goal in number of cannabis abstinent daysc | 62.6 (68.1) | |||
Step 1 (2–8 days) | 50 (32.9%) | Learning practical tips on changing cannabis use through self-control | 68 (45.0%) | 57 (37.7%) |
Picturing yourself free from cannabis | 49 (32.5%) | 28 (18.5%) | ||
How cannabis affects your thinking | 26 (17.2%) | 20 (13.2%) | ||
Step 2 (9–21 days) | 31 (20.4%) | Alternative ways to manage cravings | 33 (21.9%) | 22 (14.6%) |
Finding ways to sleep better | 32 (21.2%) | 22 (14.6%) | ||
Learning to deal with difficult emotions | 25 (16.6%) | 17 (11.3%) | ||
Practicing the handling of social pressure | 18 (11.9%) | 15 (9.9%) | ||
Step 3 (22–42 days) | 23 (15.1%) | Learning to get help from others | 11 (7.3%) | 9 (6.0%) |
Identifying risk situations that trigger the urge to use cannabis | 15 (9.9%) | 1 (0.7%) | ||
Alternative plans for handling problems | 15 (9.9%) | 12 (7.9%) | ||
Relapse prevention (including tips on maintaining motivation to sustain abstinence from cannabis use over the long term) | 9 (6.0%) | 6 (4.0%) | ||
Introduction (all) | 137 (90.7%) | Used the cannabis calendar | 96 (63.6%) | |
Sent a message to therapist | 76 (50.3%) | |||
Mean (SD number of visits to the program | 62.4 (110.6) | |||
Mean (SD) days between first and last visit | 25.0 (33.6) |
Time by group effects
Intention-to-treat analyses (n = 303) | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Outcome | Pre M (SD) or n (%) | Post M (SD) or n (%) | Outcome modelling | ||||||||||
Intervention | Control | Intervention | Control | Type | Intercept | Time | Group | Time × group | |||||
Number of days without cannabis use (past week) | 1.60 | (2.03) | 1.38 | (1.94) | 4.16 | (2.74) | 3.27 | (2.70) | Poisson | B = 0.32 (SE = 0.11, p < .001) | B = 0.85 (SE = 0.14, p < .001) | B = 0.14 (SE = 0.15, p = .35) | B = 0.09 (SE = 0.19, p = .63) |
Gram cannabis (past week) | 5.98 | (5.64) | 6.87 | (7.99) | 2.30 | (2.92) | 4.06 | (6.69) | Poisson | B = 1.93 (SE = 0.09, p < .001) | B = − 0.45 (SE = 0.11, p < .001) | B = − 0.14 (SE = 0.12, p = .25) | B = − 0.27 (SE = 0.18, p = .12) |
Number of DSM-5 cannabis use disorder criteria | 7.93 | (2.22) | 8.18 | (2.05) | 5.02 | (2.61) | 5.74 | (2.69) | Gaussian | B = 8.18 (SE = 0.17, p < .001) | B = − 2.17 (SE = 0.28, p < .001) | B = − 0.25 (SE = 0.25, p = .31) | B = − 0.61 (SE = 0.48, p = .2) |
CAST score | 14.05 | (4.33) | 14.07 | (4.31) | 8.26 | (5.10) | 9.73 | (5.37) | Gaussian | B = 14.07 (SE = 0.35, p < .001) | B = − 3.8 (SE = 0.53, p < .001) | B = − 0.02 (SE = 0.49, p = .97) | B = − 1.63 (SE = 0.9, p = .07) |
Help-seeking (n, %) | 17 | (11.26) | 19 | (12.5) | 12 | (24) | 17 | (21.79) | Binomial | B = − 1.95 (SE = 0.25, p < .001) | B = 0.56 (SE = 0.28, p = .05) | B = − 0.12 (SE = 0.36, p = .74) | B = 0.25 (SE = 0.49, p = .61) |
Number of standard glasses of alcohol (past week) | 6.29 | (8.03) | 5.62 | (8.11) | 4.28 | (5.11) | 5.44 | (9.45) | Poisson | B = 1.73 (SE = 0.12, p < .001) | B = − 0.09 (SE = 0.2, p = .65) | B = 0.11 (SE = 0.16, p = .47) | B = − 0.26 (SE = 0.25, p = .3) |
SCS score | 48.87 | (13.26) | 49.05 | (14.52) | 54.10 | (14.70) | 54.77 | (15.84) | Gaussian | B = 49.05 (SE = 1.17, p < .001) | B = 4.83 (SE = 1.34, p < .001) | B = − 0.17 (SE = 1.59, p = .91) | B = 0.17 (SE = 2.22, p = .94) |
MADRS score | 21.62 | (8.91) | 20.92 | (9.79) | 16.78 | (10.99) | 16.22 | (11.27) | Gaussian | B = 20.92 (SE = 0.79, p < .001) | B = − 4.11 (SE = 0.94, p < .001) | B = 0.69 (SE = 1.07, p = .52) | B = − 0.67 (SE = 1.68, p = .69) |
GAD-7 score | 9.28 | (5.50) | 8.67 | (5.34) | 6.60 | (5.57) | 6.36 | (5.52) | Gaussian | B = 8.67 (SE = 0.43, p < .001) | B = − 1.97 (SE = 0.52, p < .001) | B = 0.61 (SE = 0.62, p = .33) | B = − 0.19 (SE = 0.85, p = .82) |
Excluding participants who sought other treatment (n = 267) | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Pre M (SD) or n (%) | Post M (SD) or n (%) | Outcome modelling | |||||||||||
Intervention | Control | Intervention | Control | Type | Intercept | Time | Group | Time × group | |||||
Number of days without cannabis use (past week) | 1.52 | (1.99) | 1.29 | (1.83) | 4.26 | (2.68) | 3.16 | (2.48) | Poisson | B = 0.32 (SE = 0.12, p = .01) | B = 0.83 (SE = 0.15, p < .001) | B = 0.05 (SE = 0.17, p = .76) | B = 0.27 (SE = 0.21, p = .2) |
Gram cannabis (past week) | 5.82 | (5.53) | 6.99 | (8.18) | 2.03 | (2.60) | 4.05 | (6.96) | Poisson | B = 1.95 (SE = 0.1, p < .001) | B = − 0.42 (SE = 0.13, p < .001) | B = − 0.12 (SE = 0.13, p = .36) | B = − 0.42 (SE = 0.19, p = .02) |
Number of DSM-5 cannabis use disorder criteria | 7.79 | (2.26) | 8.04 | (2.03) | 4.42 | (2.46) | 5.87 | (2.50) | Gaussian | B = 8.11 (SE = 0.18, p < .001) | B = − 2.06 (SE = 0.3, p < .001) | B = − 0.26 (SE = 0.26, p = .32) | B = − 1.36 (SE = 0.52, p = .01) |
CAST score | 13.62 | (4.26) | 13.90 | (4.24) | 7.79 | (5.07) | 9.80 | (5.10) | Gaussian | B = 14.05 (SE = 0.38, p < .001) | B = − 3.45 (SE = 0.56, p < .001) | B = − 0.15 (SE = 0.53, p = .78) | B = − 1.9 (SE = 0.99, p = .06) |
Number of standard glasses of alcohol (past week) | 6.48 | (7.97) | 5.62 | (8.08) | 4.92 | (5.42) | 4.38 | (5.48) | Poisson | B = 1.65 (SE = 0.13, p < .001) | B = − 0.22 (SE = 0.16, p = .17) | B = 0.18 (SE = 0.17, p = .27) | B = 0.09 (SE = 0.22, p = .69) |
SCS score | 49.18 | (13.67) | 49.74 | (14.57) | 56.97 | (13.14) | 55.93 | (15.97) | Gaussian | B = 49.78 (SE = 1.27, p < .001) | B = 5.19 (SE = 1.64, p < .001) | B = − 0.54 (SE = 1.71, p = .75) | B = 2.45 (SE = 2.67, p = .36) |
MADRS score | 21.17 | (9.03) | 20.48 | (9.58) | 14.29 | (9.98) | 16.20 | (11.91) | Gaussian | B = 20.36 (SE = 0.86, p < .001) | B = − 3.22 (SE = 1.1, p < .001) | B = 0.93 (SE = 1.14, p = .41) | B = − 3.3 (SE = 1.93, p = .09) |
GAD-7 score | 8.84 | (5.43) | 8.17 | (5.08) | 5.61 | (5.18) | 5.80 | (5.12) | Gaussian | B = 8.09 (SE = 0.44, p < .001) | B = − 2.11 (SE = 0.62, p < .001) | B = 0.89 (SE = 0.63, p = .16) | B = − 0.76 (SE = 0.96, p = .43) |