Plain English Summary
Background and study aims
In European countries, including Switzerland, as well as in many states worldwide, cannabis is the most widely used psychoactive substance (chemical known to change brain function) after alcohol and tobacco. Although approximately one in ten users develop serious problems of dependency, only a small number attend outpatient addiction counseling centers. The offer of an adherence-focused guidance enhanced web-based self-help program could potentially also reach those users who hesitate to approach such treatment centers and help them to reduce their cannabis use.
This study will test the effectiveness of an enhanced web-based self-help intervention (programme), an unenhanced web-based self-help intervention and a waiting list control in reducing cannabis use in problematic users.
Who can participate?
Adults (aged at least 18), able to read and write in German and have used cannabis at least once a week during the last 30 days
What does the study involve?
Participants are randomly allocated to one of three groups. The intervention group are given access to the adherence-focused guidance enhanced web-based self-help program (CANreduce). The active control group are given access to the unenhanced web-based self-help program. The waiting control group are placed on a waiting list; after 3 months they are given the opportunity to start the self-help program. CANreduce consists of a consumption diary, eight modules designed to help people to reduce their cannabis intake based on the principles of motivational interviewing, self-control practices, and methods of cognitive behavioural therapy. Participants can study all modules at their own pace and order. All participants are followed up 3 months after the study ends to see whether they have reduced their cannabis use.
What are the possible benefits and risks of participating?
A possible benefit to participation is taking less cannabis. Possible risks include experiencing mild cravings and depression.
Where is the study run from?
Research Institute for Public Health and Addiction (ISGF) (Switzerland)
When is the study starting and how long is it expected to run for?
July 2016 to December 2017
Who is funding the study?
Research Institute for Public Health and Addiction (ISGF) (Switzerland)
Who is the main contact?
Mr Manuel Amann
Study website
Additional identifiers
EudraCT/CTIS number
IRAS number
ClinicalTrials.gov number
Protocol/serial number
2016-00264
Study information
Scientific title
CANreduce 2.0 - the effects of an adherence-focused guidance enhanced web-based self-help program, an unenhanced web-based self-help program and a waiting list control on cannabis use in problematic cannabis users: a randomized controlled trial
Acronym
CANreduce 2.0
Study hypothesis
1. Adherence-focused guidance enhanced web-based self-help for the reduction of cannabis use (study arm 1) is more effective than the waiting list control condition (study arm 3) in reducing cannabis use
2. Unenhanced web-based self-help for the reduction of cannabis use (study arm 2) is more effective than the waiting list control condition (study arm 3) in reducing cannabis use
3. Enhanced web-based self-help (study arm 1) is more effective than unenhanced web-based self-help (study arm 2) in reducing cannabis use
Ethics approval(s)
Kantonale Ethikkommission Zürich (Ethics board of the canton Zurich), 04/07/2016, ref: BASEC-Nr. 2016-00264
Study design
Randomised controlled trial
Primary study design
Interventional
Secondary study design
Randomised controlled trial
Study setting(s)
Internet/virtual
Study type
Treatment
Patient information sheet
Not available in web format, please use contact details to request a participant information sheet.
Condition
Problematic cannabis use
Intervention
Participants are randomly allocated to one of three arms:
1. Intervention group: Adherence-focused guidance enhanced web-based self-help program
2. Active control group: Unenhanced web-based self-help program
3. Waiting control group: Waiting list
CANreduce is an automated web-based self-help tool based on classical CBT approaches for treating cannabis dependence. It will consist of a consumption diary, eight modules designed to reduce cannabis use based on the principles of motivational interviewing, self-control practices, and methods of cognitive behavioural therapy ( strategies for goal achievement, Identifying risk situations, Dealing with cannabis craving, Dealing with relapses, Working on needs, Saying “no” to foster refusal skills, Dealing with burdens, Preserving achievements). Participants can study all modules at their own pace and order, though a specific order will be advised.
The control condition is a waiting list. After 3 months their study phase is finished and they will be given the opportunity to start the self-help program. Furthermore, there will be an active control group which works with the unenhanced version of the self-help tool.
The masking technique will be single-blind, i.e. participants will not know if they work with the enhanced or unenhanced version (however, they will know if they have been assigned to the waiting list).
Once participants have completed their baseline assessment, they will be randomized by a computer program in a 1:1:1 ratio to 1 of 3 “parallel” groups, and this assignment will be automatically registered in the background database. As participants will see if they have been assigned to the waiting list, there is a risk that some might try to circumvent their assignment by registering another account in hope to end up in a different group. In case a participant surmounts the administrative hurdle, he nevertheless will be assigned to the same group for a certain amount of time, based on his IP-address.
Intervention type
Behavioural
Primary outcome measure
Quantity and the number of days per week of cannabis use. Participants enter their cannabis consumption quantity and frequency into their consumption diary every week.
Timepoints of measures will be initial assessment, after 6 weeks and at 3 months follow-up.
Secondary outcome measures
1. Severity of cannabis dependence (SDS)
2. The use of alcohol, tobacco, and other non-cannabis illicit drugs (FDA)
3. Changes in depression, anxiety and attention deficit symptoms (CES-D, GAD-7 and ASRS-V1.1)
4. Post traumatic Stress Disorder (Short Screening Scale for DSM-IV)
5. Client satisfaction (ZUF-8)
Severity of cannabis dependence and the use of alcohol, tobacco, and other non-cannabis illicit drugs will be measured at initial assessment, after 6 weeks and at 3 months follow-up.
Changes in depression, anxiety, attention deficit symptoms and the Short Screening Scale for DSM-IV Post traumatic Stress Disorder will be measured at initial assessment and at 3 months follow-up.
Client satisfaction will be measured after 6 weeks.
Overall study start date
01/07/2016
Overall study end date
01/12/2017
Reason abandoned (if study stopped)
Eligibility
Participant inclusion criteria
1. Cannabis use of at least once a week 30 days prior to study entry
2. At least 18 years old
3. At least weekly internet access and a valid email address
Participant type(s)
Mixed
Age group
Adult
Lower age limit
18 Years
Sex
Both
Target number of participants
597
Total final enrolment
775
Participant exclusion criteria
1. Current pharmacological psychiatric disease or history of psychosis, schizophrenia, bipolar type I disorder or significant current suicidal or homicidal thoughts
2. Use of other pharmacological and psycho-social treatments for cannabis use disorders
3. Inability to read or write in German
Recruitment start date
02/08/2016
Recruitment end date
31/12/2016
Locations
Countries of recruitment
Austria, Germany, Switzerland
Study participating centre
Research Institute for Public Health and Addiction (ISGF)
Konradstrasse 32
Zürich
8031
Switzerland
Sponsor information
Organisation
Research Institute for Public Health and Addiction (ISGF)
Sponsor details
Konradstrasse 32
Zurich
8031
Switzerland
+41 44 448 11 60
isgf@isgf.uzh.ch
Sponsor type
Research organisation
Website
ROR
Funders
Funder type
Government
Funder name
Research Institute for Public Health and Addiction (ISGF)
Alternative name(s)
Funding Body Type
Funding Body Subtype
Location
Results and Publications
Publication and dissemination plan
Intention to publish date
01/12/2018
Individual participant data (IPD) sharing plan
Not provided at time of registration
IPD sharing plan summary
Available on request
Study outputs
| Output type | Details | Date created | Date added | Peer reviewed? | Patient-facing? |
|---|---|---|---|---|---|
| Results article | results | 31/01/2018 | Yes | No | |
| Results article | 30/04/2021 | 05/05/2021 | Yes | No | |
| Results article | subgroup analysis | 20/04/2022 | 21/04/2022 | Yes | No |