S T U D Y P R O T O C O L Open Access
Efficacy of a mobile phone-based life-skills
training program for substance use
prevention among adolescents: study
protocol of a cluster-randomised controlled
, Raquel Paz Castro, Andreas Wenger and Michael P. Schaub
Background: Life-skills trainings conducted within the school curriculum are effective in preventing the onset and
escalation of substance use among adolescents. However, their dissemination is impeded due to their large
resource requirements. Life-skills training provided via mobile phones might represent a more economic and
scalable approach. The main objective of the planned study is to test the efficacy of a mobile phone-based life-skills
training to prevent substance use among adolescents within a controlled trial.
Methods/design: The efficacy of a mobile phone-based life-skills training to prevent substance use among
adolescents will be tested in comparison to an assessment only control group, within a cluster-randomised controlled
trial with two follow-up assessments after 6 and 18 months. The fully automated program is based on social cognitive
theory and addresses self-management skills, social skills, and substance use resistance skills. Participants of the
intervention group will receive up to 4 weekly text messages over 6 months in order to stimulate (1) positive outcome
expectations, e.g., on using self-management skills to cope with stress, (2) self-efficacy, e.g., to resist social pressure, (3)
observational learning, e.g. of interpersonal competences, (4) facilitation, e.g., of strategies to cope with negative
emotions, and (5) self-regulation, e.g., by self-monitoring of stress and emotions. Active program engagement will be
stimulated by interactive features such as quiz questions, message- and picture-contests, and integration of a friendly
competition with prizes in which program users collect credits with each interaction. Study participants will be 1312
students between the ages of 14 and 16 years from approximately 100 secondary school classes. Primary outcome
criteria will be problem drinking according to the short form of the Alcohol Use Disorders Identification Test and
cigarette smoking within the last 30 days preceding the follow-up assessment at month 18.
Discussion: This is the first study testing the efficacy of a mobile phone-based life-skills training for substance use
prevention among adolescents within a controlled trial. Given that this intervention approach proves to be effective, it
could be easily implemented in various settings and would reach large numbers of young people in a cost-effective
Trial registration: ISRCTN41347061 (registration date: 21/07/2018).
Keywords: Life-skills, Substance use, Prevention, Adolescents, Mobile phone
* Correspondence: firstname.lastname@example.org
Swiss Research Institute for Public Health and Addiction, Zurich University,
Konradstrasse 32, 8005 Zurich, Switzerland
© The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Haug et al. BMC Public Health (2018) 18:1102
Several biological, psychological, and social transitions
that occur during adolescence are essential for a young
person’s later-life trajectory [1,2]. These transitions offer
opportunities for them to gain skills to achieve greater au-
tonomy from adults, build social connections with peers,
develop a positive body image, and form a sense of iden-
tity. However, these transitions also facilitate exploration
and risk taking at a stage when cognitive functions of the
brain are not yet fully developed . Shifts of emotional
regulations and increased risky behaviours result in vul-
nerabilities for mental and substance use disorders, which
constitute the biggest contributors to the health burden of
10- to 24-year-old individuals . Substance use and the
development of substance use disorders often first emerge
during adolescence and co-occur with mental disorders
. The Swiss data of the Health Behaviour in
School-aged Children (HBSC) study  showed noticeably
increases in the lifetime prevalence of alcohol, tobacco
and cannabis consumption over the age groups of
11-to-15-year-olds. The prevalence of regular cigarette
smoking (weekly or daily) increased from 2% among
13-year old boys to 12% among 15-year-old boys and from
2% in 13-year old girls to 9% in 15-year old girls. The
prevalence of binge drinking increased from 19% in
14-year old boys to 27% in 15-year old boys and from 14%
in 14-year old girls to 23% in 15-year old girls.
A systematic review of studies assessing the effectiveness
of prevention, early intervention, and harm reduction in
young people for tobacco, alcohol, and illicit drugs demon-
strated the effectiveness of taxation, public consumption
bans, advertising restrictions, and minimum legal age, as
well as the potential effectiveness of preventative interven-
tions that deliver life-skills training in educational settings
. Schools are particularly suitable settings to reach ado-
lescents with preventative interventions because of the ease
of delivery and access to young people within compulsory
secondary education. A Cochrane Review on school-based
programs for the prevention of tobacco smoking con-
cluded that combined social competence and social influ-
ence interventions had a significant effect at 1 year and at
longest follow-up (OR 0.49, 95% CI 0.28 to 0.87), whereas a
social influences program on its own, multimodal
community-wide initiatives, and information-only interven-
tions were found to be ineffective. Another Cochrane re-
view on school-based prevention programs for alcohol
misuse in young people  concluded that certain generic
psychosocial and developmental prevention programs can
be effective. However, the methodological quality of the tri-
als included in the analysis was poor, and this did not allow
for any quantitative pooling of data.
The majority of the generic programmes addressing
social competences and social influences which were in-
cluded in the above-cited reviews can be described as
life-skills trainings and primarily rely on Bandura’s social
learning theory  which hypothesizes that children and
adolescents learn substance use by modelling, imitation,
and reinforcement, influenced by individual cognitions,
attitudes. Furthermore, based on the social influences
approach,  substance use susceptibility is increased
by poor personal and social skills and young people initi-
ate drug use as a result of pressure from peers, family
and the media.
Generic life skills programs to prevent substance use,
like the IPSY program, developed in Germany orthe
ALERT  or Life Skills Training  programs devel-
oped in the US, typically combine training in
self-management skills (e.g., coping with stress, emotional
self-regulation, goal setting), social skills (e.g., assertiveness,
communication skills) and substance use resistance skills
(e.g. resisting peer pressure to drink alcohol, recognizing
and resisting media influences promoting cigarette smok-
ing, normative expectations about substance use).
Although these life-skills training programs were effective
at preventing the onset of specific substances [7,11,14]o
at decreasing problematic substance use , their imple-
challenges . First, teachers and other professionals need
the time, motivation, knowledge and skills to deliver the
program. Second, extensive resources, in terms of
personnel, money, and time allocated to deliver substance
use prevention, are required to prepare and administer such
Electronically-delivered interventions (e.g. via com-
puter, Internet or mobile phone) have the potential to
overcome the above-mentioned obstacles that hinder
successful program implementation and larger-scale dis-
semination of life-skills training in schools.
Electronically-delivered interventions have a wide reach
at a low cost, and offer the opportunity to automatically
deliver individually-tailored contents that can be
accessed at any time and in any place . Furthermore,
electronically-delivered interventions might be more ap-
pealing for adolescents, because they can better ensure
privacy and tailor contents to their needs.
A recent systematic review of alcohol and other drug
prevention programs facilitated by computers or the
Internet  identified nine trials of online prevention
programs, of which six demonstrated significant, but
modest effects for alcohol and/or other drug use out-
comes. The programs were delivered in the US,
Australia and the Netherlands and provided between 1
and 12 online curriculum-based standard lessons or tai-
lored feedback. All programs were universal, i.e., deliv-
ered interventions to all students regardless of their level
of risk, and were primarily based on principles of the so-
cial learning theory , the social influences approach
 and the social cognitive theory [18,19].
Haug et al. BMC Public Health (2018) 18:1102 Page 2 of 9
Beyond traditional personal computers, a promising
means of delivering prevention programs is to do so re-
motely through the use of mobile technologies. In
Switzerland, as in most other developed countries, almost
all (98%) adolescents between the ages of 12 and 19 own a
mobile phone, and 97% of these phones are smartphones
. Most adolescents are familiar with how to use mobile
phones and typically use them on a daily basis for texting,
taking pictures, playing games etc. Mobile phone-based
interventions can provide almost constant support to
users, in comparison to interventions that can only be
accessed at specific times or locations and they provide a
discrete and confidential means of intervention delivery
. Particularly mobile phone text messaging is a suitable
means of delivering individually tailored messages via mo-
bile phone. This interactive service allows cost-effective,
instantaneous, direct delivery of messages to individuals.
Several recent reviews underline the potential and efficacy
of text messaging-based interventions in various health
domains (e.g., diabetes self-management, weight loss,
physical activity, smoking cessation, and medication ad-
herence) and for different target groups, including adoles-
cents and young adults [22–25].
Within a pre-post study in Switzerland, the acceptance
and potential effectiveness of a mobile phone-based
life-skills training program for substance use prevention
among non-smoking vocational school students was
tested . This program was based on social cognitive
theory and addressed self-management skills, social
skills, and substance use resistance skills. Program par-
ticipants received up to 3 weekly text messages over
6 months. Active program engagement was stimulated
by interactive features such as quiz questions, message
and picture-contests, and integration of a friendly com-
petition with prizes in which program users collected
credits with each interaction. A total of 1067 vocational
students who owned a mobile phone and were not regu-
lar cigarette smokers were invited to participate in the
program. Of these, 877 (82.2%) participated in the pro-
gram and the associated study. Pre-post comparisons re-
vealed decreased perceived stress and increases in
several life skills addressed between baseline and the
follow-up assessment. The proportion of adolescents
with at-risk alcohol use significantly declined from
20.2% at baseline to 15.5% at follow-up.
Based on these results, showing high-level acceptance
and promising effectiveness of a mobile phone-delivered
life-skills training program among vocational school stu-
dents, a reasonable next step is to test the efficacy of this
interventional approach within a controlled trial. How-
ever, as the age of onset of substance use is strongly in-
creasing between the ages of 14 and 16 , it might be
even more appropriate to test this universal prevention
approach among secondary school students.
Within this study protocol, we describe a cluster rando-
mised controlled trial testing the efficacy of a similar mo-
bile phone-based life-skills training program to prevent
substance use among secondary school students.
Design and hypotheses
A two-arm cluster-randomised controlled trial will be
conducted to test the efficacy of the SmartCoach, a mo-
bile phone-based life-skills training program to prevent
substance use among secondary school students. The ef-
ficacy of the intervention will be tested in comparison to
an assessment only control group. The study partici-
pants will be assessed at baseline and at 6- and
18-months follow-up (Fig. 1). Our main hypothesis is
that the individually tailored intervention program with
a duration of 6 months will be more effective than as-
sessment only, to prevent the onset and escalation of
problematic alcohol and tobacco use at 18-months
Participants, setting and procedure
We will test the intervention in secondary school stu-
dents aged between 14 and 16 (grades 8 and 9). In this
age group the prevalence of experimental and regular
use of alcohol, tobacco and cannabis is increasing no-
ticeably . However, only a minority has established
problematic or disordered substance use [5,27]. Further-
more, nearly all adolescents at this age are familiar with
how to use mobile phones and typically use them on a
daily basis. According to the latest representative survey
on media use in adolescents in Switzerland, 98% of the
adolescents aged 14 and 15 years own a mobile phone
and 98% use a mobile phone daily or several times per
week . Secondary schools in the German speaking
part of Switzerland will be invited to participate in the
study by cooperating regional centres for addiction
Employees of the above-mentioned centres for addic-
tion prevention will arrange information sessions with a
duration of 60 min in participating secondary school
classes during regular school lessons reserved for health
education. These information sessions will be led by jun-
ior scientist from the Swiss Research Institute for Public
Health and Addiction, who are experienced in the work
with young people, the provision of preventive interven-
tions and trained on the study and on the program to be
The parents of the secondary school students in par-
ticipating classes will be informed at least 1 week in ad-
vance of this session. They will receive a letter including
information about the study and the intervention pro-
gram and the parents are asked to give written informed
consent to their child’s participation in the study.
Haug et al. BMC Public Health (2018) 18:1102 Page 3 of 9
Within the first half of the information sessions in the
school classes, the junior scientist will raise awareness on
mands and challenges of everyday life. For this purpose,
they will use video sequences demonstrating typical
stressors and demands for this age group (e.g., search for
an apprenticeship, exam stress, peer pressure for substance
use) and different strategies to cope with them. The import-
ance of emotional regulation skills and social competences
to effectively cope with these stressors will be discussed
based on case vignettes. Subsequently, the students will be
informed about and invited to participate in a study testing
innovative channels for the provision of life-skills trainings.
To ensure sufficient participation and, thus, representative-
nessofthesample, a reward of 10 Swiss Francs for
participation in each of the two follow-up assessments will
Students (1) with minimum age 14, (2) who own a mo-
bile phone and (3) providing parental informed consent
will be invited to participate in the study. Using their own
or a provided mobile phone, informed consent will be ob-
tained online from the study participants. Subsequently,
they will be invited to choose a username, to provide their
mobile phone number and to fill in the baseline assess-
ment directly on the mobile phone.
Participants of the intervention group will receive add-
itional questions which are necessary for the tailoring of
the intervention content. Furthermore, for participants of
the intervention group, the mobile phone-based interven-
tion program and its association with a friendly competi-
tion will be described in detail. Subsequently, participants
of the intervention group will receive an individually tai-
lored web-feedback directly on their mobile phone (see
also section intervention). During the subsequent 6 months,
participants of the intervention group will receive the indi-
vidually tailored mobile phone-based life-skills training.
Participants of the assessment only control group will
be thanked for their study participation, they will be
Introduction in secondary school classes
by school class
Assessment of inclusion criteria
Follow-up assessment month 6
for 6 months
Minimum age 14, possession of a
mobile phone and informed consent
for study participation (students and
Follow-up assessment month 18
Fig. 1 Study design
Haug et al. BMC Public Health (2018) 18:1102 Page 4 of 9
informed about their group assignment and their reward
for participation in the follow-up assessment.
Follow-up assessments after 6 and 18 months will be
conducted by a research assistant, within the participat-
ing school classes, during regular school lessons and
using tablet computers. Computer-assisted telephone in-
terviews will be conducted by a research assistant when
assessments cannot take place during a school lesson be-
cause of vacations, class resolution, or study participants’
absence from class.
The study protocol was approved by the Ethics Commit-
tee of the Faculty of Arts and Sciences at the University
of Zurich (approval number 18.6.5; date of approval
June, 21st, 2018). The trial will be executed in compli-
ance with the Helsinki Declaration.
Randomisation and allocation concealment
To avoid spill-over effects within school classes, we will
conduct a cluster-randomised controlled trial using
school class as a randomisation unit. Due to the hetero-
geneity of students in the different secondary schools,
we will use a separate randomisation list for each school
(stratified randomisation). Furthermore, to approximate
equality of sample sizes in the study groups, we will use
block randomisation with computer generated randomly
permuted blocks of 4 cases .
Junior scientists supervising the baseline assessment
will be blinded to the group allocation of school classes.
In addition, group allocation will not be revealed to par-
ticipants until they had provided their informed consent,
username, mobile phone number, and baseline data. Fur-
thermore, the research assistants who perform the
computer-assisted follow up assessments for primary
and secondary outcomes will be blinded to the group
Sample size calculation
As this is the first study on the efficacy of a mobile
phone-based life-skills training for substance use preven-
tion, we could not rely our calculations on conclusive re-
sults of similar studies. Instead, our calculations were
based on the effect sizes of traditional face-to-face deliv-
ered life skills training programs in educational settings.
However, to account for the longer duration and higher
intensity of traditional life-skills trainings compared to
our mobile phone-based training, these estimates based
on the effect sizes of traditional face-to-face delivered
life skills training programs were revised downwards,
resulting in a more conservative estimation.
An estimation of the expectable effect sizes was based
on the results of a Cochrane Review on school-based pro-
grammes for preventing smoking  and on the efficacy
of a program for the prevention of binge drinking in ado-
lescents based on the Life Skills Training . The
Cochrane Review revealed a statistically significant effect
in preventing the onset of smoking for combined social
competence and social influences curricula (six RCTs)
with an Odds Ratio of 0.49 (95% CI 0.28–0.87). The pro-
gram for the prevention of binge drinking in adolescence
based on the Life Skills Training revealed an intervention
effect on problem drinking at the 1-year follow-up, with
an odds ratio (OR) of 0.41 (95% CI 0.18–0.93), and at the
2-year follow-up with an OR of 0.40 (95% CI 0.22–0.74).
Based on these studies, and a slight downward correction,
an OR of 0.60 was expected for the main outcome
Based on an estimated OR of 0.60 and an expected
30-days-prevalence of problem drinking in 16 year-old
adolescents of 25% in the control group at the 18-month
follow-up (mean of prevalence in 15-year olds derived
from HBSC study  and in 17-year olds derived from
Addiction Monitoring ), a sample size of n=370 in
each study group would be required to have 80% power
for a χ
-test (α= 5%, 2-sided) in order to detect this dif-
ference based on a calculation using G-Power.
Based on an estimated OR of 0.60 and an expected
30-days prevalence of tobacco smoking in 16 year-old
adolescents of 22% in the control group at the 18-month
follow-up (mean of prevalence in 15-year olds derived
from HBSC study  and in 17-year olds derived from
Addiction Monitoring ), a sample size of n=410 in
each study group would be required to have 80% power
for a χ
-test (α= 5%, 2-sided) in order to detect this
As secondary school students are nested within school
classes, we additionally need to consider a potential de-
sign effect for the calculation of the sample size for our
study. Based on [26,32], an average cluster size of 13
study participants per school class and an intra-cluster
correlation coefficient of 0.05 could be expected. This
would result in a design effect of 1.60. Multiplying this
design effect by the required size for an unnested sample
(n= 410) results in a required sample size of n= 656 per
study group and a total of n= 1312 study participants.
Thus, based on the participation rates of the previous
MobileCoach studies [32,33] and the pre-post study on
a mobile phone-based life- skills training, approximately
100 secondary school classes are required to reach this
Theoretical background and intervention contents
The intervention elements of the program will be based
on the Social Cognitive Theory [18,19]. This theory re-
lies on the Social Learning Theory, as it was founded on
principles of learning within the human social context
Haug et al. BMC Public Health (2018) 18:1102 Page 5 of 9
, though it has also integrated several concepts from
cognitive psychology. Key concepts of this theory, which
will be addressed within the mobile phone-based pro-
gram are (1) outcome expectations (i.e., beliefs about the
likelihood and impact of the consequences of behav-
ioural choices), (2) self-efficacy (i.e., beliefs about one’s
personal ability to perform a desired behaviour which
could be stimulated, for example, by mastery, experience
or persuasion); (3) observational learning (i.e., learning
new behaviours via exposure to them through interper-
sonal or media displays; e.g., through peer modelling);
(4) facilitation (i.e., providing strategies, tools, and re-
sources that make new behaviours easier to perform);
and (5) self-regulation (i.e., controlling oneself via moni-
toring, goal-setting, feedback, and self-instruction).
The contents of the mobile phone-based program will
rely on proven and widely-disseminated life-skills pro-
grams, like IPSY , ALERT  and Life Skills Train-
ing . The program addresses (1) self-management
skills, (2) social skills, and (3) substance use resistance
skills. The program will be structured according to these
major contents with the individually tailored web-based
feedback and the mobile phone text messages in weeks
1–9 focusing on self-management skills, the messages in
weeks 10–15 focusing on social skills, and the messages
in weeks 16–20 focusing on substance use resistance
skills. Boosters for each of the components will be pro-
vided in weeks 22–24.
The intervention program will be developed using the
MobileCoach system. Technical details of the system are
described elsewhere [34,35]. The MobileCoach system
is available as an open source project on http://www.mo-
bile-coach.eu. Password protection and Secure Sockets
Layer (SSL) encoding are used to ensure the privacy and
safety of data transfer.
Individually tailored feedback
The individual tailored web-based feedback will be given
to study participants of the intervention group immedi-
ately after completion of the online baseline assessment
within the school classes. This feedback comprises 4–5
screens, including textual and graphical feedback on
stress in general, the individual level of stress in various
domains compared to an age- and gender-specific refer-
ence group, and individual applied and suggested coping
strategies. The feedback will use individual data gathered
at the baseline assessment on perceived stress in differ-
ent domains (school, leisure time, friends, family, and
social media) and on individual strategies for coping
with stress. Instruments for the assessment of stress and
coping strategies will be derived from the study Juvenir
4.0, a national survey on stress in adolescents with more
than 1500 participants . Data of this survey will also
be used to provide an age- and gender-specific feedback
on the individual stress level.
For a period of 6 months, program participants will re-
ceive between two and four individualized text messages
per week on their mobile phone. These messages will be
generated and sent by the fully-automated system.
Within the first 9 weeks, the messages will focus on
self-management skills; e.g., coping with stress, emo-
tional self-regulation or management of feelings of anger
and frustration. In weeks 10–15, the messages will focus
on social skills; e.g., making requests, refusing unreason-
able requests, meeting new people. In weeks 16–20, the
text messages will focus on substance use resistance
skills; e.g., recognizing and resisting media influences,
social norms of substance use or the associations of
self-management skills and social skills with substance
use. Boosters for each of the components will be pro-
vided in weeks 22–24. The messages will be tailored ac-
cording to the individual data from the baseline
assessment and on text messaging assessments during
program runtime; e.g., on substance use or the individ-
ual’s emotional state.
To exploit the full potential of current mobile phones,
several interactive features, like quiz questions, tasks to
create individually-tailored if-then behaviour plans based
on implementation intentions, and message contests,
will be implemented within the program. Due to the
wide dissemination of smartphones in adolescents ,
several messages will also include hyperlinks to audio
files (e.g., audio testimonials, motivational podcasts), as
well as to thematically-appropriate video clips, pictures
and related websites.
Tabl e 1shows a selection of the planned intervention el-
ements, which are based on concepts derived from social
cognitive theory [18,19] and the major contents of
widely-disseminated life-skills programs [11–13]:
self-management skills, social skills, and substance use re-
To stimulate active program engagement, program
use will be associated with a friendly competition,
which will allow program users to collect credits for
each interaction (e.g., answering monitoring text mes-
sages, participating in quizzes, creating messages or
pictures within contests, accessing video links inte-
grated in text messages). The more credits partici-
pants will collect, the higher their chances will be of
winning one of several attractive prizes which will be
part of a prize draw (10 prizes with the sum of 500
Swiss Francs) after program completion. Participants
Haug et al. BMC Public Health (2018) 18:1102 Page 6 of 9
will be able to retrieve their number of credits com-
pared to the number of credits of other program par-
ticipants’of their group (similar starting date) at any
time from an individual profile page.
Assessments and outcomes
At baseline, demographic variables (age, sex, migra-
tion background), data on mobile phone use as well
as characteristics of the schools (location, type of
school) and school classes (level, size, number of stu-
dents present) will be assessed.
Baseline- and follow-up assessments will include
(1) Problem drinking in the preceding 30 days,
assessed by the short form of the Alcohol Use
Disorders Identification Test, the AUDIT-C .
This test comprises 3 items on (1) frequency of
alcohol consumption, (2) quantity of alcohol con-
sumption, and (3) binge drinking. Pictures will be
used to illustrate the quantity of a standard
drink, which corresponded to 12–14 g of pure al-
cohol. Based on a validation study of a large Ger-
man sample, a cut-off of ≥5 will be used .
(2) 30-days point prevalence rate for smoking
abstinence (“not having smoked a puff”within
the past 30 days according to the criteria of the
Society for Nicotine and Tobacco Research ).
(3) Quantity of cigarettes smoked in the preceding
30 days by assessing the number of smoking days
and the typical number of cigarettes smoked per
(4) Cannabis use in the preceding 30 days assessed by
an item of the HBSC study  addressing the
number of cannabis consumption days.
(5) Perceived stress assessed by a four-item version 
of the Perceived Stress Scale . This scale mea-
sures the degree to which students appraised situa-
tions as stressful over the preceding month.
(6) Interpersonal competences, assessed by the brief
version of the Interpersonal Competence
Questionnaire , addressing the following
domains of social competence: (1) initiation of
relationships, (2) negative assertion, (3) disclosure
of personal information, (4) emotional support, and
(5) conflict management.
The primary outcomes of the planned study are (1)
prevalence of problem drinking in the preceding 30 days
according to the AUDIT-C and (2) prevalence of
cigarette smoking in the preceding 30 days (having
smoked at least a puff according to the criteria of the
Society for Nictotine and Tobacco Research ).
Secondary outcomes are
Prevalence of cannabis use in the preceding 30 days
(having used cannabis at least once)
Quantity of alcohol use in the preceding 30 days
Quantity of cigarettes smoked in the previous
Table 1 Exemplary intervention elements of the mobile phone-based life-skills training
Self-management skills Social skills Substance use resistance skills
Individually tailored information on pros of using self-management
skills to cope with stress.
Tailored information on the
pros of applying social skills,
e.g., making requests.
Information on pros of
resisting alcohol, including
social norms within an age-
and gender-specific reference
Self-efficacy Videos demonstrating easily applicable strategies to cope with
Contest on creating a bubble
text on refusing an
unreasonable request within a
given situation presented on a
Creation of if-then-plan for
resisting invitation for smok-
Interactive message contest on stress regulation strategies. Video showing exemplary
behaviour on individually
poorly developed social skills.
Video podcast showing peer
models who successfully
refused cigarette smoking.
Facilitation Creation of if-then-plans for coping with the currently most severely
affecting stress situation.
conversational skills or
strategies for making requests.
Contest on creating a bubble
text on refusing an alcoholic
drink at a party presented on
a given picture.
Self-regulation Monitoring of and feedback on individual emotions. Monitoring of and feedback on
progress of individual social
Monitoring of and feedback
on individual alcohol use.
Haug et al. BMC Public Health (2018) 18:1102 Page 7 of 9
Frequency of cannabis use in the preceding 30 days
Generalized Linear Mixed Models will be used to test
intervention effects for binary outcomes and linear
mixed models for continuous outcomes [43,44]. These
models account for both fixed and random effects and
are particularly useful in analysing longitudinal and
nested data (e.g., time within students, students within
school classes). To test the efficacy of the intervention,
we will test the variables “study group”,“time”and their
interaction “study group x time”as predictors of the out-
come criteria assessed at follow-up. If necessary, we will
control for baseline differences by adding additional
baseline variables as covariates to the models. We will
conduct both (1) intention to treat analyses and (2)
complete case analyses considering all study participants
with available follow-up data. For ITT analyses, we will
use multiple imputation procedures as described else-
Substance use in adolescents and later adulthood and its
related consequences represent a serious public health
problem . Although life-skills trainings were effective
in preventing the onset and escalation of both problem-
atic alcohol and tobacco use [7,11,30], the implementa-
tion and dissemination of the existing programs in
schools represent serious challenges as they require large
resources in terms of money and time . In contrast
to comprehensive school-based curricula, training and
counselling via mobile phone is more economic and
matches with the lifestyle and communication habits of
the target group. Most adolescents are familiar with how
to use mobile phones and typically use them on a daily
basis for texting, taking photos, playing games etc. This
is the first study testing the efficacy of a mobile
phone-delivered life-skills training for substance use pre-
vention among adolescents within a controlled trial.
Given that this program proves to be effective, it could
be disseminated to various groups of adolescents, e.g. in
schools or leisure time settings. A translation of the
intervention content into other languages would easily
enable program dissemination to adolescents in other
regions and countries.
AUDIT-C: Short form of the alcohol use disorders identification test
We would like to thank Andreas Filler and Tobias Kowatsch for their
technical assistance in using the MobileCoach platform for this project.
Funding for this study is provided by the Swiss National Science Foundation
(No. 10001C_179222/1). The funder has no role in study design, data
collection and analysis, decision to publish, or preparation of manuscripts.
Availability of data and materials
SH and RPC were responsible for the study design. SH, RPC, MPS, and AW
designed the mobile phone-based intervention program. SH and RPC are re-
sponsible for the data collection. All authors read and approved the final
Ethics approval and consent to participate
The study protocol was approved by the the Ethics Committee of the
Faculty of Arts and Sciences at the University of Zurich (approval number
18.6.5; date of approval June, 21st, 2018).
The parents of the secondary school students in participating classes are
asked to give written informed consent to their child’s participation in the
study. Students providing parental informed consent will be invited to
participate in the study. Using their own or a provided mobile phone,
informed consent will be obtained online from the study participants.
Consent for publication
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
Received: 3 August 2018 Accepted: 14 August 2018
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