Condition category
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting

Plain English Summary

Background and study aims
In Denmark, as well as in most Westernized countries, smoking is now more prevalent among adolescents from lower socioeconomic positions (SEP). Only eight percent of 15-year old Danish adolescents from higher social classes smoke daily or sometimes, whereas up to 37% of adolescents whose parents live from welfare benefits are smokers. Furthermore, adolescents from low SEP seem less likely to quit smoking in adulthood. Programmes addressing health and health behaviour in childhood or adolescence have the potential to prevent or decrease socioeconomic inequalities in health behaviours later in life, and public health interventions to reduce risk behaviours e.g. smoking, should aim at being equally effective across socioeconomic groups, or at being especially effective among individuals from low socioeconomic position. In order to develop effective interventions which work across social groups, it is important to study the social patterning of the effect of intervention methods. The X:IT I study was a school- based study to prevent smoking among 13- to 15-year old students targeting all students. The X:IT I study was the first large-scale Danish smoking intervention to be effective in reducing uptake of smoking in adolescents in Denmark. The qualitative process evaluation found that the X:IT I study did not reach students and parents from low social classes. Therefore, all X:IT I materials have been revised and specifically directed at adolescents and parents from lower social classes and at those who might have academic challenges. The aims of this study include: investigate the social patterning of the implementation and effects of the X:IT I study, based on the knowledge acquired from the X:IT I study, develop and implement a smoking intervention especially focusing on adolescents and parents from low socioeconomic background, the X:IT II study and to conduct scientific process and effect evaluations of X:IT II including studies of social differences in the implementation and effects.

Who can participate?
Students in grade seven, eight, and nine (aged 13 years to 15 years).

What does the study involve?
All schools receive the same programme. X:IT II include three main intervention components: smoke-free school grounds, parental involvement comprising two dimensions including smoke-free contract between the pupil and an adult person, preferably a parent and smoke-free dialogues, and finally a smoke-free curriculum based on self-efficacy training and outcome expectancies. Students from high and low social classes are compared in a difference-in-difference design.

What are the possible benefits and risks of participating?
Participants may benefit from the benefits of not smoking with prevention of the well-known risks of smoking. There are no direct risks of participating, although some indirect risks can be mentioned such as being marginalized if you are a smoker and the psychosocial consequences of this.

Where is the study run from?
This study is being run by the National Institute of Public Health University of Southern Denmark (Denmark) and takes place in schools in Denmark.

When is the study starting and how long is it expected to run for?
January 2017 to July 2020

Who is funding the study?
The Danish Cancer Society (Denmark)

Who is the main contact?
Mrs Anette Andersen

Trial website

Contact information



Primary contact

Mrs Anette Andersen


Contact details

University of Southern Denmark
National Institute of Public Health
Øster Farimagsgade 5A
+45 65507879



Additional contact

Mrs Lotus Sofie Bast


Contact details

University of Southern Denmark
National Institute of Public Health
Øster Farimagsgade 5A
+45 65507809



Additional contact

Prof Pernille Due


Contact details

University of Southern Denmark
National Institute of Public Health
Øster Farimagsgade 5A
+45 65507880

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

The X:IT II Study - A Smoking Intervention aimed at adolescents from low social class background



Study hypothesis

1. The X:IT intervention material, carefully developed to take into account the intellectual skills and academic performance of adolescents’ and their parents’, will improve the reach of the intervention among low SEP
2. The X:IT study will have an overall effect of a 25% reduction in smoking uptake at age 13
3. The X:IT study will reduce smoking uptake among low SEP adolescents to the same extent or more than among adolescents with a high SEP background

Ethics approval

There is no formal institution for ethical assessment and approval of questionnaire-based population studies in Denmark. When inviting the schools to participate, headteachers received written information about the study. Students and their parents were informed about the study. They were informed that participation was voluntary, that their information would be used for research purposes only and treated confidentially. The study is registered at the Danish Data Protection Agency, ref: 17/53093.

Study design

School-based intervention study

Primary study design


Secondary study design

Non randomised study

Trial setting


Trial type


Patient information sheet


Smoking prevention


The X:IT intervention includes three main components:

1. Completely smoke-free school grounds for both students and teachers during school hours and other school-related events. Law on Smoke-free institutions was given in Denmark in 2012. The literature showed that higher levels of perceived enforcement of anti-smoking policy at the school level were inversely associated with the prevalence of past-30-day smoking behaviors among students. Therefore, the intervention also includes enforcement of this law.
2. Parents are to be involved in two ways – by signing a smoke-free contracts between the student and an adult person, preferably a parent, each year for all three intervention years (in grad 7, 8, and 9), and by conducting smoke-free dialogues with the child. By signing a smoke-free contract the adolescent promises to stay smoke free for the next year. Signing the contract is a manifestation of an active choice of non-smoking. One of the parents or another adult co-signs the contract. With the contract, the signatory promises to conduct a smoke-free dialogue with the adolescent and to support the adolescent’s choice of staying smoke-free. Having a smoke-free dialogue involves that the parent clearly takes exception to adolescent smoking, asks the child about thoughts about and experiences with tobacco. This kind of constructive communication has shown to be effective. The adolescents are motivated to make a personal choice, and engaging the parents communicates a clear opposition to adolescent smoking. Students remaining smoke-free for one year are able to win a prize.
3. A smoke-free curriculum based on self-efficacy training and outcome expectancies is supposed to take place at school for at least 8 hours each year for three years. The literature showed that information-giving curriculum incorporated in multi-modal programs seem to be successful. Programs based on social influence approaches, including aspects like:
3.1. Correcting adolescents’ perceptive overestimation of the smoking prevalence
3.2. Recognizing high-risk situations
3.3. Increasing awareness of media, peer, and family influences
3.4. teaching and practicing refusal skills
5.3. Making public commitments not to smoke more effective.
The teaching program for the X:IT intervention was developed based on the above awareness. The actual educational material, “Gå op i røg” (Up in Smoke), was developed in conjunction with scholars who had educational experience. The teachers can choose methods of teaching as well as supplementary exercises and materials. The material targets students, 13 to 15 years of age. It is designed to be used in diverse subjects such as science, humanities and social science. Goals in the National Executive Order of Education can be fulfilled by using the material.

Smoke-free contracts are provided to the students at school to bring home for signing with a parent. Copies can be downloaded here: A webpage designed for the parents with inspiration for these talks are available. The webpage has four entrances, one with general information, one for parents who smoke themselves, one for parents with smoking children, and one for parents and children who wants to learn more about smoking:
All materials for teaching, including detailed information for teachers, are available online :

Smoke-free school grounds: enforcement must be discussed at the school board.
Smoke-free curriculum: a school coordinator must keep track of what and how much each school-class has been taught. The individual teachers in the diverse subjects must deliver the actual teaching.
A one-day work-shop to initiate the intervention is held for head-teachers, school coordinators, and teachers.

The teaching is provided during school hours either as 2-hour sessions or as workshop days.The intervention takes place at local public or private schools in Denmark. Smoke-free contracts will be signed once a year for three years (year 7, 8, and 9). The smoke-free curriculum has to take place for at least 8 hours each year for three years (year 7, 8, and 9)

The intervention is for all students and parents. As smoking is more prevalent in low social class, the educational material and parent information is developed and designed to secure that all groups will be reached.

Implementation fidelity will be assessed by four domains: adherence, dose, quality of delivery, and participant responsiveness according to the theory by Dusenbury et al (2003). Questionnaire data obtained from students and teachers will be used.

Intervention type



Drug names

Primary outcome measure

1. Frequency of smokers at grade seven, eight and nine measured at baseline, 1,2 and 3 follow-up by student self-reported questionnaires
1.2. Frequency of smoking will be analyzed at individual, class and school level, and stratified by gender and socioeconomic level
2. Degree of implementation after first, second, and third year of intervention by student self-reported questionnaires and project coordinator questionnaires

Secondary outcome measures

Intermediate outcomes of the intervention:
1. Individual outcomes:
1.1. Enhanced self-efficacy for smoking
1.2. Increased knowledge about smoking
1.3. Change in norms and attitudes towards smoking
1.4. Performed smoke-free dialogue with parents
2. Group level outcomes
2.1. Increased probability of smoke-free environments at home and at schools
2.2. Changed norms and attitudes against smoking at schools
2.3. Reduced availability of tobacco
2.4. Increased probability of not being exposed to smoking students, teachers and parents
Analyses in the project will have a special focus on subgroup analyses especially gender and socioeconomic position.
3. Sustainability
3.1. At second follow-up it will be measured whether participation in Project X:IT has initiated environmental changes and capacity building by questionnaires to project coordinators at schools and in municipalities. Furthermore, we will measure whether the project continues at intervention schools and is initiated at control schools.
4. Differences in frequency of drunkenness and marijuana use between intervention and control schools
5. Differences in students’ wellbeing between intervention and control schools

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

All students at participating schools enrolled in grade 7 (age 13 years to 15 years).

Participant type


Age group




Target number of participants

60 clusters (schools), around 50 students grade 7 in each school

Participant exclusion criteria

Schools for children with special needs.

Recruitment start date


Recruitment end date



Countries of recruitment


Trial participating centre

National Institute of Public Health, University of Southern Denmark
Øster Farimagsgade 5A

Sponsor information


University of Southern Denmark

Sponsor details

National Institute of Public Health
Øster Farimagsgade 5A
+45 65507777

Sponsor type




Funder type


Funder name

The Danish Cancer Society

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

The following publications are planned in a high-impact peer reviewed journals:
June 2018: Design paper X:IT II
December 2018: Paper on process evaluation
June 2019: Paper on differential effects after year 1
June 2019: Paper on differential implementation after year 1
December 2019: Paper on school differences in implementation
December 2020: Paper on differential effects after year 3
December 2020: Paper on differential implementation after year 3

IPD sharing statement:
The data sharing plans for the current study are unknown and will be made available at a later date.

Intention to publish date


Participant level data

To be made available at a later date

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes