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

Plain English Summary

Background and study aims
Although the harmful effects of tobacco have been known for many years, we have not succeeded in preventing young people from taking up smoking. Many young people still start smoking, and the number of young smokers has only decreased slightly during the last 10 years. Starting smoking at age 15 increases your risk of becoming a daily smoker as an adult. Therefore, it is very important to prevent smoking among children and young adolescents. The aim of this study is to develop and test a school-based anti-smoking program to reduce the number of smokers by 25% over a three-year period.

Who can participate?
Students in grade 7 at the start of the study

What does the study involve?
Participating schools are randomly allocated to either the intervention group or the control group. Students at the intervention group schools receive the anti-smoking program, whereas students at the control group schools do not. The anti-smoking program has three main components: eight anti-smoking lessons a year; students sign a contract promising to stay smoke free for the next year; and no smoking is allowed on the school premises. Furthermore, the study includes workshops for the staff, newsletters for the schools, a website with guidelines for parents and information for schools, and presentation of the study at parent school meetings each year. The study runs for three years (grade 7-9), with an annual follow-up in the spring of each year to measure how many students smoke.

What are the possible benefits and risks of participating?
The schools receive free educational materials and free workshops introducing the study and later sharing experiences of the study. Furthermore, participating schools receive a report describing the health behaviours of the adolescents in their school. The students among other things increase their knowledge about the risks of smoking, the social factors influencing decisions to smoke or not, and the role of the media in adolescent smoking. All students who stay smoke-free for a year have the chance to win a prize. There are no known risks to participants.

Where is the study run from?
Centre for Intervention Research in Health Promotion and Disease Prevention at the National Institute of Public Health, University of Southern Denmark

When is the study starting and how long is it expected to run for?
January 2010 to June 2013

Who is funding the study?
1. The Danish Cancer Society (Denmark)
2. Centre for Intervention Research in Health Promotion and Disease Prevention (Denmark)

Who is the main contact?
Anette Andersen

Trial website

Contact information



Primary contact

Mrs Anette Andersen


Contact details

Øster Farimagsgade 5A
+45 (0)65 50 77 77

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

X:IT - a three-year multi-component, school-based, cluster randomized trial to reduce smoking among 13-15 year olds in Denmark



Study hypothesis

To reduce prevalence of smokers by 25% over a three-year period, at grade 9 in intervention schools compared to control schools.

Ethics approval

There is no formal institution for ethical assessment and approval of questionnaire-based population studies in Denmark. The study is registered at the Danish Data Protection Agency, 15/04/2010, ref: 2010-54-0930

Study design

Cluster randomized controlled design with three-year follow-up

Primary study design


Secondary study design

Cluster randomised trial

Trial setting


Trial type


Patient information sheet

Patient information can be found at (Danish)




Students in grade 7, 8 and 9 at 51 intervention schools receive the X:IT intervention program during the school years 2010/11, 2011/12 and 2012/13, whereas students at 43 control schools do not receive any intervention. The intervention lasts for three school years, e.g. from August 2010 till May 2013. Baseline data was collected August 2010, first follow-up survey May/June 2011, second follow-up survey May/June 2012 and third follow-up survey May/June 2013. The intervention focuses at three arenas/levels which influence adolescents’ lives:
1. Parent involvement
1.1. Students and parents sign a smoke-free contract each year for three years
1.2. Parents are encouraged to undertake a smoke-free dialogue with their child each year for three years
2. Smoke free curriculum, 8 lessons every year for three years with new teaching materials, for more information see
3. Smoke free schools throughout the intervention period. Information for municipalities, schools and parents are available on

Intervention type



Drug names

Primary outcome measures

1. Frequency of smokers at grade seven, eight and nine measured at baseline, 1,2 and 3 follow-up by student self-reported questionnaires
1.1. Measures of smoking will be supplemented by analyses of number of cigarettes smoked and age at debut
1.2. Frequency of smoking will be analyzed at individual, class and school level

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. Increase probability of smoke-free environments at home and at schools
2.2. Changed norms and attitudes against smoking at schools
2.3. Reduce availability of tobacco
2.4. Increase 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


Participant inclusion criteria

All students at participating schools enrolled in grade 7 at baseline (August 2010)

Participant type


Age group




Target number of participants

4.468 students (2538 in the intervention group, 1930 in the control group) at 51 intervention schools and 43 control schools from 17 municipalities cross nationally

Participant exclusion criteria

1. Schools not run by municipalities
2. Schools for children with special needs

Recruitment start date


Recruitment end date



Countries of recruitment


Trial participating centre

Øster Farimagsgade 5A

Sponsor information


Centre for Intervention Research in Health Promotion and Disease Prevention (Denmark)

Sponsor details

National Institute of Public Health
University of Southern Denmark
Øster Farimagsgade 5A
+45 (0)65 50 77 77

Sponsor type




Funder type


Funder name

Kræftens Bekæmpelse

Alternative name(s)

Danish Cancer Society

Funding Body Type

private sector organisation

Funding Body Subtype

other non-profit



Funder name

Center for Intervention Research in Health Promotion and Disease Prevention (Denmark)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Results - basic reporting

Publication summary

2014 protocol in:
2016 results in:

Publication citations

  1. Protocol

    Andersen A, Bast LS, Ringgaard LW, Wohllebe L, Jensen PD, Svendsen M, Dalum P, Due P, Design of a school-based randomized trial to reduce smoking among 13 to 15-year olds, the X:IT study., BMC Public Health, 2014, 14, 518, doi: 10.1186/1471-2458-14-518.

Additional files

Editorial Notes

19/09/2016: Publication reference added. 11/08/2016: Plain English summary added.