BACKGROUND: Studies show a high and growing prevalence of mental disorders in the population worldwide. 25% of the general population in Europe will during their lifetime experience symptoms related to a mental disorder. The Mental Health First Aid concept (MHFA) was founded in 2000 in Australia by Kitchener and Jorm, in order to provide the population with mental health first aid skills. The aim of the concept is, through an educational intervention (course), to increase confidence in how to help people suffering from mental health problems. Further, secondary aims are to increase the mental health literacy of the public by increasing knowledge, reduce stigma and initiate more supportive actions leading towards professional care. An investigation of the effect of MHFA offered a Danish population is needed.

METHODS: The design is a randomized waitlist-controlled superiority trial, in which 500 participants will be allocated to either the intervention group or the control group. The control group will attend the course six months later, hence waiting list design. From fall 2013 to spring 2014 participants will be educated to be "mental health first-aiders" following a manualized, two days MHFA course. All the participants will answer a questionnaire at base-line and at 6 months follow-up. The questionnaire is a back-translation of the questionnaire used in Australian trials. The trial will be complemented by a qualitative study, in which focus groups will be carried out.

DISCUSSION: Outcomes measured are sensitive to interpretation, hence a challenge to uniform. This trial will add to the use of a mixed-methods design and exemplify how it can strengthen the analysis and take up the challenge of a sensitive outcome.

TRIAL REGISTRATION: https://clinicaltrials.gov identifier NCT02334020.