This study evaluates the short- and long-term effects on psychological wellbeing and health-related behaviours of the updated version of a universal school-based program called Diario della Salute (DDS-2) in Italian students aged 11-13 years.

The updated version of Diario della Salute (DDS-2) is a universal school-based intervention aimed at promoting psychological and emotional well-being and preventing unhealthy and risky behaviours (cigarettes smoking, alcohol abuse, unhealthy eating habits, physical inactivity) in preadolescence. The program is composed by 5 highly standardized interactive units delivered by previously trained teachers during school hours on emotional and social issues related to developmental tasks in adolescence. The kit includes: 1) a teacher's manual, 2) a booklet for each participating student, 3) a booklet for parents of each participating student. The objective is to promote and reinforce adolescents' emotional and social skills as factors contributing to adolescent well-being and health.

A randomised controlled trial with two parallel groups is performed, with 1:1 allocation ratio, in two different Regions of Italy (Piedmont and Veneto). Schools are randomly assigned to one of the two groups (DDS-2 intervention vs. no intervention) and are used as the unit of allocation. Individual participants (i.e. students) are the unit of analysis. Schools are matched by number of students and average socioeconomic status. Eligible schools are identified from the list of all schools having students from 11 to 13 located in study sites. A number of eligible schools accounting for the requested number of students in the target grades is invited to participate in the study. If a school does not respond to the invitation or declines to participate, the school recruitment process is repeated, and another eligible school is invited to participate. The process continues until achievement of the sample size. No incentive is offered to students, families and schools for participating in the study.

A paper-and-pencil self-report anonymous questionnaire developed by the research group is used to determine whether the interventions have changed the outcomes. The questionnaire will be administered in classes by the researchers at baseline, at the end of the intervention and one-year after the end of the intervention (at equal intervals both in the intervention and in the control group). The questionnaire consists of the following sections: 1) demographics, 2) emotional and social skills, 3) psychological wellbeing, 4) school experience, 5) unhealthy and risky behaviours, 6) prosocial and aggressive behaviours. Questionnaires are linked through an anonymous self-generated code.

Inclusion Criteria:

1. public/government schools,
2. at least two classes attended by students aged 11-13,
3. not participating in other school-based programs with similar objectives targeted to the classes of interest,
4. providing consensus to study participation. In participating schools, all classes of students aged between 11 and 13 years are eligible to be enrolled in the study.

Exclusion Criteria:

1. private schools,
2. less than two classes attended by students aged 11-13,
3. involved in other school-based programs with similar objectives targeted to the classes of interest. In participating schools, students whose parents opt out from the study are excluded.