Funding for this research was provided by:
Ministerio de Economía y Competitividad (#PSI2013-4480-P)
Ministerio de Educación, Cultura y Deporte (#FPU13/05914, #FPU13/03315)
Text and Data Mining valid from 2018-09-12
First Online: 12 September 2018
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.
: All procedures performed in the study were in accordance with national and institutional ethical standards for research with human subjects and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The study was granted ethical approval from the Research Ethics Committee of Universidad Nacional de Educación a Distancia, Madrid, Spain. The study is registered at Clinicaltrials.gov (NCT03123991).
: All parents or guardians as well as adolescent participants provided written informed consent.