Acknowledgements
The authors would like to thank Dr Bartomeu Castanyer Puig, Dr Santiago Nogué Xarau and Dr Carlos Campillo Artero for their critical advice. The support of the Coordinació Autonòmica de Drogues de la Conselleria de Salut de les Illes Balears and the Observatorio Español sobre Drogas del Ministerio de Sanidad, Politica Social e Igualdad to our research group is also acknowledged.
Disclosure statement
The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.
Funding information
This work was supported in part by a grant from the Fondo de Investigación Sanitaria (PI12/00283), Instituto de Salud Carlos III, Ministerio de Educación y Ciencia, Spain.