Authors’ contributions The study was conceived and designed by MK, EP, PMH and KT. The data was acquired and collated by OR, IK, MK, SC and analysed by OR, IK, MK, GM, SC and KT. The study was drafted and revised critically for important intellectual content by all authors (OR, IK, GM, SC, MG, JN, HG, EP, PMH, KT, MK). All authors gave final approval of the version to be published and have contributed to the study. Article guarantor: Dr Maria Kyrgiou. No ethical approval required.