Figure 1 shows the flow diagram mapping the number of records selected, included and excluded. The search carried out in PubMed retrieved 2361 articles, and the screening of the 2361 titles and abstracts was carried out by one reviewer (JM). After the first screening, 273 studies were selected and read by one reviewer (JM), leaving 6 studies which met the selection criteria. In this process the entire article was read revealing that the majority of the preselected studies described interventions which also included late childhood or adolescents or took place outside Europe and were therefore excluded. A second search was performed in IBSS which retrieved 4747 articles. The first screening of the titles and abstracts was carried out by one reviewer (JM). After the first screening, 159 studies were selected and read by one reviewer (JM), leaving 5 studies which met the selection criteria, for the same reason as described above. Four reports describing various early childhood interventions were retrieved from the grey literature. Two presented information on interventions which met our abovementioned selection criteria and two were excluded as there was not sufficient specific information on the evaluation. Finally twelve interventions published in the grey literature were selected.