Search	Key Word (KW) or Subject Heading (SH)	Terms	Results
#1	KW	“play” [all fields] OR “preten*” [all fields] OR “game*” [all fields] OR “toy” [all fields] OR “recreation” [all fields]	902,704
#2	SH/MeSH	“recreation” [MeSH terms] OR “play and playthings” [MeSH terms]	239,869
#3	KW	“train” [all fields] OR “trains” [all fields] OR “train set” [all fields] OR “train track” [all fields] OR “train play” [all fields] OR “Hornby” [all fields]	59,758
#4		1 OR 2	1,103,474
#5		4 AND 3	1215
#6		5 Filters: child birth–18 years	794
Note. For key words related to ‘Train’, the term ‘train*’ was not used as it resulted in many irrele-vant articles, largely related to the term ‘training’. Subject headings/MeSH terms in PubMed were different to those used in PsycInfo due to database differences, and an analogous term for ‘railroad trains’ did not exist. * reflects truncation of the search term.