A lot of studies are like this. They build on existing ideas and push the boundaries in a very specific direction. Here they show that adding a forest floor env

A lot of studies are like this. They build on existing ideas and push the boundaries in a very specific direction. Here they show that adding a forest floor environment to a kindergarten will increase certain immune related markers in the blood of the children playing there. They managed to design the study so that you can’t say “oh, but children playing in kindergartens close to forests probably don’t live in cities, so they probably don’t get exposed to as much pollution”. Other studies will find links between those immune related markers and the development of autoimmune related disease, or someone will do a statistical analysis on kids that grew up in kindergartens close to forests to see if their incidence of autoimmune related disease is lower.