I understand that these relations are based on some sort of notion of "evidence" via scientific studies. My question would be - there seems to be a rather low amount of studies per relation in most cases, how is the specific study that establishes a relation here chosen? In reality, in many fields we often see completely contradictory studies, e.g. in psychology or nutrition.

Example: I saw there is a relationship between "rural area" and "major depressive disorders", "established by 1 source": https://www.system.com/view/topic-relationship/wdlsYqXAGFc/j...

Is there really just one study about this? What would happen if there was one study saying that there is such a relationship, and one saying there isn't?

To me it seems that this kind of system leads to a weird simplified spaghetti view of the world, which at best might be an ok topic explorer, but at worst almost like a conspiracy theory automator (following the threads of more or less representative studies of things being "related").