I m sure the phrase medically unexplained symptoms goes back a lot farther than the 70s it s an easy enough series of words to put together in a medical setting But we can t build an article about a random phrase so the question becomes When was it used to indicate a specific category of illnesses I have no idea if Slavney was the first to do so or not but I think that we re confounding the phrase with an actual category A common phrase is probably not notable by Wikipedia standards a medical category might be if it s in wide use So I think we need to identify when this phrase was first coined to refer to a category of illnesses and prove that it s actually noteworthy Without an entry in DSM IV or a similar medical reference the notability of the concept really needs to be shown Also as someone else said somewhere if it is considered a medical category somewhere we need to identify if it s primarily a psychiatric psychological concept or a broader one Similarly I think we re also confounding the category with related terms like somatoform disorder and functional somatic symptoms Unless the source itself says that in that particular text they re intended to mean the same thing any assumption that another text is making the same assumption would be synthesis