: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.