Complex sentence: When the DSM-IV was created and Major Depressive Disorder was spelled out more clearly, there still seemed to be a range of depression where one did not have full blown Major Depression, but still was undoubtedly depressed.
Split into simpler sentences: When the DSM-IV was created and Major Depressive Disorder was spelled out more clearly, there still seemed to be an uncategorized range of depression. People in this category did not have full blown Major Depression, but still were undoubtedly depressed.