Perhaps you should try some spelling variations:
"complicated diseases" » "complicated cases", "complex diseases"
"mediated diseases" » "related diseases", "medical diseases"
"complicated case" » "complicated cases", "complicated acute", "complicated chapter"
"related disease" » "related diseases"

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (((("complicated diseases") OR ("complicated case"))) OR ((("mediated diseases") OR ("related disease")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"complicated diseases\") OR (\"complicated case\"))) or (((\"mediated diseases\") or (\"related disease\"))))".
• Removing quotes may allow a broader search: (((( complicated diseases ) OR ( complicated case ))) or ((( mediated diseases ) or ( related disease )))).
• Adding a wildcard symbol may retrieve word variants: (((("complicated diseases") OR ("complicated case"))) or ((("mediated diseases") or ("related disease"))))*.