Perhaps you should try some spelling variations:
"helped decrease" » "helped decreased" (Expand Search), "helped increase" (Expand Search)
"helper decrease" » "helper decreased" (Expand Search), "helper increase" (Expand Search)
"mean decrease" » "mean decreased" (Expand Search), "mean increase" (Expand Search)
"greater decrease" » "greater decreased" (Expand Search), "greater increase" (Expand Search)

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"helped decrease\") OR (\"helper decrease\"))) OR (((\"mean decrease\") OR (\"greater decrease\"))))~".
• Removing quotes may allow a broader search: (((( helped decrease ) OR ( helper decrease ))) OR ((( mean decrease ) OR ( greater decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (((("helped decrease") OR ("helper decrease"))) OR ((("mean decrease") OR ("greater decrease"))))*.