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"))))))*.