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)
"greater decrease" » "greater decreased" (Expand Search), "greater increase" (Expand Search)
"mean decrease" » "mean decreased" (Expand Search), "mean 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 (\"greater decrease\"))))) OR (\"mean decrease\"))~".
• Removing quotes may allow a broader search: (((( helped decrease ) OR ((( helper decrease ) OR ( greater decrease ))))) OR ( mean decrease ))~.
• Adding a wildcard symbol may retrieve word variants: (((("helped decrease") OR ((("helper decrease") OR ("greater decrease"))))) OR ("mean decrease"))*.