One service call I get after a kitchen has been installed is customers noticing the crown molding that was up against the ceiling has dropped. In most cases, that is due to moisture drying up in the wood and shrinking.
Usually it takes a season or two to experience this. The wood used to build your cabinets and molding will be dried before manufacture. However, the wood still has the ability to take in moisture even after it has been cut.
Finished wood can take longer to take in moisture than unfinished wood. Therefore, the wood stud structure of your house will likely shrink faster and/or greater than the finished parts of your house.
For our seacoast area your house can show signs of shrinking during the winter and expanding during the summer. During our summer months is when moisture in the air is at its highest. So more likely than not that dropped crown molding will pick itself back up again during the summer.
The video below will give you a better understanding with regard to the effects of moisture in wood.