http://paizo.com/pathfinderRPG/prd/mastery/sanityAndMadness.html
When using a spell, such as major curse, to inflict someone with an insanity, which DCs should I use for the initial save, and the saves to cure it? That which is listed under the insanity's description, or the spell DC?
I would go with whatever is higher.
You'd use the one listed under the specific insanity they contracted since the insanity is a separate effect from the spell that cast it.
Though the insanity is now also a curse and it could be dispelled by remove curse using the spells DC.
That's kind of what I was thinking too, but there doesn't seem to be much of anything supporting that interpretation.
It also kind of makes for a weak 6th-level spell if the DCs don't truly scale.