Damage over time destruction spells are more magicka efficient (i.e. shock 10 pts for 2 seconds costs less magicka than shock 20 pts for 1 sec). What I want to know is can the effects stack? Can I cast the same spell multiple times on an opponent and have the damage effects stack while it is still taking damage from the initial attack?

If you cast the same spell at them it will reset the spell. If you have multiple different spells they should stack just fine.

Cool thanks. I was really starting to wonder why it was so ineffective and then I had this epiphany, "Spells with the same name don't stack!"

Yep. You could make several spells that do the exact same thing. The name change is all it needs.

Yeah I always do that with feather spells.