Yes, but not much. The heavier spines are usually a little denser and physically heavier as well. Keep in mind, though, that you need to match the spine of the arrow to the draw weight of the bow. Trying to shoot heavy spined arrows our of a light weight bow will not yield good arrow flight.
If you're looking for more strength, you might consider going to a different wood. Doug fir is stronger than Cedar of the same diameter and spine. Likewise, the hardwoods, ash, maple, hickory, birch, etc. are much stronger than cedar and even Doug fir in the same spine and shaft diameter.