Looking through the files again. For some reason I can't find a json file for CON. Normally, traits are under \Data\Effects\States with the name trait_{name}.json, and there is one for every relevant one - except for CON. As far as I can see, it raises HP by 1, stamina by 2.5, and each sex attack stat by 0.5.
I am curious about that because the Nympho trait might actually be a trap. It applies a multiplier to stamina and sexy, both of which have no effect on the actual sex attack stats while locking you out of HQ weapons or magic for no good reason.
See, since you actually have to option to chose mouth sex when juicing, you could use the Succubus as a an alternative to Alchemy to replenish your food on the way while trading better traps for higher stamina. I am currently testing the practicability of a neutral character that mildly invests into Constitution and then dumps the rest into Combat or Wisdom. If my hypothesis is right, it will actually perform just as well as a Nympho in sucking the opponents dry while having access to HQ weapons.