Yes, we have brain chemicals that can cause a variety of mood swings and sometimes you can feel grumpy, and then the release of an endorphin by hard exercise or a good laugh can make you feel elated. I'm assuming that's the "ice" effect that you're referring to.
Falling estrogen and progesterone levels can trigger mood swings and set off depressive episodes and it's easy to understand why a person might feel grumpy or depressed, but less easy to understand what drives them to commit such horrific crimes against children. I don't know if there's proof that brain chemicals can cause such abhorrent behaviour, but if they can, what triggers their release?
However, my main point was that dismissing such horrifically evil behaviour as simply due to "a lack of love" is ludicrously facile.
