I've read up on as much psychology research on this as I have been able to find. The problem is that it isn't a lot. Very little research has been done on the roots of masochism. On the other hand there's been a little more research on "how to cure this mental affliction of masochism". Which today is pretty dated in how we view sexual fetishes.
We do know that our brain is super effective at drawing conclusions based on flimsy evidence. It's built/evolved for speed in dangerous situations and not for correctness in pondering the big questions. We really can't draw the conclusion, "I am a masochist" and "I was abused" therefore "the abuse made me a masochist".
The mental back-flip here is that it assumes a healthy or natural starting point of our sexual desires which doesn't include masochism or kinks. Nobody has been able to find such a person. All our sexual needs are extremely complex.
Not to get too deep here, but the Western philosophical tradition we inherited from Plato starts with the assumption that we're faulty, (since we live in the land of the mortals) and that perfection/harmony/health can be attained if we rid ourselves of something holding us back or perhaps we're permanently broken by some damage earlier in our lives. In Plato's day mental perfection could be found among the Gods. This thinking still permeates our culture completely. Christians even think it's some kind of virtue to accept this original sin. Scientologists identify the negative energy as extra terrestrial parasites. New Ager's babble on about attaining harmony constantly without any deeper thought about what it means.
There is off course no such thing as the the mind in harmony. Or some kind of enlightened state of eternal bliss. Or even state of total mental health. Or let me rephrase that. No scientist has been able to find any brain that doesn't have some sort of easily identified pathology. We have a culture revolving around beating ourselves up for mental short-comings. Just stop. Don't try to find the act that was the root of it, because you'll most likely simplify it too much or just simply be wrong.
The word de jour is "biologism" or "biological determinism".
http://en.wikipedia.org/wiki/Biologism
This is the trend right now, and more and more research is piling up to prove it right. If it swings back to behaviourism time will tell. But it's looking pretty bleak for their camp today.
What modern science are saying on this issue seems to indicate that, if you're born with a submissive brain in our culture you're more likely to get abused by those who identify your submissiveness and take advantage of it. In other words. Nothing and nobody makes you through their actions submissive.
The ability to enjoy being beaten is linked to how much endorphins your brain releases when pain is inflicted. Nothing complicated and very easy to understand. No magic. There's nothing you can do with your brain to change this. This is simply the brain you're born with. Yes, you're more likely to discover this "ability" early in life if you where beaten as a kid. And that's a good thing. But you can't acquire the liking of this purely physical feature by early abuse. That's just not how our brains work.
But the field of psychology has a very far way to go when it comes to research in this. They don't like to do research in a field where they won't discover something that needs years of therapy to cure. It's not in their professional interest. And all the limited research seems to indicate that masochism and submissiveness is not something we acquire as the result of something being broken.