This is a really interesting topic, and like SLP said unless you do a comprehensive study (which I doubt has ever been done fairly), our answers are only based on personal experience and theoretical speculation.
Still there are a lot of fundamental questions here that slip between the cracks. What exactly is depression anyway? I think it's an umbrella word for an array of human emotions that tend to get lumped together under a single label, and this causes a lot of confusion. Life is always changing and sometimes in the ebb and flow it's natural to get depressed, so I guess the ailment of "depression" refers to an irrational or supposedly unwarranted maladjustment to life or to oneself. How we view the disease and our bodies depends entirely on our assumptions about the world and ourselves. In ancient times they had depression, but they didn't have neuroscience or psychology in the way we understand things today. But they had treatments and cures. On the most basic level, we are collections of energy that have gathered somehow into the form and function that makes a human being. Our prosperity and sense of wellness is contingent on the free flow of this energy, like a river adapts to its environment. When something is blocked, or stuck, there is maladjustment, stagnation, or even violence (a dam bursting). Neuroscience and endocrinology can trace the cause and effect model of neurotransmitters and hormones and how they relate to our sense of well-being, but this basic pattern still holds.
I think there's a false depression that's a byproduct of our society. The vast majority of people with "depression" don't have anything wrong with them from their nature. We have the luxury of being lazy, and unhappy, and still being able to survive since we don't have to go through physical trials in order to eat or have shelter. Most people are forced to stick to the same routine to go to the same bullshit job with the same people for years - how could that NOT create depression and stagnate the person's growth as an individual? In general going out with friends, exercising, and having a healthy sex life balances it out and people get by, but when one of these is missing people feel stuck. I think BDSM is a great way for people with this kind of depression to overcome it and deal with their stress. It's an intense physiological event that can induce the same hormonal output as a fight or flight reaction, which will quickly end the tediousness of modern life.
Then there are people who are grieving over a tragedy. Then there are people who are coping with transition in their lives. Then there are women in menopause who are suffering from a shift in hormones that will pass in a few years. And then there are people who have been traumatically disturbed in their lives. Others maybe have a constitutional predisposition to it. There may be some people with emotional trauma that gravitate towards BDSM as a result of it, but to say it's a "prerequisite" isn't true because many of them don't, and many who like BDSM are normal functioning people. However, there might be some truth in the fact that people get used to being treated a certain way and may be stuck in a certain pattern of human interaction. A lot of women who are being physically abused protect their partners because they don't know any other way to be, and their minds have accepted it to be normal. This is the kind of person to watch out for that could be dangerous for the Dom since they are dangerous to themselves.
Speaking from personal experience, my girlfriend and I only get kinky when we're both feeling great. We haven't had any kink since she was hurt in a car accident because it's nurturing time and healing time, and I've put my feelings as a dom/top completely aside to be there for her. But she's highly strung by nature so as she gets back into the swing of things, I imagine she'll need a good spanking in no time
