I wouldn't say that asexuality/non-sexuality is necessarily a product of mental health issues. I knew long, LONG before I got fucked up that I wasn't into boinking at all, the same way one would know flat-out that they're not into fucking animals. I've had boyfriends that I've broken up with and suitors I've turned down purely because I realized that a 'boyfriend' was no different than a 'best friend' for me (though my definition of 'best friend' is likely a LOT deeper than most). I understood that that was going to be a fundamental issue going forward since that's a major difference for most people, with physical intimacy being VERY important to the relationship. It's not that I was sexually abused or traumatized. It's not that I'm into girls. I've never been religious nor is my family oppressively so. And I've never been on anything beyond OTC aspirin, allergy meds, or antibiotics.
The thought of making a family, having a significant other and children, appealed to me when I was younger. But the actual MAKING the baby part? A complete turn-off that would completely nuke that desire at the slightest thought. Pregnancy doesn't spook me. Childbirth doesn't spook me. It's the act, itself. It disgusts me. Why? Well, 99% of it is because it's unhygienic. Same goes for kissing, oral, and all that jazz. I'm fully aware of how silly that sounds and that that's how I got here, but I want no part of it, myself. I wouldn't call myself a germophobe: I'm usually the only one on staff that has the stomach to thoroughly clean the damn bathrooms, meanwhile my own room's a fucking mess. And I have no problem with other people partaking in it; it's just gross when I'm personally involved. Outside of blood, bodily fluids make me gag.
The other 1% is that I just fucking hate dealing with people at this stage.
TMI, but I will admit that I masturbate (probably no more or less than your average person) and do have turn-ons, namely of ideas/concepts rather than physical traits. Spergy, I know, but that's the only way I can describe it. And when I'm having my 'fun time', only ONE particular way will end in success, if you catch my drift. Anything else results in nothing but boredom. I even thought at one point that I really, REALLY wanted a different sensation and got a vibrator that I can keep all clean and sanitary. Nope; just a waste of time and money.
Now that I think about it, 'non-sexual' might not be the right word for it, either. I'm still very straight: The thought of snuggling with a man appeals to me and I have a preferred type, but with a woman I fluctuate between apathetic and repulsed. ...But that's probably because women are generally bitches and constantly piss me off on top of having next to nothing in common with me.
At the end of the day, a specific label isn't really necessary. I have no desire to fuck; simple as that.
Just a bit of explanation from a resident 'non'.
All that demi- and gray-asexual shit needs to go, though. That constant bullshit contest to be the MOST SPECIAL-EST EVAR is why I left AVEN behind.