I have the feeling I'll regret participating in that discussion very soon, but I'll give it a try.
I think a lot of "mental issues" are based on our past. You make experiences, they shape your instincts. Most often that happens unconsciously. This happens everyday and it's very hard to identify why we react in ways that we react and even harder to attempt to reflect on that and develop new experiences so we instinctively behave to circumstances in the way we want to behave.
I also think that infants are very influencable and learn fast from their surroundings. So if you as a kid are around a person that shows anxiety you're more likely to duplicate instincts that point to danger when there's no real threat around. That's why I think these kind of situations happen in some families more often than in others.
I'm also no big fan of medication over a longer tenure unless absolutely necessary. I know there's cases where this is inevitably but in normal cases(I know that each case is unique and yet we're always making categories and comparing) I think it's key to combine medication with therapy so you actually use the medication to alter your habits and get new experiences while closing with the old/ill advised ones.
I liked what dalamon wrote earlier about the genetic-expression. I don't know if you're a biologist or whatever but the way you wrote about it it seemed like you know a thing or two about it. And I also think it mixes well with my psychological view of how you develop yourself as a person through experiences.
It's also one of the reasons I like sports as much as I do I think:
It's where you have a very visible environment where you can watch genes meet psychology and math. Things I'm interested in and I feel I'm naturally good at(The last two of course just to prevent accusations that I view myself as a superman with super genes)
I wanna close with a disclaimer that this is my view and when I used generalizing terms they only reflect my views. I didn't do any extra research on that topic, just wrote based on my own experiences and the knowledge shared with me on that field of expertise by professionals.