Aha!

This page describes me perfectly: http://www.mind.org.uk/help/diagnoses_and_conditions/paranoia
I don't have hallucinations, obviously, but am forever fearful of what people are going to say or do.

Excerpt:
Being paranoid means being suspicious without reason, and believing that others are trying to harm you in some way....
...people who are prone to paranoia always dread some forthcoming attack or betrayal. They are forever anticipating that something awful will happen, and trying to second-guess what their adversaries might do.

.... It can be a very isolating condition, because people feel they can't depend on anybody. They may feel angry, fearful, guilt-ridden, suspicious, vengeful and excluded, and may become very depressed, as a result.

end Excerpt

And what are the causes of paranoia? They *think* it might have something to do with genetics, at least in part. But genetics alone doesn't lead to paranoia.

Among other causes, here are the ones that apply to me:-

What happens to us in childhood may play a part. If a child is brought up to believe that the world is a very unsafe place and that people are horrible, this may mould their personality in a paranoid direction. Self-esteem, or lack of it, is also important. If children are not brought up to feel that they are basically lovable, they may be suspicious or mistrustful when others show them affection. It's thought that very grandiose behaviour or a highly inflated sense of importance, which paranoid people sometimes show, can be an unconscious compensation for such feelings

I am in danger of practicing plaigiarism if I reproduce any more of the article here. I've tried to reproduce less than 10% which I think doesn't count as plagiarism, with credits. But so much of it rings true.

Treatment usually includes administering small doses of anti-psychotics. This is precisely what happened to me. It is disheartening to note here that despite knowing my full history and, in particular, my paranoid mindset, even the particular withdrawal symptoms, a well recommended psychiatrist could not work out why a previous doctor had put me on rispiridone. He said give it up, don't even bother to taper down, just give it up. This caused a huge depressive incident and this is after I told him this had happened to me before when I tried to withdraw!

Basically, good mental health care is extremely difficult to find.