Personality disorders are a mix of negative expectations based on life experiences and inner rules for dealing with those expecations that don't work well, as far as I can see. They DO overlap, I have read it is rare for anyone to be a "pure type".

Different people will try different ways of coping with a stressor, so one type of stressor could lead to different ways of coping which psychology labels Dependent, Avoidant, and so on. For example, Avoidant and Borderline have self-discrepancy in common (ie., seeing ourselves as not measuring up to whom we want to be) as well as high rejection sensitivity.

What complicates the whole concept of personality disorders further is that many people have some component of them, and these disorders themselves are "spectrum disorders", so someone could be extremely Avoidant, a little Dependent, moderately Borderline, and so on. The disorders themselves are just an attempt to organize a bunch of related negative self-concepts, expectations and coping mechanisms into a framework that can be studied. As such, they are a bit oversimplified.

For example, I meet diagnostic criteria for Avoidant Personality Disorder, yet I don't avoid people anywhere near as much as some Avoidants do. I also can relate to SOME aspects of Dependent and Borderline, but I don't have enough of those traits to have those disorders. Google the name Theodore Millon, he's a psychologist who has proposed subtypes for each of the recognized personality disorders. These subtypes seem to nicely explain the overlap between personality disorders.

Here's some interesting info for you:

* http://en.wikipedia.org/wiki/Avoidan...ality_disorder
* http://en.wikipedia.org/wiki/Hikikomori (Hikikomori is a Japanese equivalent of AvPD; check out the contributing factors, especially social and cultural stressors, I suspect many people can relate!)
* http://en.wikipedia.org/wiki/Borderline_personality_disorder#Millon.27s_subtypes
* http://en.wikipedia.org/wiki/Depende...n.27s_subtypes
* http://en.wikipedia.org/wiki/Self-Discrepancy_Theory
* http://www.psychologytoday.com/artic...03/am-i-normal

I'm going to share what I've learned about myself in the hopes it will help you. After a lot of work, I've found that I have a huge fear of not being accepted (based on life experiences), which has made self acceptance difficult. Apparently I have buried this fear as a defense mechanism. Assertiveness and self-confidence have been reduced as a result. I have high self-discrepancy because I see myself acting less confident than I want to, and didn't quite understand why until recently. Therefore, I get frustrated and angry at myself and end up being self-rejecting. This is the process which for me causes things like procrastination, social anxiety, self-doubts, loneliness and depressive episodes. The most accurate label I have found for this process is Millon's "Avoidant Personality Disorder with self-deserting characteristics", and that is assuming I really understand what he's writing about.

I hope this helps you.