A personality disorder is what happens when someone is so fucked up as a child, a really small child, that they are unable to develop normally. The stages of personality development that we all pass through from mewling infant to autonomous adult are disrupted in someone with a personality disorder. This is not due to any innate problem with their brains, with the possible exception of antisocial personality disorder a.k.a. psychopathy, it is almost entirely due to having abusive parents. There is simply no getting around this. Sorry. It’s the parents’ fault.
The fucked up child becomes stuck at an early stage of personality development. Usually this stage is one that would normally passed through before the child is 5 years old or so. Due to the disordered nature of the child’s interactions with their parents they cannot progress beyond a certain stage and this immature mental age stays with them for their entire life causing no end of problems in their interactions with other human beings.
Children frozen at the Little Nero temper tantrum stage of development grow up narcissistic. Those who mature a little further and have learned some more socially acceptable strategies to get their own way develop histrionic personality disorder. Those who get frozen just as they reach out to take some ownership of their environment and the wider world develop anxious disorders. This freezing doesn’t mean the person acts like a child. The problem is far more profound than simply being about behaviour.
The person with a personality disorder is unable to understand other human beings. Just like a two year old truly doesn’t understand notions such as love, justice or sharing so the adult frozen at the emotional age of a two year old grows up fundamentally unable to understand these ideas. They see other people as a child would see them. As objects which move around and interact, providing for their needs or not but without having much clue about the other people’s inner life and motivations.
Theory of mind is the ability to attribute mental states such as intent, knowledge, desire, belief, to oneself and others and to understand that others have beliefs, desires, and intentions that are different from one’s own. People with personality disorders never developed a full theory of mind. So they are frozen with emotional needs and a theory of mind at a debilitatingly early stage.
On top of this immaturity is another layer of problems. When your very survival in the form of being adequately fed, cared for and nurtured as a small child depends on some people who themselves are not very mentally healthy you have to develop strategies pretty damn quick to make sure your unhealthy mum and dad don’t either attack you physically or emotionally or neglect you.
The defence strategies of a child in an abusive environment take several forms. There is defence in the form of managing their emotions. For example you may learn very early on not to cry as no one will come to comfort you, you may learn showing anger with the unhealthy parents is seriously disapproved of and so never raise your voice or look irritated. You may learn that showing fear delights the unhealthy parent and so present a completely neutral face even when terrified.
There is defence in the form of people-pleasing. You may learn that doing whatever your unhealthy parents want straight away gets you a quieter, nicer life. There is defence in adopting dysfunctional communication methods like triangulation, proxy recruitment or passive-aggressive ways of conveying messages. The most damaging defence however is to copy the unhealthy adults. That way the child ends up being abusive, not just receiving abuse. These defences against being abandoned and rejected by the unhealthy mum and dad remain frozen in the person with a personality disorder long after they have served their purpose.
So there is a double whammy; being mentally stuck at a really very immature stage in their way of being able to conceptualise other people and having developed and retained some very dysfunctional ways of relating to other people.
This is a pattern of behaviour that is with the personality disordered person their whole life and is evident from adolescence onwards. It is a pattern of behaviour that is sufficiently damaging so that it interferes with the career, relationships, family and daily function of the individual. It is not the result of a short term life event or source of stress such as bereavement or illness and is not, in the main, treatable. Bummer.