The area of personality disorders is a sensitive one. Many people find this type of diagnostic labeling pejorative, judgmental, or insulting. And there are examples I have seen where professionals have applied such labels to patients in a pejorative, judgmental, or insulting manner.
Some of the professional literature on this subject is almost impossibly pedantic or arcane.
Yet on the other hand, personality disorder categories do describe the experiences of life many people have been through, or are continuing to go through.
Some of my patients readily accept the idea of having a "personality disorder", and have worked earnestly and successfully with their symptoms, using this type of diagnostic framework.
I am cautious myself about using "personality disorder" terminology. Yet I acknowledge that sometimes understanding, and speaking frankly about, these issues, permits opportunities for things to get better more efficiently and quickly.
In general I would say that "personality disorders" could be understood as collections of chronic symptoms and behaviours which have had strong, recurrent, entrenched feedback cycles involving a person's experience of relationships with other people, with society, with work, and with lifestyle. The intersection of symptoms with these relationships tends to lead to negative results, then tends to perpetuate the pattern. And this dynamic persists irrespective of whether there are prominent mood or anxiety symptoms.
In chronic psychological conditions of any type, whether it be depression, anxiety, psychosis, etc., there are similar intersections between symptoms and relationships, but my sense of the dynamic in personality disorders is that the relationship and lifestyle disruption persists independent of other psychological symptoms.
In some cases, chronic primary symptoms such as anxiety, depression, irritability, or mood lability, could cause "personality disorders" to arise, particularly if such symptoms have been present since early childhood.
Another frequently-observed or theorized cause for "personality disorder" phenomena is childhood adversity or trauma. The adversities or traumas may differ, but in most cases recurrent or ongoing trauma is most strongly associated. Different types of adversity may affect people with different inherited temperaments in different ways -- the same type of trauma may severely affect one person, while causing few lasting symptoms in another.
It is clear that, just as with most any other set of psychiatric symptoms or diagnoses, there is a significant inherited predisposition to have a "personality disorder" diagnosis. Heritability estimates are typically in the 40-50% range. To some degree these types of findings have always seemed obvious to me, it confirms that most anything that happens in life is jointly a product of genes and environment, and the proportional split of causality is often about 50/50.
Advancing understanding of this issue has led to a conceptual shift: "personality disorders" need not be considered lifelong ailments or "defects of character". It is clear that all types of psychological symptoms may change or improve with time, under the right conditions.
There are numerous categories of "personality disorder" as described in the DSM-IV and other diagnostic schemes, and in future posts I would like to discuss each of them in turn. Also there are different theoretical schemes about what "personality" even means--and I think the best research in this area shows that personality itself is better-described using categories quite different from those in the DSM-IV. Yet, I find the DSM-IV categories do describe a common variety of problems and experiences which many of my patients have been through, and so I do think that they have relevance and validity.