Despite various methodological schemas designed to categorize personality disorders, many issues occur with classifying a personality disorder because the theory and diagnosis of such disorders occur within prevailing cultural expectations; thus, their validity is contested by some experts on the basis of inevitable subjectivity. They argue that the theory and diagnosis of personality disorders are based strictly on social, or even sociopolitical and economic considerations. Classification and symptoms
The two latest editions of the major systems of classification are

the International Classification of Diseases (11th revision, ICD-11) published by the World Health Organization
the Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition, DSM-5) by the American Psychiatric Association.The ICD is a collection of alpha-numerical codes which have been assigned to all known clinical states, and provides uniform terminology for medical records, billing, statistics and research. The DSM defines psychiatric diagnoses based on research and expert consensus. Both have deliberately aligned their diagnoses to some extent, but some differences remain. For example, the ICD-10 included narcissistic personality disorder in the group of other specific personality disorders, while DSM-5 does not include enduring personality change after catastrophic experience. The ICD-10 classified the DSM-5 schizotypal personality disorder as a form of schizophrenia rather than as a personality disorder. There are accepted diagnostic issues and controversies with regard to distinguishing particular personality disorder categories from each other. Dissociative identity disorder, previously known as multiple personality as well as multiple personality disorder, has always been classified as a dissociative disorder and never was regarded as a personality disorder.
In a study comparing 100 healthy individuals to 100 borderline personality disorder patients, analysis showed that BPD patients were significantly more likely not to have been breastfed as a baby (42.4% in BPD vs. 9.2% in healthy controls). These researchers suggested this act may be essential in fostering maternal relationships. Additionally, findings suggest personality disorders show a negative correlation with two attachment variables: maternal availability and dependability. When left unfostered, other attachment and interpersonal problems occur later in life ultimately leading to development of personality disorders. Genetics
Currently, genetic research for the understanding of the development of personality disorders is severely lacking. However, there are a few possible risk factors currently in discovery. Researchers are currently looking into genetic mechanisms for traits such as aggression, fear and anxiety, which are associated with diagnosed individuals. More research is being conducted into disorder specific mechanisms. Neurobiological correlates - hippocampus, amygdala
Research shows that several brain regions are altered in personality disorders, particularly: hippocampus up to 18% smaller, a smaller amygdala, malfunctions in the striatum-nucleus accumbens and the cingulum neural pathways connecting them and taking care of the feedback loops on what to do with all the incoming information from the multiple senses; so what comes out is anti-social - not according to what is the social norm, socially acceptable and appropriate. Management
Specific approaches
There are many different forms (modalities) of treatment used for personality disorders:
Individual psychotherapy has been a mainstay of treatment. There are long-term and short-term (brief) forms. Family therapy, including couples therapy.