A personality disorder (PD) or character disorder is a type of disorder where a person thinks, feels and behaves differently from how society expects them to. Where these traits would be flexible in most people, these traits are rigid and unworkable in someone with a personality disorder and create lasting patterns and often lasting problems. These thoughts, feelings and behaviours can cause problems for the person, and for other people around them. In the United States, the United Kingdom, and many other countries, personality disorders are classed as a kind of mental disorder and are treated by medical professionals. About ten percent of adults have PDs. They are often caused by child abuse and trauma.

Types
In the Diagnostic and Statistical Manual of Mental Disorders, a book about mental illness written by the American Psychiatric Association, there are ten personality disorders. They are split into three "clusters" or groups.

Cluster A
Cluster A is the odd or eccentric group of personality disorders. They have similarities with schizophrenia.  They are:
 Paranoid personality disorder: These people do not trust others. They believe that others are trying to ruin their life.
 Schizoid personality disorder: These people like to stay alone. They do not enjoy most things and do not show much emotion. 
 Schizotypal personality disorder: These people have weird beliefs and are very afraid of other people.

Cluster B
Cluster B is the dramatic or emotional group of personality disorders. They are:
Antisocial personality disorder: These people tend to bully others. They do not care about people or the law. Around three percent of men and one percent of women have ASPD.
Borderline personality disorder: These people have unstable relationships, self-image and moods. They are very impulsive. Around one percent of men and three percent of women have BPD.
Histrionic personality disorder: These people are very emotional and need to be the center of attention. They are flirtatious and seductive. Around one percent of men and four percent of women have HPD.
Narcissistic personality disorder: These people think that they are better than other people. They boast about themselves and need other people to look up to them. They use other people to achieve their goals. Around one percent of people have NPD.

All Cluster B disorders are comorbid with each other. There are things that are in more than one PD. For example, selfishness and lack of empathy are major parts of ASPD and NPD. Needing to be admired is a major part of HPD and NPD.

Cluster C
Cluster C is the anxious or fearful group of personality disorders. They are:
 Avoidant personality disorder: These people avoid close relationships because they feel worse than other people. They have a high amount of social anxiety and feel terrible when criticized. 
 Dependent personality disorder: These people seek the affection of other people. They often cannot make decisions on their own.
 Obsessive-compulsive personality disorder: These people do not relax. They are often very busy.

ICD
The World Health Organization has a different way of describing personality disorders. It makes use of the International Statistical Classification of Diseases and Related Health Problems (ICD).

The specific personality disorders are: paranoid, schizoid, dissocial, emotionally unstable (borderline type and impulsive type), histrionic, anankastic, anxious (avoidant) and dependent in the current version. The current version is the ICD-10.

Related pages 

 Mental Illness
 Psychology
 Psychiatry

References