The characteristics that make up a personality disorder vary for each type of personality disorder, but can generally be broken down into three 'clusters'. While these clusters describe many common personality traits, a person is only diagnosed with a personality disorder when these traits are excessive and cause distress or interrupt day-to-day life.
Cluster A
Cluster A consists of personality disorders where behaviour is seen as odd or erratic:-
Paranoid Personality Disorder. The individual believes without any proof that someone or a group of people are planning to deceive or hurt them.
Schizoid Personality Disorder. This disorder is characterised by indifference and a reluctance to engage with other people.
Schizotypal Personality Disorder. A person with schizotypal personality disorder will avoid social interactions and will often have abnormal beliefs about the world that might be supernatural or magical.
Cluster B
Cluster B personality disorders tend to show behaviours that are emotionally erratic or dramatic:-
Borderline Personality Disorder (BPD). Someone with this disorder will often have an overwhelming fear of being abandoned and will have difficulty controlling their moods (especially anger). They will also often have very unstable moods, perception of the self and relationships.
Anti-social Personality Disorder. Someone with anti-social personality disorder will often be deceitful, aggressive, impulsive, reckless and irresponsible. They also tend not to feel sorry for any harm they've caused to others
Histrionic Personality Disorder. A person with this disorder will often act very dramatic, theatrical, and seductive. They may feel unhappy unless they are the centre of attention and their emotions may shift quickly, but may not be very deep.
Narcissistic Personality Disorder. Someone with narcissistic personality disorder will feel a sense of grandiosity, that they are special and a need for admiration from others. They might take advantage of others and not feel guilty afterwards.
Cluster C
Cluster C personality disorders tend to involve fear and anxiety:-
Dependent Personality Disorder. Someone with this disorder will feel an excessive need to be taken care of and will find being alone and doing things without help very difficult.
Obsessive-Compulsive Personality Disorder (OCPD). A person with OCPD will be very concerned with orders and routines and will feel anxious if these are broken. They tend to be so concerned with doing things right, that they don't have time to do any fun activities.
Avoidant Personality Disorder. Someone with avoidant personality disorder will often feel inadequate and will be very sensitive to criticism. They will often feel very worried about what others think of them, and may not interact with others to avoid any criticism.