A personality disorder is a type of mental disorder in which a person thinks, behaves, and perceives things differently from the norm. The patterns of thoughts and behaviors of a person with personality disorder are unhealthy and inflexible. They often have difficulties understanding relationships and situations which cause problems at work and home.
According to the ICD-10, specific personality disorders "are severe disturbances in the personality and behavioral tendencies of the individual; not directly resulting from disease, damage, or other insult to the brain, or from another psychiatric disorder; usually involving several areas of the personality; nearly always associated with considerable personal distress and social disruption; and usually manifest since childhood or adolescence and continuing throughout adulthood."
Personality disorders include paranoid personality disorder, schizoid personality disorder, dissocial personality disorder, emotionally unstable personality disorder, histrionic personality disorder, anankastic personality disorder, anxious personality disorder, and dependent personality disorders among others.