Every one of us has our own personality that describes who we generally are. This is often how we organize our sense of self and our impressions of the people around us. Personality disorders,  however, describe a form of psychopathology marked by extreme, rigid personality difficulties that can cause impairment (in multiple domains) for the individual. Moreover, they can cause a multitude of interpersonal difficulties for those around them. In this chapter we review one of the more popular theories of personality – the Five Factor Model – and discuss the differences between personality and personality disorders.

The DSM-5 organizes personality disorders into three clusters, based on their common characteristics. Cluster A personality disorders involve odd and eccentric thinking or behaviour, and include paranoid, schizoid, and schizotypal personality disorder. Cluster B personality disorders involve dramatic, overly emotional or unpredictable thinking or behaviour, and include antisocial, borderline, histrionic, and narcissistic personality disorder. Cluster C personality disorders are marked by anxious, fearful thinking or behaviour and include avoidant, dependent, and obsessive-compulsive personality disorder.

Personality disorders are, unfortunately, some of the most challenging disorders to treat. This is because they are so entrenched, chronic, and pervasive for the people who experience them. Very few people with personality disorders present for treatment, and if they do it is often because they are experiencing social/occupational impairment or because someone else has pushed them to go. The exception is borderline personality disorder, which is quite distressing for those who experience it. Our treatment development for personality disorders lags behind that of other disorders, although there is one empirically supported treatment for borderline personality disorder: Dialectical Behaviour Therapy.