The DSM-IV-TR (2000) defines a personality disorder as:
"An enduring pattern of inner experience and behavior that deviates markedly from the expectations the individuals culture (and is manifested in two or more of his or her areas of mental life:) cognition, affectivity, interpersonal functioning, or impulse control."
Such a pattern is rigid, long-term (stable), and recurrent. It manifests itself in all areas of life (it is pervasive). It is not owing to substance-abuse or a medical condition (such as head trauma). It renders the subject dysfunctional "in social , occupational, or other important areas" and this impairment causes distress.
In the DSM, there are 10 distinct personality disorders (Paranoid, Schizoid, Schizotypal, Antisocial, Borderline, Histrionic, Narcissistic, Avoidant, Dependent, Obsessive-compulsive) and one catchall category, Personality Disorders NOS (Not Otherwise Specified).
Personality disorders with marked similarities are grouped into clusters.
Cluster A (the Odd or Eccentric Cluster) includes the Paranoid, Schizoid, and Schizotypal Personality Disorders.
Cluster B (the Dramatic, Emotional, or Erratic Cluster) is comprised of the Antisocial, Borderline, Histrionic, and Narcissistic Personality Disorders.
Cluster C (the Anxious or Fearful Cluster) encompasses the Avoidant, Dependent, and Obsessive-compulsive Personality Disorders.
The Clusters are not valid theoretical constructs and have never been verified or rigorously tested. They constitute merely a convenient shorthand and so provide little additional insight into their component personality disorders.
We start our tour with Cluster B because the personality disorders it includes are ubiquitous. You are far more likely to have come across a Borderline or a Narcissist or a Psychopath than across a Schizotypal, for instance.
First, an overview of Cluster B:
Borderline Personality Disorder is marked by instability. The patient is a roller-coaster of emotions (this is called emotional lability). She (most Borderlines are women) fails to maintain stable relationships and dramatically attaches to, clings, and violently detaches from a seemingly inexhaustible stream of lovers, spouses, intimate partners, and friends. Self-image is volatile, one's sense of self-worth is fluctuating and precarious, affect is unpredictable and inappropriate, and impulse control is impaired (the patient's threshold of frustration is low).
The Antisocial Personality Disorder involves contemptuous disregard for others. The psychopath ignores or actively violates other people's rights, choices, wishes, preferences, and emotions.
The Narcissistic Personality Disorder is founded on a sense of fantastic grandiosity, brilliance, perfection, and power (omnipotence). The narcissist lacks empathy, is exploitative, and compulsively seeks narcissistic supply (attention, admiration, adulation, being feared, etc.) to buttress his False Self - a confabulated "person" aimed at inspiring awe and extracting compliance and subservience from others.
Finally, the Histrionic Personality Disorder also revolves around attention-seeking but is usually confined to sexual conquests and displays of the histrionic's capacity to irresistibly seduce others.