Personality disorders are characterized by enduring patterns of behavior that deviate from cultural norms. They are grouped into three clusters - A, B, and C. Cluster A disorders include paranoid, schizoid and schizotypal personality disorders. Cluster B includes antisocial, borderline, histrionic and narcissistic disorders. Cluster C comprises avoidant, dependent and obsessive-compulsive personality disorders. The disorders are generally stable over time and can lead to unhappiness and impairment.