Personality disorder signifies deeply rooted and persistent behavioural patterns that are inflexible and hinder the adaptation to various circumstances and situations in life. In the DSM-IV, personality disorders are classified into three main clusters. - Cluster A: paranoid, schizoid and schizotypal personality disorders. These persons often appear odd or eccentric. - Cluster B: antisocial and narcissistic personality disorders. These persons are often dramatic, impulsive and emotionally unstable. - Cluster C: avoidant, dependent and obsessive-compulsive disorders. These persons are often anxious or phobic.