Personality disorders are defined as maladaptive patterns of behavior that begin in adolescence and continue into adulthood, causing emotional and relationship problems. There are three clusters of personality disorders: Cluster A includes paranoid, schizoid, and schizotypal disorders; Cluster B includes borderline, histrionic, and antisocial disorders; and Cluster C includes avoidant, dependent, and obsessive-compulsive disorders. Personality disorders are treatable through therapies like dialectical behavior therapy, mentalization-based treatment, psychodynamic therapy, and schema therapy which help patients understand maladaptive beliefs and behaviors and replace them with healthy coping strategies.