For 40 years, the Big Five personality model has dominated psychology, but new research suggests it may be incomplete.

Alexander Christensen's recent study probably won't rewrite 40 years of history in the field of psychology, but he hopes that ...

Antisocial personality disorder is a type of chronic mental illness in which a person's ways of thinking, perceiving situations, and relating to others are abnormal—and destructive.

Borderline personality disorder is a complex diagnosis characterized by difficulties in mood regulation. Some individuals with borderline personality disorder suffer from a bipolar disorder as well.