Objective: To examine the extent to which identification of any distinct personality characteristics in bipolar subjects are influenced by selection of the comparison diagnostic group.
Method: Scores were compared on several general measures of personality style and, additionally, the prevalence of disordered personality functioning was examined in a sample of 198 non-psychotic depressed subjects, 39 with bipolar depression and 159 with unipolar depression.
Results: When the bipolar subjects were separately compared with unipolar subjects, and to sub-sets of those with clinically and DSM-IV defined melancholic and non-melancholic depression, quite differing results were suggested. In essence, clinically-defined melancholic subjects had the least personality psychopathology in comparison with the non-melancholic and bipolar subjects.
Conclusion: Whether subjects with bipolar disorder have any distinct personality characteristics or over-represented co-morbid personality disorders remains quite unclear when reference is made to the literature. We suggest that inconsistencies across studies may reflect choice and representation of depressive sub-types within the unipolar comparator group.