Studying personality characteristics in bipolar depressed subjects: how comparator group selection can dictate results.
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.


METHODS
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.


CONCLUSIONS
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.
Parker
G
G
School of Psychiatry, University of New South Wales, and Mood Disorders Unit, Black Dog Institute, Prince of Wales Hospital, Randwick, New South Wales, Australia. g.parker@unsw.edu.au
Parker
K
K
Malhi
G
G
Wilhelm
K
K
Mitchell
P
P
D000328:Adult; D001714:Bipolar Disorder / Q000175:diagnosis* / Q000453:epidemiology*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D008297:Male; D010554:Personality Disorders / Q000175:diagnosis* / Q000453:epidemiology*; D010555:Personality Inventory; D015995:Prevalence; D012720:Severity of Illness Index