Background:
Personality traits have been proposed as potential endophenotypes for genetic studies of psychiatric disorders. One personality theory that demonstrates strong heritability is Cloninger's seven-dimensional psychobiological model assessed by the temperament and character inventory (TCI). We aimed to determine how individuals with bipolar disorder differ from individuals with major depression (MDD) and unaffected relatives of patients with bipolar disorder using the TCI.
Methods:
Data were collected from 277 adults recruited in Christchurch, New Zealand, as part of the South Island Bipolar Study. The 240-item TCI questionnaire was used to determine personality profile, and the diagnostic interview for genetic studies was used to establish four groupings, bipolar disorder type 1 (BP1), bipolar disorder type-2 (BP2), MDD and nonaffected relatives. Differences identified with an ANOVA were corrected for current mood state by the inclusion of the Beck Depression Inventory as a co-variate in a univariate ANOVA.
Results:
Total harm avoidance was higher and self-directedness was lower than controls in all mood disorder groups but not different between them. Total self-transcendence was higher in BP1 than MDD and unaffected relatives. Correction for current mood influenced the significance of the differences between groups.
Conclusions:
The TCI has identified commonalities and differences between bipolar disorder and MDD. Higher harm avoidance and lower self-directedness may reflect personality markers of mood disorders, whereas high self-transcendence appears to be specific to bipolar disorder. Self-transcendence may prove to be a useful measure for the investigation of the genetic basis of bipolar disorder.
