Results from a Korean study show how personality trait patterns differ between patients with bipolar I and II disorder.
Yeon Ho Joo (University of Ulsan College of Medicine, Seoul) and team found that patients with bipolar II disorder (BD II) had significantly higher levels of neuroticism and lower levels of extraversion than those with bipolar I disorder (BD I).
"Further studies, including longitudinal assessments, are needed to determine how these personality traits are differentially linked with the etiology and clinical expressions of BD I and BD II," they write in Psychiatry Investigation.
The findings come from a study of 85 BD I (47 women) and 43 BD II (23 women) patients, aged between 18 and 65 years, who had been in a euthymic state for at least 8 weeks. The two groups were comparable in terms of gender distribution, age, education level, and socioeconomic status.
All of the participants were assessed using the NEO Personality Inventory (NEO-PI-R) - a 240-item measure of five personality dimensions (neuroticism, extraversion, openness, agreeableness, and conscientiousness). Each of the dimensions has six lower-order facets.
The team found that BD II patients had significantly higher NEO-PI-R scores than BD I patients on the neuroticism dimension (110.7 vs 97.8) and four of its lower-order facets, namely anxiety (20.2 vs 17.3), depression (19.9 vs 16.1), self-consciousness (19.4 vs 17.2), and vulnerability (22.2 vs 15.6).
Conversely, patients with BD II had significant lower scores than BD I patients on the extraversion dimension (95.3 vs 107.5) and its lower-order positive emotion facet (17.4 vs 18.3).
In addition, although there were no significance differences between the groups regarding scores on the conscientiousness dimension, BD II patients had significantly lower scores than BD I patients for the lower-order facets of competence (16.1 vs 18.6) and achievement striving (17.2 vs 19.3).
There were no significant differences between the groups regarding openness and agreeableness dimension scores.
Joo et al conclude: "Our results clearly suggest that BD I and BD II patients have distinct personality which supports the separation in enduring trait dimensions between the two subtypes.
"The most evident differences were on measures of neuroticism and extraversion."
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