Psychologic model highlights bipolar subtypes
medwireNews: Studying the Behavioral Activation System (BAS) in patients with bipolar disorder reveals important differences between the bipolar I and II disorder subtypes, say researchers.
"Treatments for bipolar II disorder are commonly simply extrapolated from research based on bipolar I disorder samples, yet identification of differentiating features in the bipolar sub-types argue the need for tailored interventions," say lead researcher Kathryn Fletcher (University of New South Wales, Sydney, Australia) and team.
Overall, they found that scores on the Behavioral Inhibition System/BAS measure were higher in 69 patients with bipolar I disorder than in 82 with bipolar II disorder, after controlling for age and baseline symptoms.
This is in line with the theory that bipolar I disorder patients have higher BAS sensitivity than bipolar II patients, says the team, with extreme reactivity to reward manifesting as mania.
Over 6 months of follow up, BAS scores in both groups were associated not with symptom severity but with variability. This is consistent with changes in mood over time averaging out at no correlation, say the researchers, whereas BAS scores accurately reflect patients' mood variability arising "from excessive reactivity to both negative and positive occurrences in life."
Analysis of BAS subscales revealed key differences between the two groups of patients, however, with the Drive and the Reward Responsiveness subscales significantly associated with mania in patients with bipolar I but not II disorder. By contrast, scores on the Fun Seeking subscale correlated with mania/hypomania in both groups.
Fletcher et al say that Drive reflects people's motivation to obtain or achieve something. "The tendency for those with bipolar disorder to excessively focus on and engage with reward-focused situations may arise from their tendency to place overly high value on goals of an ambitious, self-focused nature," they comment in the Journal of Affective Disorders. The current findings suggest this to be of particular relevance to mania in patients with bipolar I disorder, they add.
High BAS Drive scores were also significantly associated with depression in bipolar II disorder, contrary to the researchers' hypothesis that low BAS sensitivity would be linked to depression. The team suggests that bipolar II disorder patients tend to underestimate the potential for failure, and this, combined with high BAS Drive, leads them into unexpected failures, triggering depressive mood episodes.
The findings show that BAS has an important but somewhat different role in patients with bipolar I and bipolar II disorder, conclude Fletcher et al. "These aspects may benefit from a specific focus in psychological interventions."
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Eleanor McDermid, Senior medwireNews Reporter