Risk-taking behavior in bipolar disorder (BD) is not characterized by a generalized tendency to risk-taking, but involves reduced sensitivity to psychologic factors that promote and inhibit risky behavior related to value outcomes, suggest study results.

Previous studies showing evidence of impairments on neuropsychologic tests of decision-making in BD have involved patients with lengthy periods of illness, comorbid disorders, and who have been taking medication over prolonged periods of time.

“Consequently, decision-making impairments in such samples might reflect the consequences of, and adaptations to, previous episodes of bipolar illness rather than the operation of underlying causal mechanisms,” write Robert Rogers (University of Oxford, UK) and co-authors in the journal Biological Psychiatry.

The researchers recruited 20 euthymic, medication-free participants aged 19 years on average with previously undiagnosed BD type II or BD not otherwise specified and 20 age-and IQ-matched healthy individuals from a student population using an online survey that included the Mood Disorders Questionnaire.

Participants were asked to complete a computerized risky decision-making task consisting of a series of dilemmas involving gambles to gain rewards (positively framed) or to avoid suffering losses (negatively framed).

The proportion of risky choices made by both groups was identical, and all participants chose the risky option significantly more often in response to negatively- compared with positively-framed dilemmas. However, the difference in the distribution of risk choices between positively- and negatively-framed dilemmas in individuals with BD was significantly lower compared with controls (0.17 vs 0.32).

BD participants were significantly slower to select the safe options in the positively-framed dilemma compared with controls. No between-group differences were seen for negatively-framed dilemmas.

“Accordingly, we propose that the psychometric functions relating gains and losses to their subjective values are steeper in individuals with BD,” say Rogers and team.

The study also showed that individuals with BD significantly overestimated the number of bad outcomes arising from positively-framed dilemmas compared with controls (3.37 vs 2.40), “suggesting that opportunities to secure gains through risk-averse behavior are appraised negatively in BD,” say the authors.

“Thus, BD might generate turbulent reinforcement histories with an increased proportion of negative events that might engender anxiety or destabilize mood in affected individuals,” concludes the team.

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

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Bipolar disorder and major depressive disorder (MDD) patients have differences in amygdala and orbitomedial prefrontal cortex (OMPFC) effective connectivity (EC) in response to happy faces, say researchers.

Bipolar depression is the most common presentation of bipolar disorder and often leads to a misdiagnosis of MDD. However, as emotional dysregulation is a central feature of bipolar disorder, neural dysfunction in systems supporting emotional regulation may help to discriminate the two groups.

To investigate further, Mary Phillips, from the University of Pittsburgh in Pennsylvania, USA, and colleagues studied 15 bipolar depressed and 16 MDD patients matched for age, age of illness onset, illness duration, and depression severity, and 16 age- and gender-matched healthy controls.

The participants were administered two event-related paradigms labeling the emotional intensity of happy and sad faces, respectively, during which OMPFC and amygdala blood oxygen level dependent signals were measured. Dynamic causal modeling was then used to examine significant among-group alterations in EC between right- and left-sided neural regions.

There were no differences among the groups in the labeling of emotional faces in either experiment, with no significant differences between the two depressed groups, the team notes in the journal Biological Psychiatry.

Compared with controls, both bipolar disorder and MDD patients had significantly reduced left-sided top-down OMPFC-amygdala EC during the happy experiment. EC values were positive for controls, close to zero for bipolar disorder patients, and negative for MDD patients.

Whereas bipolar disorder patients had significantly reduced right-sided bottom-up OMPFC-amygdala EC in response to the happy experiment, there were no significant differences between MDD patients and controls. EC values were positive for controls and MDD patients but negative for bipolar disorder patients.

The results also showed that, compared with controls, both MDD and bipolar disorder patients had significantly reduced left-sided top-down OMPFC-amygdala EC during the sad experiment.

“We show that bipolar depression and major depression are associated with different patterns of abnormal functional integration between different regions in neural systems supporting emotion regulation, in both hemispheres during happy emotion processing,” the team writes.

“This finding in turn suggests that different pathophysiological mechanisms might underlie these two types of depression and is a promising step forward toward identifying biological markers to distinguish between these different illnesses.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

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Individuals at high risk for hypomania have alterations in sleep and circadian activity similar to those seen in bipolar disorder patients, indicating that such phenomena are not simply an artefact of the illness, conclude UK researchers.

It is common for bipolar disorder patients to experience sleep and circadian rhythm disturbances, which are associated with illness severity and recurrence. However, the premorbid occurrence and significance of such disturbances is not known.

Steven Jones (Lancaster University) and Dave Ankers (South Staffordshire and Shropshire Healthcare NHS Foundation Trust) studied 31 individuals at behavioral risk for hypomania, as measured on the Hypomanic Personality Scale (HPS), and 24 age- and gender-matched healthy controls.

The participants wore an actigraph for 7 days to obtain sleep and circadian activity data, and completed the HPS, the Hypomanic Interpretations Questionnaire (HIQ), the Internal State Scale (ISS), and a sleep diary.

At-risk individuals scored significantly higher than controls on the HIQ, with the results indicating that not only did at-risk participants make more positive self-referent appraisals for hypomania-relevant experiences than controls, but alsohad more of those experiences.

The team also found that at-risk individuals had a significantly reduced relative amplitude of activity cycle than controls, at 0.81 versus 0.86, suggesting that there was a smaller difference between the most active and least active periods in a day.

Hypomania-risk participants had a significantly shorter sleep duration than controls, at 6:53 versus 7:28 h:m, as well as significantly more variable sleep duration, fragmentation of sleep, and sleep efficiency. They also reported significantly later bedtimes than controls, at 1:20 versus 0:16 h:m.

The team writes in the Journal of Clinical Psychology: “This study found some evidence that circadian markers do differ in those putatively at risk for bipolar disorder when compared with controls.

“This may indicate that circadian differences exist prior to illness onset and could, therefore, represent a core vulnerability for the disorder.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

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