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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