MedWire News: Researchers have found that patients with bipolar disorder (BD) show equally poor decision-making ability across all three phases of the illness compared with mentally healthy individuals.
Writing in the journal Biological Psychiatry, Marc Adida (Mediterranean University, Marseille, France) and team explain: "Although trait-related cognitive impairments have been reported in BD patients, the nature and extent of decision-making dysfunction across the phases of the illness remain unclear."
To investigate, the team studied 167 BD patients, aged between 18 and 65 years, and 150 age-, IQ-, and gender-matched mentally healthy individuals (controls). Of the BD patients, 45 were manic, 32 were depressed, and 90 were euthymic at the time of the study.
All of the participants were assessed for decision-making ability using the Iowa Gambling Task (IGT). For this task, each participant is required to make a series of 100 choices from four decks of cards, labelled A, B, C, and D for a pretend monetary reward.
Decks A and B are associated with high immediate wins, but occasional large penalties that result in a net loss over time. Decks C and D are associated with smaller immediate wins, but lower long-term losses, such that participants accumulate gradual profit from choosing these decks.
Decks B and D provide low-frequency but high-magnitude penalties, whereas decks A and C provide high-frequency but low-magnitude penalties.
Thus, decks C and D are classified as "safe" whereas decks A and B are classified as "risky".
The researchers found that the BD patients selected significantly more cards from the risky decks than controls did, with no significant differences among the manic, depressed, and euthymic groups.
However, when IGT performance was analyzed according to sensitivity to punishment frequency, all four groups preferred decks offering low-frequency penalties (B and D) over those with high-frequency penalties (A and C), with no significant differences among the four groups.
Multivariate analysis revealed that decision-making impairments were predicted by low levels of education, increased levels of depression, a family history of BD, and nonuse of serotonin and norepinephrine reuptake inhibitor antidepressants.
Adida and team conclude: "Bipolar disorder patients have a trait-related impairment in decision-making that does not vary across illness phase."
They add: "The observation that trait-related deficits in BD are characterized by an objective failure to weigh costs versus benefit in a simple game is of clinical interest and may represent a future therapeutic target."
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