Background: Patients with major depressive disorder (MDD) show suboptimal decision-making strategy in experimental game situations. The influence of personality traits and genetic variations on decision-making is not known.
Methods: Contingency learning based on the cumulative effect of reward and punishment was assessed in 124 patients with unipolar MDD using the ABCD (reward sensitivity) and EFGH (punishment sensitivity) versions of the Iowa Gambling Test. All patients were genotyped for serotonin transporter promoter polymorphism (5-HTTLPR) and received the Temperament and Character Inventory (TCI).
Results: Patients with the ll genotype achieved higher persistence scores and used more optimal decision-making strategy on the ABCD task compared with patients with the ss genotype. Higher persistence was associated with better performance on the ABCD task, and higher harm-avoidance was associated with worse performance on the EFGH task.
Limitations: Healthy control volunteers were not included. Personality traits and decision-making were not assessed with multiple questionnaires and tasks. Type I errors cannot be excluded.
Conclusions: Decision-making strategy is influenced by personality traits and genetic variations in patients with MDD. Patients carrying the ss variant of the 5-HTTLPR show less persistence and tend to be influenced by high immediate reward.