Real-life decisions are often complex because they involve making sequential choices that constrain future options. We have previously shown that to render such multi-step decisions manageable, people ‘prune’ (i.e. selectively disregard) branches of decision trees that contain negative outcomes. We have theorized that sub-optimal pruning contributes to depression by promoting an oversampling of branches that result in unsavoury outcomes, which results in a negatively-biased valuation of the world. However, no study has tested this theory in depressed individuals.

Thirty unmedicated depressed and 31 healthy participants were administered a sequential reinforcement-based decision-making task to determine pruning behaviours, and completed measures of depression and anxiety. Computational, Bayesian and frequentist analyses examined group differences in task performance and relationships between pruning and depressive symptoms.

Consistent with prior findings, participants robustly pruned branches of decision trees that began with large losses, regardless of the potential utility of those branches. However, there was no group difference in pruning behaviours. Further, there was no relationship between pruning and levels of depression/anxiety.

We found no evidence that sub-optimal pruning is evident in depression. Future research could determine whether maladaptive pruning behaviours are observable in specific sub-groups of depressed patients (e.g. in treatment-resistant individuals), or whether misuse of other heuristics may contribute to depression.

现实生活中的决策通常很复杂，因为它们涉及做出限制未来选择的连续选择。我们之前已经表明，为了使此类多步骤决策易于管理，人们会“修剪”（即有选择地忽略）包含负面结果的决策树分支。我们的理论是，次优修剪通过促进分支的过度采样而导致抑郁，从而导致令人不满意的结果，从而导致对世界的负面评估。然而，还没有研究在抑郁症患者中测试过这一理论。

30 名未接受药物治疗的抑郁症参与者和 31 名健康参与者接受了连续的基于强化的决策任务，以确定修剪行为，并完成了抑郁和焦虑的测量。计算、贝叶斯和频率分析检查了任务表现的群体差异以及修剪和抑郁症状之间的关系。

与之前的发现一致，参与者对开始时损失较大的决策树分支进行了大力修剪，无论这些分支的潜在效用如何。然而，修剪行为没有群体差异。此外，修剪与抑郁/焦虑水平之间没有关系。

我们没有发现任何证据表明抑郁症中明显存在次优修剪。未来的研究可以确定在抑郁症患者的特定亚群（例如对治疗有抵抗力的个体）中是否可以观察到适应不良的修剪行为，或者滥用其他启发法是否可能导致抑郁症。