Department of Psychiatry, University of Cambridge, Cambridge, UK.
J Psychopharmacol. 2010 Apr;24(4):573-83. doi: 10.1177/0269881108100257. Epub 2009 Jan 22.
Reduction of the monoamine serotonin (5-HT) via the dietary manipulation of tryptophan (acute tryptophan depletion; ATD) has been shown to induce negative cognitive biases similar to those found in depression in healthy individuals. However, evidence also indicates that there can be positive effects of ATD on both mood and reinforcement processing. Here, we present two separate studies, with remarkably similar findings, which may help explain these discrepancies. In both experiments, we assessed cognitive biases following experimentally induced mood states under both a balanced amino acid drink (BAL) and ATD. A significant interaction between treatment, mood state and cognitive bias was observed in both experiments. In the first experiment, subjects undergoing positive mood induction demonstrated a positive cognitive bias on BAL, which was abolished by ATD. The same effect was observed in subjects undergoing neutral mood induction in the second experiment. These effects replicate findings in healthy individuals undergoing ATD. Subjects undergoing negative mood induction, by contrast, demonstrated the opposite pattern of results; in both experiments, they showed no bias under BAL but induction of a positive cognitive bias by ATD. These results mimic previous findings in currently depressed patients undergoing ATD. We therefore suggest that mood state moderates the effect of ATD on cognitive biases. This, in turn, has important implications for the understanding of the role of 5-HT in psychiatric disorders.
通过饮食控制色氨酸（急性色氨酸耗竭；ATD）来减少单胺类神经递质 5-羟色胺（serotonin；5-HT），已被证明会在健康个体中诱导出类似于抑郁的负面认知偏差。然而，有证据表明，ATD 对情绪和强化处理也可能有积极影响。在这里，我们呈现了两项具有相似发现的独立研究，这可能有助于解释这些差异。在这两项实验中，我们在平衡氨基酸饮料（BAL）和 ATD 两种条件下，评估了实验诱导的情绪状态后的认知偏差。在这两项实验中，都观察到了治疗、情绪状态和认知偏差之间的显著交互作用。在第一项实验中，经历积极情绪诱导的受试者在 BAL 条件下表现出积极的认知偏差，而 ATD 则消除了这种偏差。在第二项实验中，经历中性情绪诱导的受试者也出现了同样的效果。这些结果复制了在经历 ATD 的健康个体中观察到的结果。相比之下，经历消极情绪诱导的受试者则表现出相反的结果模式；在这两项实验中，他们在 BAL 条件下没有表现出任何偏差，但 ATD 诱导出了积极的认知偏差。这些结果与正在经历 ATD 的当前抑郁患者的先前发现相似。因此，我们认为情绪状态调节了 ATD 对认知偏差的影响。这反过来又对理解 5-HT 在精神障碍中的作用具有重要意义。
