So, we should expect that people with depression would have low levels of 5-HIAA meaning they have low serotonin.

因此，如果抑郁症患者的 5-HIAA 水平低，那么他/她的 5-羟色胺水平肯定也低。

Then, in 1975, investigators at the Karolinska Institute in Stockholm found that thirty percent of the depressed patients they tested indeed suffered from low levels of the serotonin metabolite 5-HIAA.

1975 年，斯德哥尔摩卡罗林斯卡学院的研究人员发现，在他们测试过的抑郁患者中有 30% 的人的 5-HIAA（5-羟色胺代谢物）水平偏低。

After serotonin is pumped into the synapse, it is either taken up into the pre-synaptic neuron for later use or it is metabolized by an enzyme into 5-hydroxyindole acetic acid (5-HIAA).

5-羟色胺被“泵”入神经突触后，要么被带到前突触神经元备用，要么被某种酶代谢成 5-羟基吲哚乙酸（5-HIAA）。

In 1971, investigators at McGill University failed to find a " statistically significant" difference between the 5-HIAA levels of depressed patients and normal controls; and there was no correlation whatsoever between depression severity and levels of 5-HIAA.

1971 年，麦吉尔大学的研究人员发现，抑郁患者和对照组受试者的 5-HIAA 水平没有任何区别；而且，抑郁程度和 5-HIAA 水平高低也没有任何关系。