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。