In both the abstract and "Comment" section of their recent report, Higley et al1 state that plasma cortisol concentrations and "stress hormones" (plural emphasized) were positively correlated with a measurement of aggression. It is not clear what this is based on, since the correlation between plasma cortisol and aggression ratings in Table 2 of their article is essentially zero. If this is not a typographical error, it puts into question the authors' claim of a relationship between increased stress, serotonin, and aggression in their animal population, as does the absence of significant intercorrelations between 5-hydroxyindoleacetic acid (5-HIAA) levels in the cerebrospinal fluid (CSF) and the other stress measures identified, ie, CSF norepinephrine and plasma corticotropin.
Although it is in support of other work, the conclusion that the findings indicate that excessive aggression is related to diminished CSF 5-HIAA concentrations in nonhuman primates also seems overstated, in view of the
Reus VI. Are Stress Hormones and Serotonin Related to Aggression in Primates?. Arch Gen Psychiatry. 1994;51(1):72-73. doi:10.1001/archpsyc.1994.03950010072011