Sex similarities and differences in the neurobiology of aggression

Functional MRI studies demonstrated that conduct disorder (CD) is associated with abnormal brain function and connectivity, and impaired neuroendocrine responsivity in adolescents (boys and girls). The observed sex-specific effects of CD on responses in some brain regions and structural connectivity in some tracts may partly explain sex differences in the presentation and course of CD [1].

Dr Graeme Fairchild (University of Bath, UK) and colleagues conducted functional and structural MRI experiments to study neural responses during emotional and neutral face processing and structural connectivity, using Tract-Based Spatial Statistics in adolescents with CD and sex-matched typically developing (TD) controls. Also measured were cortisol, oxytocin, and testosterone responses to a standardised psychological stress induction procedure (the Trier social stress test). Participants were divided into 4 groups: CD boys, CD girls, TD boys, and TD girls.

Neuroimaging findings showed common effects of CD in boys and girls, including common increases in striatal activity to emotional faces and altered corpus callosum connectivity. Sex differences were found in certain imaging measures, such as CD-related effects on amygdala responses to angry faces, which were highest in CD boys and lowest in CD girls.

Neuroendocrine stress reactivity demonstrated that boys and girls with CD had blunted cortisol, testosterone, and oxytocin responses to psychological stress, albeit at different time scales: cortisol and testosterone response was slower, that of oxytocin much faster. This was the case despite strong increases in feelings of stress and anxiety in all 4 groups, suggesting a reduced coordination between physiological and psychological stress response systems in CD.

One of the mechanisms that could explain this blunted hormonal stress response in CD individuals, could be allostatic load, Dr Fairchild suggested. “These kids have been under much more stress throughout their lives, had high levels of adversity and maltreatment; therefore their hypothalamic–pituitary–adrenal axis and other neuroendocrine systems simply do not function as well or need much higher levels of stress to show a hormonal influx.”

1. Fairchild G. Sex similarities and differences in the neurobiology of aggression: evidence from structural and functional neuroimaging and stress neuroendocrinology. S.01.01, ECNP 2021 Congress, 2–5 October.

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Posted on 26 November, 2021