The common belief that testosterone causes aggression is incorrect. Testosterone is converted into estrogen in the brain via an enzyme called aromatase. It is this brain-derived estrogen binding to specific receptors that directly activates the neural circuits for aggression in both males and females.
The impact of estrogen on aggression is context-dependent. During long days with ample sunlight, estrogen does not evoke aggression. However, during short days, which are associated with higher stress hormones and lower dopamine, increased estrogen levels heighten the predisposition for aggressive behavior.
The pop psychology notion that "aggression is just amplified sadness" is biologically false. Neuroscience shows that the neural circuits in the brain responsible for aggression are completely separate from those that govern grief and mourning. While you can feel both simultaneously, one is not a manifestation of the other.
Aggression is not a switch that flips but a sequence of neural circuit activations with a beginning, middle, and end. Understanding it as a verb or a process allows for intervention at various stages—preventing its initiation, halting it mid-course, or even prolonging it if adaptively necessary.
Conrad Lorenz's model of aggression as a "hydraulic pressure" accurately reflects its biological underpinnings. Hormones, neurotransmitters, stress levels, and external stimuli all converge to increase or decrease this internal pressure, biasing an individual toward or away from an aggressive outburst. This pressure build-up is often observable.
High levels of the stress hormone cortisol, combined with low levels of serotonin, increase the "hydraulic pressure" for aggression. This state primes the sympathetic nervous system for reactivity. Managing cortisol through tools like sunlight exposure, sauna, or ashwagandha can directly reduce the biological tendency toward aggression.
A randomized, double-blind, placebo-controlled study found that supplementing with acetyl L-carnitine significantly reduced aggressive behavior, delinquency, and attentional problems in children with ADHD. This points to a potential nutritional tool for managing impulsivity and aggression.