(Exploring Your Mind) Rage and depression are both expressions of frustration, discomfort, and unease in the face of reality. They represent a failed processing of internal malaise. Someone who’s always mad is probably depressed and vice versa.
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Molecular Imaging Finds Link Between Low Dopamine Levels and Aggression
(Eurekalert) Study shows people who have lower levels of the brain chemical are more likely to be aggressive when provoked in competitive situations