““drugs that decrease “serotonergic tone” (i.e., decreasing serotonin levels or sensitivity to serotonin) increase impulsive aggression; raising the tone does the opposite. This generates some simple predictions—all of the following should be associated with impulsive aggression, as they will produce low serotonin signaling: a. Low-activity variants of the gene for tryptophan hydroxylase (TH), which makes serotonin b. High-activity variants of the gene for monoamine oxidase-A (MAO-A), which degrades serotonin c. High-activity variants of the gene for the serotonin transporter (5HTT), which removes serotonin from the synapse d. Variants of genes for serotonin receptors that are less sensitive to serotonin””
