The Minor "G" allele is associated with:
- People who produce more MAO-A protein (G or GG) aren't as affected by the placebo effect (R).
- Increased outward anger in females and aggression in males.
Monoamine oxidase A degrades serotonin, dopamine, epinephrine, and norepinephrine. The G allele encodes for the higher activity form of the enzyme. Subjects with major depressive disorder with the highest activity form of the enzyme (G or G/G) had a significantly lower magnitude of placebo response.