Notes:
The VNTR is a functional variant: Alleles with 4 copies may lead to higher MAOA expression and relatively lower dopamine levels than 3-copy alleles (Chen et al., 2004; Sabol et al., 1998).
The cited study (Treister et al., 2009) shows no association of variants with cold pain threshold, or cold or heat pain intensity.
Negative results: Treister et al., 2011 report no association of MAOA and conditioned pain modulation.
Ishii et al., 2011 report no association of the VNTR with migraine in a small study of 91 migraineurs and 191 healthy controls.
