MAOA and major depressive disorder: Human studies linking the MAOA-uVNTR to affective disorders are rare, but a study in healthy female Korean nursing students found a non-significant increase in Beck's Depression Inventory scores when comparing 4/4 repeats (high activity), 3/4 repeats (classified as low activity in this study) and 3/3 repeats (low activity) (Yang et al., 2007).