Huang et al. [30] also found a strong linkage disequilibrium between these MAOA variants but found no significant differences in the haplotype frequencies in total MDD patients (DSM-IV major depression; HAM-D ≥ 18) or MDD clinical subgroups (18 ≤ HAM-D ≤ 24: moderate MDD; HAM-D > 24: severe MDD; MDD with and without a first-degree family member with a history of MDD or bipolar disorder) versus controls (p > 0.05, data not shown). This evidence concerns the gene MAOA and major depressive disorder.