If this theory is applied on our results and we compare the 5-HT4R levels at rΔHAMD6 equal to 0% (i.e., the results from the third layer of the LVM), we compare the effect of OC use with a population with a non-serotonergic subtype of MDD, which reveals an OC effect equal to about -20%. This evidence concerns the gene HTR4 and major depressive disorder.