However, the LPS raise detected in patients with a-MDD could also cause the TLR-4 expression increment: r-MDD patients have been a-MDD formerly, and thus, the higher LPS levels during their a-MDD period could be activating the TLR-4, causing the TLR-4 increment detected in their r-MDD phase. This evidence concerns the gene TLR4 and major depressive disorder.