BDNF and major depressive disorder: The secondary outcomes, in addition to those presented in this work, included monitoring of the omega-6/omega-3 FAs ratio [24], lipid parameters [25] and indirect markers of inflammation, such as thromboxane B, homocysteine or brain-derived neurotrophic factor (BDNF) and vitamin D [26] in relation to depression severity and the possible effect of omega-3 FA intervention.