GDNF and major depressive disorder: According to the selected model, reducing the GDNF level in LF by one unit increases the probability of developing MDD by 2%, increasing the cortisol level in BS by one unit elevates the probability of developing MDD by 1%, and increasing the TNF-α level by one unit elevates the probability of developing MDD by 80% (Change in Odds%: (OR-1)*100).