BDNF and major depressive disorder: The finding of decreased levels of BDNF in patients with more severe depressive symptomatology confirmed with the multiple linear regression (β = −4.73, t = −2.4) are concordant with the results of a recent study where the reduction of the BDNF levels was correlated to the dimensional function of the depression and was not related to positive, negative, or to other general symptoms of SCZ and SAD [48].