GDNF and major depressive disorder: Taking into account the potential involvement of GDNF in controlling neuronal networks of epileptic brain [17], the aim of this study was to assess GDNF levels in LF and BS as well as to evaluate HPA and inflammatory indices in patients with focal epilepsy (FE) and in patients with epilepsy and comorbid depression (FE + MDD) compared with patients with depression (MDD) and healthy controls (HC).