It was also found that lower levels of brain-derived serum neurotrophic factor (BDNF) occurred in patients with panic disorders, further suggesting that BDNF may contribute to the therapeutic response in panic disorders [75], which was confirmed by research by Suliman et al., who confirmed significantly lower levels of brain-derived neurotrophic factor (BDNF) in the plasma of people suffering from GAD compared to the control group. This evidence concerns the gene BDNF and generalized anxiety disorder.