BDNF and generalized anxiety disorder: The aim of the present research was to explore whether BDNF may represent a biomarker of ADs by comparing serum BDNF levels among adult patients with different subtypes of ADs which were Generalized Anxiety Disorder (GAD), Specific Phobia (PHSP), Panic Attack Disorder (PAD), Social Phobia (PHSOC) and healthy donors, in a large population sample (n = 672 subjects).