It is thought that BDNF promoter methylation, BDNF/TrkB levels, BDNF-AS (BDNF antisense RNA), and TrkB isoforms can be used as biomarkers for early diagnosis and risk determination in neurodegenerative diseases where the deficiency of BDNF and TrkB signaling is thought to play a role. The gene discussed is BDNF; the disease is neurodegenerative disease.