For example, DNA methylation as well as histone acetylation represent key factors in regulating the BDNF gene, which encodes brain-derived neurotrophic factor (BDNF), a protein that is involved in numerous neurological conditions such as schizophrenia, depression, epilepsy, Alzheimer’s disease, obesity and drug addiction at many stages of development [40]. The gene discussed is BDNF; the disease is depressive symptom measurement.