BDNF and heart failure: In the study by Halloway et al. (2020), which included 35 studies (1 controlled intervention, 1 before–after study with no control group, 13 case–control studies, 20 observational cohort and cross-sectional studies), the authors demonstrated that (1) patients with heart failure had lower BDNF levels compared with control subjects, and (2) patients with unstable angina and myocardial infarction had higher BDNF levels.