Fourth, previous studies have suggested that changes in BDNF levels differ at different stages after stroke (Di Lazzaro et al., 2007; Jimenez et al., 2009; Chan et al., 2015; Zhang et al., 2017), and although we controlled the analysis for time from symptom recognition to admission and time from enrolment to onset, we may still have missed the observation time window for BDNF changes in some patients. This evidence concerns the gene BDNF and Stroke.