BDNF and insomnia: Studies show that abnormal serum 5-HT levels in patients with IS and insomnia are significantly related to decreased sleep quality.[38] Serum NGF is an important factor to promote nerve cell growth and nerve repair, and its level expression can directly reflect the recovery of nerve function.[39] BDNF stands as a pivotal member within the neurotrophic factor family, predominantly residing in the hippocampus and cortex regions.