Plant extracts for sleep disturbances: A systematic review 

This 2020 review provided insight into a number of botanical herbs that have been used for sleep support. Relating to valerian, the review found 17 relevant studies to review. The results showed variability in impact however several of the studies did show improvements in sleep quality with doses from 160-600 mg/day. Five studies demonstrated improved sleep latency and duration, and amelioration of insomnia severity.  

References:

Guadagna S, Barattini DF, Rosu S, Ferini-Strambi L. Plant Extracts for Sleep Disturbances: A Systematic Review. Evid Based Complement Alternat Med. 2020;2020:3792390. Published 2020 Apr 21. doi:10.1155/2020/3792390