This study tracked 991 users of the Strainprint app (for 3 years) who had identified insomnia as a condition they were treating with cannabis products. It was published in the Journal of Medical Internet Research in October 2021.
Overall, the users felt that the cannabinoid products were effective across all genders and ages with no significant differences among different product forms or ingestion methods. It did show that THC-dominant cultivars were perceived to be more effective than CBD-dominant cultivars, and that "indica" cultivars were better than "sativa" cultivars. The vast majority of sessions were reported as using flower or oil (concentrate).
"Although all strain categories were perceived as efficacious, predominant indica strains were found to reduce insomnia symptomology more than cannabidiol (CBD) strains and predominant sativa strains. Indica hybrid strains also presented a greater reduction in insomnia symptomology than CBD strains."
The full paper is here at the Journal of Medical Internet Research site.