This randomized, double-blind, placebo-controlled, crossover study was published in the journal Sleep in June 2021. Twenty-three participants were tracked over a period of two weeks.
They used an extract containing THC, CBN, and CBD called ZTL-101. Patients were given a single dose (THC/CBN/CBD; 10/1/0.5 mg), and in some participants, a double dose (THC/CBN/CBD; 20/2/1 mg). ZTL-101 contains THC 20 mg/mL, CBN 2 mg/mL, CBD 1 mg/mL and naturally occurring terpenes, extracted from the cannabis plant, in pharmaceutical grade sunflower oil as the diluent.
"Two weeks of nightly sublingual administration of a cannabinoid extract (ZTL-101) is well tolerated and improves insomnia symptoms and sleep quality in individuals with chronic insomnia symptoms."
The full paper is here.