This randomized, parallel-group, double-blind, placebo-controlled trial study examined the anti-anxiety (anxiolytic) effects of a single 300mg dose of CBD isolate administered orally in capsules to patients before a PTSD triggering event. It was published in the Brazilian Journal of Psychiatry in March 2022.
It was a simple study, but makes some meaningful conclusions. The reduction in anxiety was significant vs. placebo (sugar pill) in patients when dealing with nonsexual trauma. There was no significant reduction with patients dealing with sexual trauma.
"A single dose of CBD (300mg) attenuated the increased anxiety and cognitive impairment induced by recalling a traumatic event in patients with PTSD when the event involved nonsexual trauma."
The full-text study is available here at Scielo Brazil.