In most of the studies, lower doses of CBD (10 milligrams per kilogram, mg/kg, or less) improved some symptoms of anxiety, but higher doses (100 mg/kg or more) had almost no effect.

The way that CBD acts in the brain can explain why this happens https://ventsmagazine.com/2021/10/06/why-you-need-to-know-about-the-origin-of-cbd-cream/. In low doses, CBD may act the same as surrounding molecules that normally bind to the receptor, which "turns up" their signaling.