There has been at least one: https://www.mdpi.com/2077-0383/13/1/227 https://www.mdpi.com/2077-0383/13/1/227 The references section has some interesting studie

There has been at least one: https://www.mdpi.com/2077-0383/13/1/227 https://www.mdpi.com/2077-0383/13/1/227 The references section has some interesting studies about what specific mechanisms might allow for that, and the conclusion appears to be immune/inflammatory regulation by the ECS.