Kanna is an ssri, and ssri's don't work the same for everyone. They basically only work if you don't have enough serotonine on your own. I have been on prozac for a year and in the last few months I didn't feel anything but the side effects. Then I just quit. However in the first weeks/months when I took it it really helped, during the first two weeks it almost felt like mdma when I had alcohol with it.
When I'm using Kanna for a few days in a row then the effects are totally gone. The first day it feels relaxing and nice, but that's it. Smoked with weed it works somewhat better. However I won't buy kanna again, it's not worth the snorting pain.