Yeah it was most definitely the change in strain that caused it. Indica causes a "body high" while Sativa causes a "mind high". Being a heavy cannabis user myself, there was one point where I had the same types of things happening after smoking chronic ($20 a gram, most the time sativa based). I would be walking and feel like my knees snapped and actually expected to tumble to the ground, thinking my face skin just slipped off my head, thinking my lung collapsed/ heart exploded, you name it. Along with extreme paranoia and constant panic attacks.

I had almost given up smoking weed all together but I kept smoking. What I realized is your mind has everything to do with it. I can now smoke as much weed I can get my hands on and not even worry about the same things. Just realize that you won't ever die from it and if you start trippin out (and it feels bad) just either forget about it and it will go away or change it. It really has a lot to do with the mental state of the patient. If their not able to keep controle then their likely to get scared.