Why does weed make me panic attack level anxious when everyone else gets so relaxed?

I've smoked everything from schwag to medicinal. For example my buddy left some decent nug here and I decide to smoke, and I honestly went into panic attack mode and had to go for a walk because I thought I was going to freak out. Is there a scientific reason? Is it my brain chemistry?

Tl;dr why does pot make me anxious as f when everyone else gets chill?