I remember finding some student's study on MBTI and brain differences a while back online. It wasn't that conclusive due to the sample size, but interesting nonetheless. I think that there are definitely physical symptoms( brain scans) that can show type to be a pretty stable trait. Theres a whole host of variables that can influence that though. I think it would be really cool if someone would invest enough time to do a more wide scale study on that.
My cold, snide, intellectual life is just a veneer, behind which lies the plywood of loneliness.