INTJ, on the borderline with INTP. And when I'm doing well, the introversion is pretty mild as well, I like to party and whatnot but do need alone time to recharge. When I am down I get much more introverted.

It's interesting to see the INTJs (~1% of the population) and the NT types in general be so overrepresented here. I get the feeling that something about being an NT type or maybe an N type in general may be associated to some degree with mental illness - in part, I suspect, due to society being poorly adapted to us.

My favorite people to hang with are probably *NFPs though. As an INTJ I'm definitely an engineering type but I have enough F and P that I really relate well with *NFPs and admire their free spirit. My favorite online friend is an INFP and we have almost the same brain, same specific flavor of bipolar, can instantly understand each other's nuanced description of moods etc, but I am an engineer and she is a mystic