19 yrs, female. depression and anxiety. once so stressed, the vessel inside the left neck constricted for a very quick sec. what happened?

Are you sure it was?: Are you sure it was a blood vessel? It would make more sense for it to be a muscle, like the platysma. This is a muscle under our chin, it attaches to the collarbone. It could contract briefly. Some people can make it contract for amusement. No matter what it was, this will probably be ok. Can't think of anything bad that does this.