I was diagnosed Schizoid Personality in 1992. That pretty well ran off the therapists stating they could not help me. I find this is one I just have to live with as no treatment is useful.
I add that I am Schizoid in a way that I am the gauge by which others fall short. 61 years old and no relationships, not even family. And no friends of any closeness since I was in the Army in the late 60's.