I think personality disorders are fairly difficult to diagnose. A psychiatrist friend told me that he sees people regularly with "Borderline Personality Disorders but that a major personality disorder diagnosis is always approached carefully as the implications for the patient might be severe.
I suspect from what I have read of Jeremy in his younger years that he may well have had a personality disorder of some kind. I also look at Sheila and her issues as well......neither of them had an easy start in life.
You can have a personality disorder but it doesn't make you a killer, generally though people with certain types of personality disorder will have problems empathizing with others. As a worker with parents who had personality disorder issues I found the ability to parent could be very affected in a negative way:(
Which in turn leads me to wonder about June and her mental health issues. This is not a criticism of June in any way, just an observation that she obviously found life challenging at times....as we all do. Did she have some kind of personality disorder Did this negatively affect both Sheila and Jeremy?