What evidence is there that Sheila had ever been cruel to her children? Neglected them to some extent possibly, but committed abject cruelty? I just don't buy the 'mother in distress' thing.
Bridget,please read up about these women who are mentally unstable and what they are capable of doing.
They are wild,believe you me. I've seen it,,I've worked with them. Read about the use of paraldehyde on violent patients.
Sheila did have a tendency to be violent. The night of the murders was an example when she killed her children. If she couldn't continue to look after them,,nobody else was going to do.
Probably if that night of carnage hadn't have occurred,,then it's quite possible that she,herself would at some point have committed suicide. It's known amongst schizophrenics,,and their lives in any case,are usually short-lived.
Hormonal imbalance has got a lot to answer for,,as in an over-active thyroid which in itself causes anxiety and if not treated can cause a lot of problems. This too is something that can be brought on by pregnancy, but symptoms can be sketchy,but a blood test can define this,then treatment can begin.
My belief is that Dr Ferguson neither knew enough,nor did enough to curtail Sheila's illness.
Rather an endocrinologist first off,then if all else failed,psychiatry,or both.