I'm a bit late to the newer posts, but all the discussion about the meds Peter Miles was taking reminded me of a conversation I had a while back that may or may not be helpful here.
I was asking my brother, who is a psycologist, how to help a friend who was confiding some dark stuff to me. I ended up having to cut ties with her for my own health and sanity, unfortunately, but how she explained her worsening suicidal thoughts when taking antidepressants offers a lot of insight, to me anyways. And my brother confirming it as a common occurrence kind of made it make sense (as much as it can).
My friend had a nearly lifelong history of severe depression and suicidal ideation, and had been institutionalised on two occasions for recurrent suicide attempts. She was high functioning, maintained a job and acted totally normal, aside from the fact that once her meds started to work she suddenly had the energy and mental clarity to plan and carry out suucide.
So the medications were doing what they are designed to do- restore clarity of thought and the ability to be functional and carry out plans and activities. Usually this allows people to carry on with life and meet normal goals, etc. But in some instances it just applies that functionality to the suicidal thoughts they had previously been unable to follow through with.
Not sure if that made any coherent sense, I'm really tired... But it reminded me of when AC had said that he "believed Peter had been planning this for a long time." That might actually have been the case and the antidepressants worked in such a way he was able to carry out that plan.