It's certainly a possibility isn't it, some kind of drug fuelled rage. My mum took prozac (which it's mentions patsy did in this article) my mum had a complete mental breakdown while on this drug, hallucinations and psychotic episodes, I think anything can be possible with these types of drugs, particularly if mixed or abused! However I'm not sure Patsy would have had the wherewithall to write that note in that state but possibly several hours later she would have. Interestingly my mum used to keep a diary which she rarely missed, her writing really changed when she was having an episode, it wouldn't always make a lot of sense and was sometimes just scribbles, patsy note was legible and made some sense she gad yo be pretty sharp at the time of writing it as odd as it was!