That's what coroners used to rule, wasn't it? "...while the balance of his/her mind was disturbed" or similar phraseology? But maybe I'm unjustly maligning the coroner (must be a stressful job - has anyone on here been one?).
Anyway, consider this case, of an elderly lady (in her 90s) whom I knew. She lived in a private care home in Reigate, close to where my mother lived. This lady's daughter was a close friend of my mother's. The daughter lived in north London, and found it quite a trek to come and visit her mother, but she managed it fairly often (every two or three weeks I think) - she always used to pop in and see my mother after visiting her mother. OK - I suppose the old lady was reasonably well off in the circumstances, if perhaps somewhat bored with her lifestyle. From what I remember of her, late in her life, no sign of mental disorder - certainly not dementia or anything like that. But I'm no expert.
One day she evidently made up her mind. She carefully tidied up her room. She said a sort of veiled 'goodbye' to her friends in the home, and returned all the books and other items she'd borrowed from them. Then she went back to her upstairs bedroom and climbed out of the window.
My mother told me that it made the front page of the local rag. I don't know what the Coroner's verdict was.