Letters of Note has a interesting 1848 letter by Edagar Alan Poe to George Eveleth in which he writes that his bouts of drunkenness and his deteriorating health were due to his trying to cope with the prolonged illness of his wife, Virginia: "This 'evil' was the greatest which can befall a man."
You say —"Can you hint to me what was the terrible evil" which caused the irregularities so profoundly lamented?" Yes; I can do more than hint. This "evil" was the greatest which can befall a man. Six years ago, a wife, whom I loved as no man ever loved before, ruptured a blood-vessel in singing. Her life was despaired of. I took leave of her forever & underwent all the agonies of her death. She recovered partially and I again hoped. At the end of a year the vessel broke again — I went through precisely the same scene. Again in about a year afterward. Then again — again — again & even once again at varying intervals. Each time I felt all the agonies of her death — and at each accession of the disorder I loved her more dearly & clung to her life with more desperate pertinacity. But I am constitutionally sensitive — nervous in a very unusual degree. I became insane, with long intervals of horrible sanity. During these fits of absolute unconsciousness I drank, God only knows how often or how much. As a matter of course, my enemies referred the insanity to the drink rather than the drink to the insanity. I had indeed, nearly abandoned all hope of a permanent cure when I found one in the death of my wife. This I can & do endure as becomes a man — it was the horrible never-ending oscillation between hope & despair which I could not longer have endured without the total loss of reason. In the death of what was my life, then, I receive a new but — oh God! how melancholy an existence.