I think that there are as many answers to this question as there are artists--Ginsberg's mother deteriorated from being functional and productive to institutionalization--I don't know if here affliction contributed to his creativity, but it did open him to the schizophrenic visions of Carl Solomon, which he framed in Howl, and it made it possible for him to sustain a friendship with Jack Kerouac, when others had abandoned him as he deteriorated into torment--


Kerouac shows, to me anyway, that the creativity is in spite of and not because of, the madness--
If you read him chronolgically, you can see his energy and vitality slowly eaten away, until, in his finally works, he is an empty shell, trying to imitate himself in better days.