It may be that in the larger design of the universe this invasion from Mars is not without its ultimate benefit for men; it has robbed us of that serene confidence in the future which is the most fruitful source of decadence, the gifts to human science it has brought are enormous, and it has done much to promote the conception of the commonweal of mankind.
There are no more uses of "decadent" in the book.
Show samples from other sources
So, sitting on the couch by myself, not talking, felt decadent.
Gillian Flynn -- Gone Girl
She slept decadently, eight to ten hours a day, could sleep anywhere—on a three-minute car ride, in the filthy booth of an off-campus diner, on anyone’s couch, at any time.