"Even the 'winners on the [Antiques Roadshow] — those who make it on air, tell and receive stories, discover sudden wealth — are not delivered. On television we see only their whoops and blushes. Off the set, if given the chance, they will worry out loud about family squabbles, the cost of insurance, the threat of theft. They exhibit the same 'strange melancholy ... in the midst of their abundance' that Tocqueville noticed in 1831, the same strange melancholy of new billionaires in Silicon Valley diagnosed with 'Sudden Wealth Syndrome,' or lottery winners who descend into dysfunction."
—Joshua Wolf Shenk, "The Things We Carry," Harper's Magazine, June 2001

"Many tribes do not have the financial experience to manage money, nor do they have the necessary sophisticated planning," Adamson said. "These tribes are really being hard-pressed with the sudden-wealth syndrome. There is abuse and misuse in any community."
—William Flannery, "Native American Backs Reservation Business," St. Louis Post-Dispatch, March 3, 1997

Note, too, that there's a broader sense of this term that applies to larger entities such as companies and countries. This sense goes back quite a bit farther:

In his conversation with me, Kato further explained the "sudden wealth" syndrome: Japan has been a rich nation for only about 20 years, and needs another 20 before gaining the respect that wealth commands. —Hobart Rowen, "U.S. Should Accept Idea of Sharing Power With Japan, " The Washington Post, October 23, 1988