Stress and anxiety caused by the sudden accumulation of unaccustomed wealth.
"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
It is dashedly but not all at surprisingly difficult to find a commentator who feels even the slightest pity for someone who "suffers" (they always put "suffers" in quotation marks) from sudden wealth syndrome. The more likely reaction is snide sarcasm or even outright derision. Apparently, it remains lonely (and somewhat stressful) at the top.
The "wealth" part of sudden wealth syndrome has normally been associated with the riches accumulated from dot-com IPOs and the rapid rise of the Nasdaq stock market in the late 90s. However, it also applies to lottery winners, estate heirs, and people whose get-rich-quick schemes actually worked.
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