The latest confidence reading of millionaires hit its lowest level since June 2009, according to Spectrem Group.

The company's Millionaire Investor Confidence Index dropped 11 points in August, for a reading of minus 18. The index hadn't been that low since it hit minus 20 last summer. The index is now in mildly bearish territory after 12 consecutive months in neutral.

Elsewhere, the Spectrem Affluent Investor Confidence Index that measures the investment confidence and outlook of households with $500,000 or more in investable assets, fell 4 points in August, its third consecutive monthly decline. It, too, is in mildly bearish territory.

"The millionaires' decline is particularly troubling since it suggests millionaires, typically more sophisticated than the broader affluent population, are reverting to a bearish frame of mind," said George H. Walper, Jr., Spectrem Group's president.

When asked an open-ended question about what news story most affected their economic outlook, respondents listed the political environment (18%); unemployment (16%); the economy (11%); stock market conditions (8%); health care reform (5%); the oil spill (2%); and European problems (1%).