Stocks may struggle to beat autumn blues

Indeed, overall S&P 500 earnings estimates for the third quarter are fast eroding. And while oil prices are below their July peaks, they are still uncomfortably high for consumers and businesses.

On top of that, there's the U.S. presidential election, which heats up after Labor Day, which could add to volatility.

Meanwhile, U.S. economic fundamentals still look dismal, Johnson said, despite recent data showing gross domestic product grew at a surprisingly robust 3.3 percent clip in the second quarter.

"If you look at GDP, you're led to believe the economy is solid," he said. "But if you look at the variables -- employment, industrial production and personal income -- the economy does not look solid but weak."

And signs of sluggish growth beyond U.S. borders could spell trouble for a new host of sectors. After reporting a surprisingly steep slide in second-quarter profit this week, Dell Inc, the world's second largest computer maker, warned that companies are cutting back on technology spending worldwide.

BETTER TIMES AHEAD?

Of course, a struggling economy does not necessarily mean stocks have to swoon, as investors have in the past looked ahead to better times.

Giving stock investors some hope that the market may soon shake off the blues is the fact that October marks a year since the major U.S. stock indexes began their downward slump -- and, according to data from Ned Davis Research, bear markets typically last just over a year.

In 2002, even before the scandals surrounding Enron and WorldCom were sorted out, markets began to rally their way back into a bull market.

And with financial firms having reported more than $400 billion in credit-related write-downs over the past 12 months, some are hoping things can only get better from here.