"Since 1972, in each ease in which the discretionary sector starts to underperform ... it has led to a near-term top on the S&P 500—or at least it leads to a period of consolidation—over something around six months. It's anywhere from three months on the low side to closer to 12 months on the long side," Adams said.
Either way, "this loss of discretionary [leadership] is pretty consequential to the broad market," she said. "When you're focused as a long-term investor, it's early to call this the end of the discretionary trade. But in the short run, I think it's something to watch, certainly."
Adams adds that historically, a slowdown in consumer discretionary stocks has tended "to forecast the first fed funds target rate increase by an average of three months. In every single case in which the discretionary sector has made a longer-term top relative to the S&P 500, the Fed has started raising rates shortly thereafter."
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And even as she grants that the discretionary sector's underperformance could be "giving us some sort of false signal right now," it's not the only reason Adams is concerned.
"The fact that small caps are not confirming the S&P kind of being back to testing new highs is a little bit of a concern," Adams said. "And the other thing I'd watch Is momentum and breadth. We watched our momentum peak on this market back in late December. Momentum failed to accelerate along with the acceleration in price recently, and breadth the very same. The number of stocks making 52-week highs has fallen as the market has held up here."
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All in all, "I wouldn't say that the market's going to fall out of bed here. But they certainly suggest we need to have a new stimulant sort of emerge in order to get stocks running any higher."
In 2013, Adams had the lowest year-end S&P 500 target on the street, at 1,440. And while she no longer predicts that stocks will fall dramatically, as she did in the back half of last year, Adams sees no reason for the market to rise further anytime soon.
—By CNBC's Alex Rosenberg.