Flexing its muscle.

NEW YORK (MarketWatch) — The U.S. dollar’s strong rise is getting a lot of the blame for the stock market’s recent weakness, but there’s more to it than a simple inverse relationship between the U.S. currency and equities.

The chart below shows that stocks and the dollar can move in the same direction or opposite each other for long stretches, including since the beginning of the dollar bull market in April 2011:

At the same time, this chart from Jones Trading shows that, on a monthly basis, the dollar and equities have tended to move in opposite directions since 2000:

The ICE dollar index DXY, +0.49%  , a measure of the U.S. currency against six major rivals, is up 4.4% since the beginning of the January, reaching its highest level in more than 11 years. The S&P 500 SPX, -1.35%  has slipped around 1.3% over the same period but remains not far from an all-time high.

While a surging dollar is an ever bigger potential headwind the more a company depends on overseas revenue, that’s far from the whole story when it comes to overall equity performance. It really depends on the reason the dollar is rising.

If it’s because the U.S. economy is going gangbusters (think the 1990s), stocks can gain, but if the greenback is rising due to a flight to safety, then, naturally, stocks suffer. See: Why a stronger dollar won’t suck the wind out of stocks.

One problem is that, right now, the dollar’s strength isn’t merely about the relative strength of the U.S. economy.

‘Rising international systemic risk’

Lena Komileva, chief economist at G-plus Economics in London, argued in a note back on Jan. 16 that the dollar’s recent performance reflects growing global anxiety.

Actions by players ranging from OPEC to the Swiss National Bank to the European Central Bank are giving investors anxiety pangs as they fret over whether the measures will succeed in meeting policy aims or will result in unintended consequences, she said.