Chart watcher debunks a major bitcoin theory amid its 50% plunge this year

As bitcoin goes, so goes the stock market. That mantra has gained popularity since the two moved in lockstep to reach new records in 2017. One chart watcher isn't so convinced the correlative theory holds water.

"Looking at last year and bitcoin was up over 1,000 percent, it was a great year for the equity market, and they said, "Well, they both went up together and perhaps they should go down together," Charlie Bilello, director of research at Pension Partners, said Thursday on CNBC's "Trading Nation."

A dual move lower did occur for a few weeks earlier this year, but that relationship has since broken down, says Bilello. The S&P 500 tumbled nearly 12 percent from its record high on Jan. 26 to its year-to-date intraday low on Feb. 9. Over that same period, bitcoin dropped 33 percent.

"Since then, really that relationship has collapsed. If we're looking at from the peak last December, bitcoin is down over 60 percent and the S&P over that period of time is actually up 4 percent," he said.

The long-term data is even more damning of the bitcoin-stocks theory, says Bilello.

"If we go back to 2010 when we have data on bitcoin and compare that to the S&P, we're finding a zero correlation over time," said Bilello. "Just because something has a zero correlation doesn't mean they won't move at times in the same direction."

During the last major bitcoin crash from December 2013 to January 2015, for example, the S&P 500 was up 12 percent while bitcoin fell 85 percent.

"What you have to separate is correlation from causation," said Bilello. "Is there a fundamental reason for stocks and cryptocurrencies moving together? I don't believe there is. When you look at stocks, obviously they're tied to earnings, they're tied to a long-term stream of earnings. Bitcoin is entirely tied to sentiment."

The reasoning behind the search for a correlation is understandable, added Bilello.

"People think that they're tied because there's risk appetite in markets, there's certainly risk appetite in bitcoin, risk appetite in equities," said Bilello. "But you really have to divorce that from the actual data."

A lack of correlation between the S&P 500 and bitcoin is good news for worried stock investors. Since hitting a record of nearly $20,000 last December, bitcoin prices have plunged to below $7,000.