Bitcoin, the highly volatile digital currency, is proving to be the new stock market indicator, influential investor Jeffrey Gundlach said, adding that this is hardly just a "gut feeling" given the recent price movements.

"Bitcoin closed at the low of the year last week, SPX (Standard & Poor's 500 Index) is now at the low of the year this week," Gundlach, known as Wall Street's "Bond King," told Reuters in an interview. "Bitcoin keeps leading."

For months, Gundlach, who oversees $119 billion at DoubleLine Capital, has asserted that bitcoin has become the "lead horse" of risk assets and that its previous plunges have had a cascading effect on other risk assets including equities and high-yield junk bonds.

On Monday, Gundlach added that bitcoin carries so much predictive power "because it was the poster child of the speculative mood late last year."

Bitcoin peaked in mid-December at just under $20,000. From December to early February it fell to around $6,600 then rebounded to $11,500 in early March. Since then, it has been on a steady decline but edged back on Monday at around $6,953.

"That (December) crash means the speculative mood got exhausted," he said. "The hip bone is connected to the thigh bone."

Gundlach said bitcoin's price went vertical starting around mid-September. The S&P 500 Index accelerated to the upside at exactly the same time, he said. "Bitcoin mania was reached in mid-December and it promptly started to crash."

The S&P frenzy, he said, continued on to Jan. 26 but "the bitcoin crash was shouting that the speculative mania of the social mood had already passed. Then the S&P collapsed, joining Bitcoin in gear on the downside."

But as the S&P was diving to its lows, bitcoin was already rallying, Gundlach noted. As a result, the S&P found a bottom and subsequently the tech-heavy Nasdaq even crawled back to a new high, he said. "But as that new high was being made, bitcoin was back in bear-market mode. Soon after it was tank time again for stocks.

"It is all tied together, obviously," Gundlach said.

In a January investor webcast, Gundlach said he believed the price on bitcoin had hit its peak. “The high for bitcoin is in,” he said. “It’s just a thing that is out there, unproven. I have a theory that bitcoin is very different than what people think. People think that it is tremendously safe and anonymous and can’t be hacked and all that stuff. I have feeling that it is the opposite.

“I do not own bitcoin. This type of investment is very, very different from my conservative DNA,” Gundlach said.