PROVIDENCE, Rhode Island (Reuters) -Trillions of dollars in market prices alternately have been wiped off and added back to portfolios, leading to high anxiety among investors and a move by some to dial down risky positions as they wait to see how the Trump administration's policy on tariffs shakes out.

The rollercoaster ride of the last week has been nervewracking for both retail and institutional investors. It shows that the back-and-forth over tariffs which caused such huge market moves has come at a cost.

"This is bonkers," said Jim Carroll, senior wealth advisor and portfolio manager at Ballast Rock Private Wealth in Charleston, South Carolina. "I think a lot of retail clients, talking to their advisors after this latest downturn, are saying, just get me out of the way of this landslide and we can come back later. What they're feeling is an unusual degree of anxiety."

The constant market swings have caused daily dilemmas among clients, Carroll said.

"I'm talking to our own clients every day, who do have some unrealized losses as a result of this," said Carroll. Those clients are constantly asking whether to sell or hold.

While a sudden market rally on Wednesday restored equity levels nearly to where they had started, it only held briefly.

Wednesday's mammoth gains -- some of the largest seen in the last five years -- left 98% of stocks in the Standard & Poor's 500 Index in positive territory, said Adam Turnquist, chief technical strategist at LPL Financial. The selloff that followed on Thursday left 86% of the same group of stocks in the red, he added.

"Customers are all feeling pain, because we were down hugely before yesterday, then up huge yesterday, and now we're back down again," said Malcolm Polley, chief market strategist at Stratos Investment Management in Beachwood, Ohio, on Thursday. "There are a lot of emotions going on and it makes people nervous, some of them get nauseous."

In a research report published on Thursday, BTIG compared prior periods of volatility with what the firm's analysts described as "choppy bottoms". In this pattern, they noted, stock prices moved back and forth with big swings, while at the same time staying within a defined trading range. Ultimately, markets hit a true bottom and revived, usually after a few months, the report said.

"We think this environment will be similar," BTIG analysts said in the report. "The key is to not get emotional at the extremes."

CONFUSION ON PATH AHEAD

Part of the anxiety stems from the lack of information and predictability investors want, making it more challenging for them to set aside emotions when making investment decisions.

"A 90-day reprieve on tariffs is three more months of uncertainty in which anything could happen," said Linda Duessel, senior equity strategist at Federated Hermes.

She says she needs to update a presentation that she had been giving to financial advisors as recently as April 1 in light of the events. In that, she explained that she saw no problems with forward-looking earnings, employment, or the economy more broadly. "I definitely need to update it big-time -- but with what?"

Many investors say their models are less helpful in making decisions when a single comment from President Donald Trump can trigger a selloff or a big rally.

Hasty reactions to headlines frequently reverse as a more considered view is taken, or positions are unwound, they added.

Andrew Graham, founder and managing partner of Jackson Square Capital in San Francisco, said he has seen cash levels climb in client portfolios to as much as 20% to 50%, as he has overseen sales of some money losing positions.

"That makes me nervous," he said. "Clients are OK with being on the sidelines right now, but I'm aware that they are fearful until they are not, and then they want to see that I'm delivering performance on the way up again."

The difference in investor type also leads to different behavior, advisors say.

"Active traders are finding a lot of opportunities in these big moves," said Justin Zacks, vice president for strategy for North America at trading platform moomoo, which is dominated by retail traders, including those from Asia.

"Longer-term investors, who concentrate on fundamentals, are thinking about whether and how to reposition or add a little more cash or get more defensive and rotate."

Zacks said he is urging clients who ask him questions to dial into earnings conference calls and look for insight into the future by watching to see if CEOs scale back capital spending or announce other plans or thoughts about the tariffs.

Other advisors said they were also searching for answers.

"When the uncertainty is this high, I don't have a clue what will be happening next," said Carroll.

Polley said the key is to not panic.

"My blood pressure never spikes," said Polley. "You have to become like Spock, with ice water in your veins. Your enemy is emotion."