The U.S. is in one of the most volatile investment environments in decades, according to a top economist and risk expert. While some investors are jubilant about the stock market rebound, he is keeping an eye on a potential market crash.

Nassim Taleb, author of "The Black Swan," recently expressed concerns about market conditions in an interview. He said the current environment seems similar to past crashes, adding that he is focused on preparing for such an event.

"We have accumulated a lot of risk," the Universa Investments advisor said Friday. "I would say ... my focus is more on hedging against an eventual market crash because we are more vulnerable than at any time in the last 20, even 30 years," he later added.

Taleb noted that despite the stock market's gains over the past year, there are still some risks in the market.

He said stock prices look "crazy," noting that most of the S&P 500's gains have been concentrated in a handful of companies related to artificial intelligence.

However, he said it's unclear whether these companies have the greatest growth potential, pointing to the rotation of best-performing companies during the dot-com bubble. "AI is going to be the best investment. But maybe not these companies," he said.

At the same time, Taleb said the U.S. economy has been "confusing" and it is uncertain whether some industries are overheated.

Due to the increased globalization since the pandemic, the world economy is more interdependent. He pointed out that this means that external shocks are more likely to spread, which is also a factor that makes the investment environment more complicated.

Taleb said that the debt held by Western countries is "more than we can bear", and the U.S. debt-to-GDP ratio reached 124% at the end of September. He previously predicted that if high debt levels are combined with external shocks, it could lead to a "death spiral."

At the same time, investors are emerging from a period dominated by low interest rates. He pointed out that many market participants are accustomed to avoiding more "conservative" assets, and this risk-taking attitude may put traders in a vulnerable position.