The Wall Street bank's customers are now responding to geopolitical risks, trade tensions and a debate about where yields are headed, which has dampened market exuberance, he said. He also noted that the first quarter of the year tends to be the strongest for capital markets activity, which suggests profits through year-end may be less impressive.

"There are some flattering factors to the first quarter, including seasonality ... Our expectation is that the environment won't be as conducive going forward," said Pruzan.

Copyright Reuters, 2018