HONG KONG — There are all sorts of reasons for the Hong Kong stock market to have the jitters these days. The Chinese economy remains wobbly. North Korea is threatening nuclear war. And perhaps most worrisome this week, a leading Hong Kong actor has a new movie coming out.

Hong Kong investors call it the Ting Hai effect: When the actor Adam Cheng has a new television show or a new movie, the Hang Seng index often takes a dramatic turn for the worse. And in a city where superstitions can guide daily routines, the financial sector is worried.

Mr. Cheng’s new movie, “Saving General Yang,” has its debut in theaters Wednesday, and investors in the Hong Kong market, which has been generally buoyant of late, are on guard, while acknowledging that it is unlikely that a movie opening could drive a major market index.

“Of course, investors need to be wary to an extent,” said Thomas Wong, a Hong Kong banker. “That is part of the job, but they shouldn’t let a movie decide whether the stock market will do well or not. That is not how the market works. People may talk about it, but they are not going to take it seriously.”