Studies support the theory that there are several causes, instead of a single environmental cause or genetic problem.

VOA: special.2009.01.06

Don't just stop in the middle of the street because everyone is coming right behind, and it's going to cause a problem.

请不要停留在街道中央，因为街上人来人往，
你的停留是会惹麻烦的。

在纽约的感受 - SpeakingMax英语口语达人

Scientists have believed that S.I.V.did not cause a similar immune system problem for primates.

VOA: special.2009.09.08

Anything you see as a problem can cause stress.

VOA: special.2009.03.24

Stuttering's cause has long been a mystery, but it has frequently been diagnosed as a psychological problem.

VOA: standard.2010.02.11