The paragraph is followed by an incomplete phrase or sentence which summarizes the main idea of the paragraph. Choose the missing words of the phrase or sentence.

The benefits of quitting smoking - reduced risk of cancer and many other health problems - are known. But for millions of smokers, the calming effect of a cigarette can be reason enough to start up again. Studies have found, however, that in reality, lighting up has the opposite effect, causing long-term stress levels to rise, not fall.
Smoking may well cause rather than （） stress.