Results:
We found 53 studies with a total of over 25,000 participants. One very large study found a large benefit. It gave intensive support including nicotine gum, multiple group sessions, and long term contact to help people stay quit or encourage additional quit attempts. Because it was not typical of most treatment programmes, it was not included when we estimated the likely benefit, although it shows that such intensive support can be very effective. Based on the remaining 52 studies, we found high quality evidence that using a combination of behavioural support and medication increases the chances of successfully quitting after at least six months. Combining the results suggests that the chance of success is increased by 70 to 100 percent compared to just brief advice or support. There was some evidence that the effect tended to be larger when participants were recruited in healthcare settings. There was no clear evidence that providing more contact increased the number of people who quit smoking at six months or longer. .