A Cochrane review included 77 studies. Among smokers who contacted helplines, quit rates were higher for groups randomised to receive multiple sessions of call-back counselling (9 studies, >24 000 participants, RR for cessation at longest follow up 1.37, 95% CI 1.26 to 1.50). There was mixed evidence about whether increasing the number of calls altered quit rates but most trials used more than two calls. Three studies comparing different counselling approaches during a single quitline contact did not detect significant differences. Of three studies that provided access to a hotline two detected a significant benefit and one did not. Telephone counselling not initiated by calls to helplines also increased quitting (51 studies, > 30,000 participants, RR 1.27; 95% CI 1.20 to 1.36). In a meta-regression controlling for other factors the effect was estimated to be slightly larger if more calls were offered. The relative extra benefit of counselling was smaller when it was provided in addition to pharmacotherapy (usually nicotine replacement therapy) than when the control group only received self-help material or a brief intervention..
Comment: The quality of evidence is downgraded by study quality (inadequate or unclear allocation concealment).