Background
Self-incentives offer a plausible alternative to paying smokers to quit but have not yet been tested in a randomized controlled trial.

Purpose
The present study tested whether, compared with a control group, prompting smokers explicitly to self-incentivize if they abstain from smoking for a week or a month encouraged sustained abstinence.

Method
One hundred and fifty-nine smokers were recruited from stop smoking clinics and randomized to an active control condition (asked to form a plan to quit, n = 65) or one of two intervention conditions in which they were asked to form implementation intentions designed to ensure that they incentivized themselves if they had not smoked at all by the end of (a) the week (n = 44) or (b) the month (n = 50). The main outcome measure was self-reported abstinence at 3- and 6-month follow-ups, which was biochemically verified at baseline and in a subsample at 3-month follow-up.

Results
At 3-month follow-up, 34% (15/44; p < .05, d = 0.45) and 36% (18/50; p < .05, d = 0.49) of smokers abstained in the weekly and monthly self-incentivizing conditions respectively, compared with 15% (10/65) in the control. The same pattern of findings was observed at 6-month follow-up: 30% (13/44; p < .05, d = 0.35), 34% (17/50; p < .05, d = 0.45) and 15% (10/65) of smokers remained abstinent in the two intervention groups and control group, respectively.

Conclusions
Ensuring that smokers self-incentivized boosted significantly the effectiveness of the stop smoking program. Self-incentivizing implementation intentions could be implemented at low cost with high public health “reach” to change many health behaviors beyond smoking.

Trial Registration
ISRCTN11610200.