In it to Quit: Commitment Contracts for Smoking Cessation (I2Q)

Last registered on September 11, 2018


Trial Information

General Information

In it to Quit: Commitment Contracts for Smoking Cessation (I2Q)
Initial registration date
November 19, 2015

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
November 19, 2015, 1:38 PM EST

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated
September 11, 2018, 10:28 AM EDT

Last updated is the most recent time when changes to the trial's registration were published.



Primary Investigator

Northwestern University

Other Primary Investigator(s)

PI Affiliation
Quinnipiac University and Weitzman Institute
PI Affiliation
Yale University
PI Affiliation
Yale University
PI Affiliation
Dartmouth College

Additional Trial Information

Start date
End date
Secondary IDs
This study aims to examine whether a combination of positive and negative commitment devices is effective at inducing long-term smoking cessation in smokers from a low-to-moderate income background. Investigators will randomly assign patients of a multi-site clinic in Connecticut to receive one or both of a succession of two commitment contracts. First, a two-month reward contract will pay participants for (a) engaging in clinic and web-based activities that support smoking cessation and (b) quitting smoking, as measured at period end. Second, a four-month deposit contract will invite participants to commit funds which they forfeit unless they abstain from smoking over the entire period. A random subset of participants will also have the option to pre-commit to the deposit contract at study enrollment. Reward payout and deposit recovery will be conditional on biochemical verification of self-reported abstinence. Investigators will conduct follow-up biochemical verification at 12 months to observe whether abstinence persists after removal of incentives. The primary outcome of interest will be continuous abstinence from smoking between months 2 and 12, i.e. biochemically verified abstinence at all three measurements. A short baseline and endline survey will also be administered to measure characteristics and outcomes related to smoking behavior.
External Link(s)

Registration Citation

Anderson, Daren et al. 2018. "In it to Quit: Commitment Contracts for Smoking Cessation (I2Q)." AEA RCT Registry. September 11.
Former Citation
Anderson, Daren et al. 2018. "In it to Quit: Commitment Contracts for Smoking Cessation (I2Q)." AEA RCT Registry. September 11.
Experimental Details


The study enrollment period will last one year, consisting of a six month intervention and a follow-up at month 12. The intervention will take place in two phases. In the first phase, 2/3 of participants will be randomly offered incentives for a period of 2 months (“rewards contract”). These participants accrue monetary rewards for (a) engaging in clinic and web-based activities that support smoking cessation (“process”) and (b) quitting smoking by period end (“outcome”). CHCI will administer CO breathalyzer and urine anabasine/anatabine tests to biochemically verify self-reports of smoking abstinence (“confirmatory test”). Participants who test positive for smoking forfeit all accrued process rewards and do not receive outcome rewards. Participants who test negative for smoking may redeem 100% of their Phase I rewards.
A random subset of rewards group members will have the option to roll a portion of their Phase I rewards into a Phase II deposit contract, lasting four months. One quarter of incentive group participants can “pre-commit” to the deposit contract during study enrollment, one quarter will only receive the deposit contract offer at Phase I end, and half will not receive the offer at all. Participants who form a deposit contract must achieve abstinence during the entire contractual period in order to recover their deposit at Phase II end. As in Phase I, self-reported abstinence will be biochemically verified.
At the conclusion of the enrollment year, all participants will be requested to visit the clinic to take a final confirmatory test. To observe whether smoking abstinence persists after removal of incentives, no performance incentives will be contingent on the result of the follow-up measurement at 12 months.
All study participants will be offered CHCI’s full menu of smoking cessation services (e.g. individual/group counseling, tobacco cessation medication management). However, participants randomized to the control group (no rewards contract) will neither receive incentives in Phase I nor a deposit contract in Phase II. They will not create a stickK account associated with the study, though they may sign up for the online service independently.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Primary Outcome Measure:
Smoking abstinence
The primary outcome of interest will be continous abstinence from smoking between months 2 and 12, i.e. biochemically verified abstinence art all three measurements (2,6, and 12 months post-enrollment).

Secondary Outcome Measure:
-Process Participation Rates
One secondary outcome will be rates of participation in the various activities promoted for aiding in smoking cessation i.e. counseling, journaling.

-Uptake of commitment contracts
The final secondary outcome will be the rates of acceptance of commitment contracts by patients offered these devices.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
We will use two-stage randomization to assign participants to one of four groups.
Stage 1: Randomly assign 2/3 of participants to receive Phase I reward contract for smoking cessation and 1/3 to receive no reward contract.
Stage 2: Of those assigned to Phase I reward contract, randomly assign 1/4 to receive Phase II deposit contract offer during enrollment (“pre-commitment”); 1/4 to receive the offer at Phase I end (no pre-commitment); and 1/2 to receive no offer.
The resulting four groups are as follows:
Group 1: Control - neither reward nor deposit contract (1/3 sample, n=500)
Group 2: Phase I rewards only (1/3 sample, n=500)
Group 3: Phase I rewards + Phase II deposit contract without pre-commitment (1/6 sample, n=250)
Group 4: Phase I rewards + Phase II deposit contract with pre-commitment (1/6 sample, n=250)
Experimental Design Details
Randomization Method
Randomization done on site on a computer
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
Sample size: planned number of observations
1500 individuals
Sample size (or number of clusters) by treatment arms
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
Community Health Center, Inc
IRB Approval Date
IRB Approval Number


Post Trial Information

Study Withdrawal

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Is the intervention completed?
Intervention Completion Date
October 17, 2016, 12:00 +00:00
Data Collection Complete
Data Collection Completion Date
October 07, 2017, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
Final Sample Size (or Number of Clusters) by Treatment Arms
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials