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Commit to Quit: Commitment Contracts for Smoking Cessation (C2Q)
Last registered on September 19, 2018

Pre-Trial

Trial Information
General Information
Title
Commit to Quit: Commitment Contracts for Smoking Cessation (C2Q)
RCT ID
AEARCTR-0003313
Initial registration date
September 13, 2018
Last updated
September 19, 2018 9:43 PM EDT
Location(s)
Region
Primary Investigator
Affiliation
Other Primary Investigator(s)
PI Affiliation
Carnegie Mellon University
PI Affiliation
Northwestern University
Additional Trial Information
Status
In development
Start date
2018-09-01
End date
2020-08-31
Secondary IDs
Abstract
This study will examine how advance commitment to a commitment contract impacts smoking cessation rates, by affecting the likelihood of taking up a commitment contract. By shifting the decision to start a commitment contract into an earlier time period, the option of pre-commitment negates the effect that present bias can have on the decision to commit in the moment. Thus, we expect that pre-commitment will increase the likelihood of an individual agreeing to a contract in the future, thereby increasing quit rates. This study design is an adjustment of our previous smoking cessation study and takes into account recent developments in the literature on the effectiveness of rewards and deposit contracts on smoking cessation, as well as learnings from a previous iteration of the study.
We will recruit smokers from a general population in the Chicago metropolitan area and randomly assign respondents to one of four groups: a control group, a treatment group offered a deposit contract (a form of commitment contract) for smoking cessation, a second treatment group offered the option to pre-commit, a month in advance, to a deposit contract for smoking cessation, or a fourth group offered a deposit contract, and then if the offer is declined, offered the option to pre-commit. Further, we will provide causal evidence on how awareness that commitment contracts can assist with smoking cessation affects demand for commitment contracts.
Deposit recovery will be conditional on biochemical verification of self-reported smoking cessation. The primary outcomes of interest will be cessation long-term, at 8 months after study start, or 6 months after the interventions end. A short baseline and endline survey will also be administered to measure characteristics and outcomes related to smoking behaviour.
External Link(s)
Registration Citation
Citation
Horn, Samantha, Dean Karlan and Jonathan Zinman. 2018. "Commit to Quit: Commitment Contracts for Smoking Cessation (C2Q)." AEA RCT Registry. September 19. https://doi.org/10.1257/rct.3313-1.0.
Former Citation
Horn, Samantha et al. 2018. "Commit to Quit: Commitment Contracts for Smoking Cessation (C2Q)." AEA RCT Registry. September 19. http://www.socialscienceregistry.org/trials/3313/history/34379.
Experimental Details
Interventions
Intervention(s)
The study period will last 8 months, consisting of a one- to two-month intervention, and a 6-month follow-up falling after the end of the pre-committed contracts. Six-months is used as the definition of a “long-term follow-up” in a recent Cochrane review on rewards for smoking cessation, and thus we view this as an appropriate time period for follow-up. Given the difference in contract start date across treatments, endline will either be 6 or 7 months after an individual’s commitment contract ends, depending on their treatment assignment.
Respondents recruited into the study will be randomized into one of four study arms. Respondents in the first treatment arm, the commitment group, will be offered a deposit contract. As part of the contract, respondents will be asked to pay their own money to the study team account, on the condition that they will only receive their money back after a month if they can verify that they have quit smoking with a biochemical test at a Quest diagnostics centre.
Respondents in the second treatment arm, the pre-commitment group, will be asked at baseline if they want to agree to start a deposit contract with the same terms as the first treatment arm, but starting in a month’s time. The third treatment arm is a combination of the first and second arm. Respondents in the third treatment arm will be offered a deposit contract at baseline. Then, any respondents who decline the offer, will be asked, in a replica of the situation in the pre-commitment group, if they want to agree to start a deposit contract with the same terms as the first treatment arm, but starting in a month’s time. The fourth arm will serve as a control group, and respondents in this arm will receive no offer for a deposit contract.
To address the question on whether a lack of information on the effectiveness negatively drives take up, and ultimately hinders smoking cessation success, we will cross randomize all treatments with an information module. The information module will be brief and contain easy-to-digest statistics on the effectiveness of commitment contracts for smoking cessation among individuals who agree to such contracts. The most relevant statistics from which to draw this information come from Halpen et al (2015) which tests the effects of commitment contracts with a large sample.
All study respondents will take part in a baseline at the start of the study and an endline survey 8 months after the start of the study. Further, any respondents who have a deposit contract will be asked to verify their smoking status at the end of their month long commitment period. All surveys, and requests for smoking status, will be administered remotely through Qualtrics, which can be accessed on a computer or a smartphone via the internet. As noted above, being able to access the internet will be an inclusion requirement for the study. All study payments will be processed through Paypal, and all payments into deposit contracts will also be made via Paypal.
All respondents will be asked their smoking status at endline. We will request that any self-reported claim of smoking cessation is verified biochemically with a urine anatabine test at a Quest diagnostics lab. All respondents who self-report that they have quit smoking will be paid for visiting the lab, and arrangements will be made with Quest to ensure that respondents will not be responsible for payment when attending the lab. The study team has already discussed the necessary set up with the Quest diagnostics team and we do not see this being a barrier to study success.
Intervention Start Date
2019-01-01
Intervention End Date
2020-01-01
Primary Outcomes
Primary Outcomes (end points)
Smoking abstinence
Primary Outcomes (explanation)
The primary outcomes of interest will be cessation long-term, at 8 months after study start, or 6 months after the interventions end.
Secondary Outcomes
Secondary Outcomes (end points)
Process Participation Rates
Acceptance Rate of Commitment Contracts
Secondary Outcomes (explanation)
One secondary outcome will be rates of participation in the various activities promoted for aiding in smoking cessation i.e. counseling, journaling.
The final secondary outcome will be the rates of acceptance of commitment contracts by patients offered these devices.
Experimental Design
Experimental Design
We use a randomized controlled study to compare the effectiveness of commitment, and pre-commitment for smoking cessation. Respondents will be randomized to one of four groups:
Group 1: Control – no deposit contract
Group 2: Deposit contract without pre-commitment
Group 3: Deposit contract with pre-commitment
Group 4: First offered deposit contract without pre-commitment. Then, if not taken up, offered deposit contract with pre-commitment.
We will then further cross randomize respondents in each treatment group to either receive, or not receive, with a 50/50 split, information on the positive effects of deposit contracts for smoking cessation. The primary study outcome will be smoking cessation 8 months after study start, defined as biochemical confirmation of self-reported smoking cessation. We will conduct a short baseline and endline survey with participants to assess the impact of the intervention on outcomes related to smoking behavior. In our analysis, we will deal with attrition by assuming those who leave the study continue to smoke. This is generally considered the conservative assumption and is in line with other studies (e.g. Gine et al, 2010, and Volpp 2006 and 2009).
Experimental Design Details
Randomization Method
Randomization done on site on a computer
Randomization Unit
Individual
Was the treatment clustered?
No
Experiment Characteristics
Sample size: planned number of clusters
1800 individuals
Sample size: planned number of observations
1800 inidividuals
Sample size (or number of clusters) by treatment arms
450 people with no deposit contract. 450 people offered deposit contract without pre-commitment. 450 people offered deposit contract with pre-commitment. 450 people offered deposit contract without pre-commitment first, then will be offered deposit contract with pre-commitment if not taken up/
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB
INSTITUTIONAL REVIEW BOARDS (IRBs)
IRB Name
IRB Approval Date
IRB Approval Number
Post-Trial
Post Trial Information
Study Withdrawal
Intervention
Is the intervention completed?
No
Is data collection complete?
Data Publication
Data Publication
Is public data available?
No
Program Files
Program Files
Reports, Papers & Other Materials
Relevant Paper(s)
REPORTS & OTHER MATERIALS