Testing the mHealth App Intervention for Nondaily Smokers "SiS4"

The present study is a large-scale (n=1,600) single-blind, remote, parallel, randomized clinical trial (RCT) comparing our app, the SiS app, to the NCI's smartphone app "QuitGuide". The RCT will be conducted entirely remotely, because the app is intended to be accessible to smokers nationally without need for in person contact. All participants will set a targeted smoking cessation quit date and will be instructed to use the provided app for 7 weeks, 1 week prior to and 6 weeks post-quit. Online surveys will be conducted at enrollment and follow-up occurring 2 weeks, 6 weeks, 3 months, 6 months and 12 months after the initially chosen quit date. The primary outcome measure will be 30-day point-prevalence abstinence (PPA) at 6 months post-quit. The investigator team developed the app, "Smiling instead of Smoking (SiS)," specifically for and in collaboration with people who smoke less than daily. This app uses a positive psychology approach, in line with their preference to focus on positive self-identity and wellness.

The investigators have rigorously and iteratively developed and tested this app in a series of small scale prior studies. Study 1 (2017P001106) demonstrated feasibility and acceptability when smokers were onboarded in person. Study 2 (2018P002699) demonstrated feasibility and acceptability when smokers were onboarded remotely, nationwide. Study 3 (NCT04672239) demonstrated the app's ability to engage nondaily smokers and showed proof-of-concept efficacy in a small, randomized trial, where participants using the SiS app had significantly higher self-efficacy, lower craving, and higher positive affect at the end of treatment, compared to controls.

In this large-scale efficacy trial, the primary outcome measure will be 30-day point-prevalence abstinence (PPA) at 6-month post quit. The aims of the study are:

Aim 1: Test the effectiveness of the SiS app to improve smoking cessation outcomes

• H1: 30-day PPA six months post quit will be higher for SiS compared to QuitGuide participants.
• H2: SiS participants will have higher 30-day PPA at end of treatment and 12 months post quit.

Aim 2: Examine mechanisms and moderators of change

• Using mediation modeling, the investigators will test if theorized mechanisms of change (i.e., self-efficacy, positive affect, or craving) account for observed effects on 30-day PPA six months post quit.
• (Exploratory aim:) Using moderated mediation models, the investigators will examine if socioeconomic status, race, and/or the presence of mental health conditions moderate the effectiveness of SiS or moderate the mediation effects outlined in aim 2a.

Exploratory Aim 3: Explore app usage patterns and their relationship to smoking cessation

• The investigators will identify patterns of overall app use, as identified by group-based trajectory modeling.
• The investigators will conduct a feature-level analysis of the apps (i.e., which features got used how often).
• The investigators will test if patterns of app use and/or feature use predict 30-day PPA six months post-quit.

If found to be efficacious, this study would provide the first evidence of an efficacious treatment (the SiS app) for people who smoke less than daily, for whom currently no treatment guidelines exist.

• 18 years of age or older
• Sufficiently fluent in English to read and comprehend intervention and assessment materials
• Owns a smartphone (Android or iOS only)
• Currently smokes less than daily but at least weekly
• Has smoked 100+ cigarettes lifetime
• Has current intention to quit smoking
• Currently resides in the US
• Can use online survey technology to complete surveys
• Can download, install and use a smartphone app