Substance-Impaired Driving among emerging adults remains a significant public health concern and may be the single riskiest substance-related outcome among young adults. Brief Interventions (BIs) have been shown to reduce alcohol-impaired driving among this age group, but are not often implemented - despite their demonstrated efficacy - because it is not economically feasible to deliver in-person BIs to all emerging adult substance users. The present study will be the first to examine whether a text-messaging-based cannabis-impaired driving BI significantly decreases cannabis-impaired driving among emerging adult cannabis users compared to an informational control. Participants will be 240 emerging adults who endorse driving after cannabis use (or combined alcohol and cannabis use) at least three times in the past 3 months. After completing baseline measures, participants will be randomly assigned to receive either: a) substance use information, b) a substance-impaired driving personalized feedback intervention, or c) a substance-impaired driving personalized feedback intervention plus interactive text messages. Participants will complete outcome measures 3 and 6 months post-intervention. Repeated measures mixed modeling analyses will be used to determine whether the intervention significantly reduces substance-impaired driving over time. The project has two specific aims: 1) to evaluate a text based cannabis-impaired driving intervention in a randomized clinical trial, and 2) to determine whether the use of interactive text-messages sustains intervention effects over time.

Rates of substance-impaired driving remain especially high among emerging adults, and substance-related traffic accidents remain the leading cause of substance-related death in this age group. Although rates of alcohol-impaired driving (AI-driving) among emerging adults have begun to decrease, rates of driving after cannabis use (DACU) continue to rise. In addition, many emerging adults report simultaneous use of alcohol and cannabis, a behavior that has been shown to increase the odds of substance-impaired driving and results in substantially greater fatal crash risk. Brief Interventions (BIs) have been shown to decrease substance use and related problems.6 BIs attempt to identify and correct faulty normative beliefs and highlight personal consequences of substance use (such as driving after substance use). BIs typically consist of one or two individual therapeutic meetings delivered in motivational interviewing (MI) style and include personalized feedback (based on a series of questionnaires completed by the participant prior to their BI session). One reason why BIs have not been widely implemented- despite their demonstrated efficacy - is that it is not economically feasible for universities and community agencies to hire and train staff to deliver in-person BIs to all substance users, and very few emerging adults seek out substance prevention or treatment services available on campus or in the surrounding community. Innovative ways of delivering BIs to this at-risk population, in a manner that is both effective and economically feasible, need to be developed. Text messaging represents a particularly advantageous way to provide BIs as they can be highly personalized to the individual and allows for engagement and interaction between the interventionist and participant. Research indicates that emerging adults prefer text messages to telephone calls and emails and rate this medium positively. Given the high prevalence and fatal consequences of substance-impaired driving, highly accessible intervention approaches are imperative for reducing this extremely risky behavior.

In the past few years, a number of interventions using text-messaging to target substance use and problems have been developed and evaluated with reviews and meta-analyses suggesting that the majority of these interventions result in improved outcomes and warrant further large scale studies. Most of these interventions target overall substance use and problems and do not focus on specific risk behaviors, such as substance-impaired driving. We have developed and evaluated a mobile-based BI focused specifically on decreasing AI-driving among college students in a pilot trial. This study indicated that a brief, mobile-based AI-driving intervention including MI text messaging resulted in significantly greater reductions in AI-driving at the 3-month follow-up, compared to alcohol information alone. We modified the intervention to focus on driving after cannabis use and found that the intervention resulted in significantly greater increases in perceived dangerousness of DACU and significantly greater decreases in DACU compared to to an informational control condition. Importantly, several recent studies have demonstrated greater effectiveness of interventions that include personal contact vs. those that are fully automated. The present study provides an important bridge between in-person therapist delivered interventions and fully automated interventions by utilizing interactive text messaging with participants in order to enhance retention of intervention elements and provide tailored, individualized interaction. It is imperative to directly test whether the use of interactive text-messages decreases substance-impaired driving significantly more than personalized feedback alone.

The proposed study will extend promising pilot results by: (a) increasing power by recruiting 240 emerging adults reporting recent driving after cannabis use (DACU), (b) including a 6-month follow-up to determine whether intervention effects persist over time, (c) examining mediators of intervention outcomes (e.g., changes in cannabis-related cognitions), and (d) providing additional intervention content focused on decreasing driving after combined use of alcohol and cannabis. The overarching goal is to use mobile technology to reduce driving after substance use among emerging adult cannabis users.

We will conduct a 3-group trial with 240 emerging adults (ages 18-25; project 50% female; 20% minority) recruited from a community in the Southeastern United States.

Group 1: substance impaired driving personalized feedback Group 2: substance impaired driving personalized feedback and Motivational Interviewing (MI) interactive text messages Group 3: substance use information (control) Aim 1: Evaluate a text based substance-impaired driving intervention in a Randomized Clinical Trial.

Hypothesis 1: Group 2 will report greater reductions in driving after cannabis use and driving after simultaneous alcohol and cannabis use 3- and 6-months post-intervention.

Aim 2: Evaluate mechanisms of intervention response. Hypothesis 1: Cognitive factors (e.g., changes in perceptions of dangerousness and consequences, peer norms, cannabis expectancies) will mediate intervention outcomes.

Inclusion Criteria:

• Age 18 or older
• Ability to speak, read, and write in English
• Reports driving after using cannabis prior to driving at least three times in the past three months
• Reports having access to a motor vehicle, a valid driver's license, and plans to drive a vehicle in the next 6 months
• Reports access to a cell phone and willingness to read intervention material and exchange 3 texts post intervention with the study administrator
• Reports a valid email address

Exclusion Criteria:

• Currently in treatment for substance use

The final dataset will consist of self-reported data from survey questionnaires and qualitative data from text-messaging sessions. Preliminary data will be shared via a presentation at a national conference in the second and third years of the project. After all data is collected, a manuscript detailing findings from the study will be submitted for peer-review and de-identified data will be submitted to the NIDA data archive.

After all data is collected, a manuscript detailing findings from the study will be submitted for peer-review and de-identified data will be submitted to the NIDA data archive.