Publication Date

Spring 2022

Advisor(s) - Committee Chair

Jenni Teeters (Director), Matthew Woodward, Matthew Shake

Degree Program

Department of Psychological Sciences

Degree Type

Master of Science


Driving after cannabis use (DACU) has become an increasing public health concern specifically for the states that have legalized cannabis use. In a 2018 survey, 4.7% of U.S. residents reported driving while impaired by cannabis (Azofeifa et al., 2019). Previous research suggests that several skills are impaired following cannabis use, such as increased lane weaving, slowed reaction time, and distorted perceptions about external stimuli. This effect was seen to extend to frequent cannabis users who also demonstrated driving impairments despite heightened cannabis tolerance (Hartman & Huestis, 2013). With the increase in DACU it is crucial to understand the factors that lead to DACU. Several studies have demonstrated that peer norms surrounding DACU, perceptions of consequences, perceptions of dangerousness, and effect expectancies contribute to the decision to engage in DACU (McCarthy et al., 2007; Darke et al., 2004; King et al., 2020). However, it is still unclear which of these factors would be best to target in an intervention to reduce DACU. The present study aimed to address this by investigating if increasing negative effect expectancies mediates DACU intervention outcomes. The data analyzed for this study derived from the project TECH pilot study which utilized a brief mobile phone-based intervention that aimed to reduce DACU frequency in a sample of 38 young adults. To assess change in DACU and negative effect expectancies, participants completed surveys at baseline and at a three-month follow-up. Results indicated that while rates of DACU decreased from baseline to three-month follow-up, negative effect expectancies did not significantly change. Concerning if negative effect expectancies mediated DACU intervention outcomes, the results demonstrated that they did not significantly mediate intervention outcomes. This may be due to several reasons such as sample size or that another cognitive predictor of DACU such as perceptions of dangerousness may have mediated. The results from the current study fills a gap in literature surrounding interventions targeting effect expectancies as a way to mediate outcomes. Future research should examine this on a larger sample size, as well as including other cognitive predictors in the model to assess if one plays a stronger mediating role than another.


Clinical Psychology | Health Psychology | Substance Abuse and Addiction