A Situational Examination of Neurocognition with Simultaneous Cannabis and Tobacco Use

Concurrent cannabis and tobacco use has become prominent among young adults, but research suggests that individuals who concurrently use both substances experience more problematic outcomes than single-substance or dual-substance (but not simultaneous) users. However, few studies have examined the neuropsychological correlates of combined use, despite cannabis and tobacco acting on similar brain regions and having opposing influences on working memory (WM). This is important to understand given that WM alterations might reinforce continued substance use and may serve as a barrier to quitting. This study examined performance on a novel WM task administered via ecological momentary assessment (EMA) during different substance use occasions among 287 young adults from a natural history study of the social-emotional contexts of smoking. It was hypothesized that compared to random times without substance use, WM would be enhanced with tobacco, impaired with cannabis, and not significantly different with simultaneous tobacco and cannabis. Additionally, it was hypothesized that EMA WM performance would be associated with performance on psychometrically-validated laboratory measures of WM, but not with other laboratory-based assessments of neurocognition. A mixed-effects regression model for repeated ordinal outcomes was fit to the data. Results revealed that individuals exhibited worse WM with cannabis and better WM with tobacco compared to non-using times. Additionally, cannabis was not associated with WM when used with tobacco. These effects emerged even after accounting for multiple subject- and momentary-level confounds. Spearman’s rank correlations were run between EMA WM performance and standardized measures of neuropsychological functioning among a study sub-sample. EMA task performance was positively correlated with predicted IQ, auditory WM, and visual WM, but was not related to other measures of neurocognition. Partial correlation coefficients were estimated using nonparametric methods between EMA task performance and indices of auditory and visual WM while controlling for predicted full scale IQ. The correlation between EMA performance and visual WM as well as auditory WM remained significant and trended toward significance, respectively. These study data provide information about the cognitive correlates of single and combined use of cannabis and tobacco as well as present feasibility data on the integration of traditional neurocognitive assessments into ambulatory paradigms.