Ecological momentary assessment of working memory under conditions of simultaneous marijuana and tobacco use

Background and aimsThe neuropsychological correlates of simultaneous marijuana and tobacco use are largely unknown, which is surprising as both substances have similar neural substrates and have opposing influences on working memory (WM). This study examined the effects of marijuana alone, tobacco alone and simultaneous marijuana and tobacco use on WM. DesignPrimary aims were tested using a within-subject design, controlling for multiple subject- and momentary-level confounds via ecological momentary assessment (EMA). SettingData collection occurred in the Chicago, USA area in participants' natural environments. ParticipantsParticipants were 287 community young adults from a larger natural history study, oversampled for ever smoking, all of whom event-recorded at least one substance use occasion during the study week. MeasurementsMomentary tobacco, marijuana and alcohol use were recorded during multiple EMA across 1 week of data capture. WM was assessed at the end of each EMA assessment. Contextual variables that may influence WM were recorded via EMA. FindingsThere were main effects for marijuana and tobacco: WM was poorer with marijuana [odds ratio (OR)=0.91, 95% confidence interval (CI)=0.84-0.99] and better with tobacco (OR=1.11, 95% CI=1.04-1.18). These effects were not qualified by an interaction (OR=1.03, 95% CI=0.84-1.26). Alcohol also reduced WM (OR=0.87, 95% CI=0.79-0.95), and the tobaccoxalcohol interaction was significant (OR=0.81, 95% CI=0.66-0.99), indicating that the facilitative effect of tobacco disappeared with concurrent alcohol use. ConclusionsRelative to when individuals did not use these substances, working memory decreased with acute marijuana and alcohol use and increased with acute tobacco use. However, the putative effect of marijuana on working memory and the facilitative effect of tobacco on working memory were no longer present when used simultaneously with tobacco and alcohol, respectively. Data suggest that tobacco use may compensate for working memory decrements from marijuana among young adults and highlight the importance of investigating further the negative impact of alcohol use on cognition.