Tobacco may mask poorer episodic memory among young adult cannabis users.

Abstract

Objective Co-occurring cannabis and tobacco use has become increasingly prevalent among young adults, but it is not clear how tobacco use may alter the neurocognitive profile typically observed among cannabis users. Although there is substantial evidence citing cannabis and tobacco's individual impact on episodic memory and related brain structures, few studies have examined the impact of combined cannabis and tobacco use on memory. Method This investigation examined relationships between amount of past year cannabis and tobacco use on four different indices of episodic memory among a sample of young adults who identified cannabis as their drug of choice. Results Results indicated that more cannabis use was linked with poorer initial acquisition, total learning and delayed recall on the Hopkins Verbal Learning Test--Revised (HVLT-R), but only among cannabis users who sporadically smoked cigarettes in the past year. Conversely, amount of past year cannabis use was not associated with episodic memory performance among individuals who more consistently smoked cigarettes in the past year. These differences could not be explained by several relevant potential confounds. Conclusions These findings provide important insight into a potential mechanism (i.e., attenuation of cognitive decrements) that might reinforce use of both substances and hamper cessation attempts among cannabis users who also smoke cigarettes. Ongoing and future research will help to better understand how co-use of cannabis and tobacco impacts memory during acute intoxication and abstinence, and the stability of these associations over time.

Early onset marijuana use is associated with learning inefficiencies.

“…Results replicate a long line of prior work demonstrating poor delayed recall with marijuana use (e.g., Becker et al, 2014; Crane, Schuster, Mermelstein, & Gonzalez, 2015; Dougherty et al, 2013; Gonzalez et al, 2012; Hanson et al, 2010; Harvey, Sellman, Porter, & Frampton, 2007; Schuster, Crane, Mermelstein, & Gonzalez, 2015; Solowij et al, 2011). However, findings from this study point to the likely mechanism through which this effect occurs: learning.…”

Comorbid Cannabis and Tobacco Use in Adolescents and Adults

“…It has been suggested that one of the reason for increased prevalence of comorbid cannabis and tobacco use is due to the opposing effects exerted by the substances and that tobacco is used to mask the impairments that are associated with cannabis use[47]. For instance, in a study assessing episodic memory in cannabis and tobacco users, deficits in episodic memory were observed in cannabis users with intermittent tobacco use whereas no significant impairments were observed in cannabis users with consistent tobacco use[48]. Similarly, in a study by Jacobsen and colleagues, (2007), cannabis users with at least 60 episodes of cannabis use exhibited deficits in recalling learned words after a 25 minute delay compared to users with less than 40 lifetime episodes of cannabis use during abstinence from smoking conditions whereas in the smoking condition, no significant deficits were observed[49].…”

Differential associations of combined vs. isolated cannabis and nicotine on brain resting state networks

“…On the other hand, Bonn-Miller et al (2010) showed that nicotine-only individuals had greater symptoms of depression and anxiety relative to those with combined use groups (Bonn-Miller et al 2010). Cognitively, some suggest that the degree of combined use has differential effects such that those who primarily use cannabis but also sporadically use nicotine show wide-ranging impairment on cognitive function including learning and memory than those who use nicotine more regularly (Schuster et al 2015). The authors posit that greater combined use may attenuate cognitive deficits and therefore reinforce concurrent use.…”