Neuropsychological deficits associated with cannabis use in young adults

Abstract

Background Cannabis is the most widely used illicit substance and has been associated with cognitive impairment. It is unclear whether such impairment can occur in the absence of potential confounding influences of co-morbid axis-I disorders and use of other illicit substances. Method Young adult volunteers (18–29 years) were recruited from the general community on the basis of having no axis-I disorders or history of illicit substance use other than cannabis use. Subjects were then grouped according to presence or absence of cannabis use (>1 time/week over past 12 months). Cognition was compared between groups using selected paradigms from the CANTAB. Results Cannabis users (n=16) and controls (n=214) did not differ significantly on salient demographic characteristics. Compared to controls, cannabis users showed significant impairments on quality of decision-making (Cambridge Gamble task), and executive planning (One Touch Stockings of Cambridge task). Response inhibition, spatial working memory, and sustained attention were intact. Conclusions This study identified cognitive deficits in cannabis users even in the absence of axis-I disorders and a history of using other illicit drugs. Future work should use longitudinal designs to track whether these deficits predate cannabis use or are due to its consumption.

Impact of adolescent marijuana use on intelligence: Results from two longitudinal twin studies

“…Differences between marijuana user groups have appeared in these other cognitive domains (18,23,57,58). Nevertheless, there is no reason to expect such a difference would emerge in the present study.…”

Activation of cannabinoid system in anterior cingulate cortex and orbitofrontal cortex modulates cost-benefit decision making

“…There is considerable evidence implicating the use of various cannabis derivatives in altered cognition and decision making, including risk taking behavior, irrational (or excessive) gambling, as well as impulsive and apathetic patterns of choice. This evidence comes mainly from human studies (Dougherty et al 2013;Grant et al 2012;Hermann et al 2009;Lane et al 2005;Moreno et al 2012;Solowij et al 2012;Whitlow et al 2004) and related work in animals (Boomhower et al 2013;Egerton et al 2006;Egerton et al 2005;Mishima et al 2002) that largely concurs with the results of the human studies. The role of cannabinoid signaling in decision-making pathways and the involvement of cannabinoid receptors in frontal cortical circuits of decision making have not received much attention to date.…”

Systematic review of ERP and fMRI studies investigating inhibitory control and error processing in people

“…81,82 Neither fMRI study found inhibitory control deficits in individuals with cannabis dependence (using go/no-go tasks), which is line with the results of nonimaging studies in similar populations. 83,84 However, individuals actively using cannabis showed increased activation during inhibitory control relative to controls in the ACC/pre-SMA, right IPL and putamen. 81 These findings can be interpreted as a compensatory neural mechanism, given that individuals with cannabis dependence did not show behavioural deficits.…”