Effects of regular cannabis use on neurocognition, brain structure, and function: a systematic review of findings in adults

Abstract

Although there are several limitations for study comparison and substantial heterogeneity in the findings, the present review suggests that regular cannabis use is associated with mild cognitive changes in addition to structural and functional alterations in the brain in adults. The morphological alterations could ultimately affect brain organization and function, but the associated time course for neuronal recovery as well as the real impact on cognitive functioning remain unknown. Also, it is still unclear whether the identified alterations are as a consequence of or precede cannabis use.

Cannabis Use Disorder

“…All of these CB1-rich areas serve core functions in memory, attention, learning and reward and cognitive control. The hippocampus, PFC and amygdala are central in cognitive processing, indeed behavioral/functional impairments are noted in memory, attention and learning in CUD [49].…”

“…Although the findings are mixed, overall subtle neurocognitive deficits in executive function, memory and learning are found with cannabis exposure, however, long term cannabis effects, and whether they are reversible, are still unclear [49,50]. The ability to hold and manipulate information is consistently impaired with acute cannabis administration, although few studies report long-term working memory problems [50][51][52][53].…”

“…Additionally, different measures of intake (i.e., inhaling, vaping, with/without tobacco) can also influence THC release/metabolism. Given all of the uncertainty between exposure parameters and neural substrates, many researchers are now calling for standardization of cannabis use metrics, particularly as the drug's effects appear more closely linked to dosage than duration of use [49]. Questions for future research include: (1) understanding CB1 receptor changes and relationships with reward, motivation, craving and abstinence, (2) clarifying cognitive and motivational alterations and whether these are precursors or consequences of CUD and (3) understanding the links between cannabis use and psychotic disorders.…”

Cannabis Use is Associated with Lower Hippocampus and Amygdala Volume: High-Resolution Segmentation of Structural Subfields in a Large Non-clinical Sample

“…Furthermore, research suggests that, as cannabis has increased in potency (i.e., increasing content of tetrahydrocannabinol [THC] and decreasing content of cannabidiol [CBD]) 2 , that the effects of cannabis on the brain structure may be increasing as well 3 . One effect of cannabis on the brain that has been repeatedly demonstrated is lower levels of gray matter volume in the hippocampus in cannabis users 4 . This has been found across in contexts and populations, albeit typically in very heavy users in small samples [5][6][7] .…”

Increased Resting State Triple Network Functional Connectivity in Undergraduate Problematic Cannabis Users: A Preliminary EEG Coherence Study

“…Similarly, human neuroimaging studies have shown that problematic cannabis use is related to different structural, functional, and neurophysiological brain alterations [7]. For instance, structural neuroimaging studies showed abnormalities in hippocampus volume and gray matter density associated with cannabis use [8]. Furthermore, Moreno-Alcázar et al [9] recently reported that, compared to healthy controls, long-term heavy cannabis users showed increased gray matter volume in the basal ganglia and nucleus accumbens.…”