Does regular cannabis use affect neuroanatomy? An updated systematic review and meta-analysis of structural neuroimaging studies
Lorenzetti et al.·European Archives of Psychiatry and Clinical NeuroscienceImpact 2.9
No direction reportedGRADEHigh123 citations
Samplek = 30 Studien
ControlNon-users
DesignSystematische Review + Meta-Analyse
”Key finding
Regular cannabis use was associated with measurable neuroanatomical changes in individual brain regions, though the data situation was heterogeneous.
Summary
SR + meta-analysis (k=30 studies, 17 meta-analyses) on neuroanatomical changes in regular cannabis use vs. controls. Significantly smaller hippocampal volumes (SMD=0.14, 95% CI [0.02, 0.27], p=0.02, I²=74%) and medial orbitofrontal cortex (SMD=0.30, 95% CI [0.15, 0.45], p=0.0001, I²=51%) in users. Findings consistent with neuronal vulnerability of psychosis-associated circuits (reward, learning, memory).
P
PopulationRegular cannabis users vs. non-users, n=30 studies with 106 effect sizes
I
InterventionRegular cannabis use (various duration and cumulative dose)
C
ControlNon-users (controls without cannabis exposure)
O
OutcomeSignificantly smaller volumes: hippocampus (SMD=0.14, p=0.02), medial OFC (SMD=0.30, p=0.0001), lateral OFC (SMD=0.19, p=0.002); no association with dose/duration
Confidence in the evidence
Very lowLowModerateHigh
High
The highest of four GRADE levels, the effect estimate is very reliable.
Regular cannabis use is associated with adverse cognitive and mental health outcomes that have been ascribed to aberrant neuroanatomy in brain regions densely innervated with cannabinoid receptors. Neuroanatomical differences between cannabis users and controls have been assessed in multiple structural magnetic resonance imaging (sMRI) studies. However, there is heterogeneity in the results leading to cautious interpretation of the data so far. We examined the sMRI evidence to date in human cannabis users, to establish more definitely whether neuroanatomical alterations are associated with regular cannabis use. The regional specificity and association with cannabis use indices (i.e. cumulative dosage, duration) were also explored. We systematically reviewed and meta-analysed published sMRI studies investigating regional brain volumes (cortical, subcortical and global) in cannabis users and non-user controls. Three electronic databases were searched (PubMed, Scopus, and PsycINFO). A total of 17 meta-analyses were conducted (one for each cortical, subcortical and global volume) using the generic inverse variance method, whereby standardised mean difference in volume was calculated between users and non-users. Exploratory meta-regressions were conducted to investigate the association between cannabis use indices and regional brain volumes. A total of 30 articles were eligible for inclusion, contributing 106 effect sizes across 17 meta-analyses. Regular cannabis users had significantly smaller volumes of the hippocampus (SMD = 0.14, 95% CIs [0.02, 0.27]; Z = 2.29, p = 0.02, I<sup>2</sup> = 74%) and orbitofrontal cortex {medial (SMD = 0.30, 95% CIs [0.15, 0.45]; Z = 3.89, p = 0.0001, I<sup>2</sup> = 51%), lateral (SMD = 0.19, 95% CIs [0.07, 0.32]; Z = 3.10, p = 0.002, I<sup>2</sup> = 26%)} relative to controls. The volumes of the hippocampus and orbitofrontal cortex were not significantly associated with cannabis duration and dosage. Our findings are consistent with evidence of aberrance in brain regions involved in reward, learning and memory, and motivation circuits in the regular use of substances other than cannabis, pointing to commonality in neurobiological abnormalities between regular users of cannabis and of other substances.