Structural neuroimaging in polysubstance users

Abstract

The simultaneous and/or concurrent use of licit and illicit substances (polysubstance use, PSU) is most common today. Structural magnetic resonance imaging (MRI) has been applied extensively to study individuals ostensibly using a single substance. These studies have produced a picture of regional gray matter and white matter alterations with each substance or class of substances. Very few studies measured regional brain morphometry in today’s polysubstance users. This limited data suggest morphometric alterations with PSU that are not simply additive but often different from those of monosubstance users. Specifically, subcortical volume enlargements are observed that may be tied to mechanisms that also oppose volume reductions in cortical brain regions, thereby underestimating actual cortical atrophy. The complex actions of polysubstance use on brain structure and function need greater scrutiny with strong methodological approaches to inform more efficient treatment of polysubstance users.

Subcortical surface morphometry in substance dependence: An ENIGMA addiction working group study

“…Neuroimaging research over the years has attempted to elucidate brain‐based biomarkers (ie, structure, function, and neurochemistry) that may indicate aberrant processes in dependence on various substances 5 . Separately, these studies have demonstrated volumetric differences in common subcortical structures, including the hippocampus, amygdala, striatum, and thalamus, in opioid, stimulant, alcohol, tobacco, and cannabis use disorders 6–10 . Such findings are consistent with the proposed role of these striatal and limbic structures in supporting processes (eg, planning and decision‐making, reward, and memory) crucially involved in the etiology of substance use and dependence 11,12 .…”

“…The individual effects of other illicit substances on brain morphology may be subtler than previously assumed. 6,7,10 The smoking-related effect was not only observed between nicotine dependence and nonsmoking controls but also between smoking controls (who were not diagnosed with a nicotine dependence) and nonsmoking controls, suggesting structural differences associated with use rather than dependence. The proposed exposure-related effect (as opposed to dependence-related effect) of cigarette smoking is supported by a study demonstrating a dose-dependent relationship between nicotine use and enlarged putamen volume.…”

“…Subcortical morphometry may be subject to an interactive effect between nicotine and other substance use. For example, the typically observed subcortical differences in users dependent on methamphetamine, cocaine, or cannabis6,7,10 may have been counteracted by an opposing cigarette-smoking effect. Unfortunately, the low number of methamphetamine-, cocaine-, or cannabis-dependent subjects who are also nonsmokers, and the lack of well-characterized smoking level information within these substance-dependent users prevents an interrogation of the interactive effect between cigarette smoking and other substance use/dependence in brain structural effects.A key structure emerging from this comprehensive examination of substance-related subcortical morphology is the hippocampus, being notably implicated (up to >40% of the structure's surface) across the examined models.…”

Concurrent and Simultaneous Use of Cannabis and Tobacco and Its Relationship with Academic Achievement amongst University Students

“…Acute memory is needed to function and succeed in a university environment. However, a recent investigation concluded that the complex actions of polydrug use (concurrent and simultaneous use) on the brain structure and function need greater examination [ 50 ]. (2) Concurrent and simultaneous use of cannabis and tobacco could be a consequence of poor GPA.…”

Cingulate Cortex Structural Alterations in Substance Use Disorder Psychiatric Inpatients

“…Previous meta-analyses have found volumetric differences in subcortical structures, including the hippocampus, amygdala, striatum, and thalamus and several brain regions, such as the prefrontal cortex (PFC), anterior cingulate cortex (ACC), and insula, in substance-dependent individuals. [3][4][5] Additionally, The Psychiatric Genomic Consortium (PGC)-Enhancing Neuroimaging Genetics through Meta-Analysis (ENIGMA) performed a 23-site study including 2140 individuals with substance use problems (one of five substances: alcohol, nicotine, cocaine, methamphetamine, or cannabis) and 1100 individuals who were not addicted to any of these substances (although criteria did permit some use of these substances). Consistent with the past literature, they found that substancedependent patients (regardless of the substance) had several smaller subcortical volumes, including the bilateral hippocampus/amygdala and right accumbens, and smaller cortical thickness in 17 regions, including the left caudal middle frontal gyrus (MFG) and precuneus, right isthmus of cingulate gyrus, and bilateral middle temporal gyrus.…”