Altered brain tissue composition in heavy marijuana users

Intramural Research Program, Neuroimaging Research Branch, National Institute on Drug Abuse, NIH/DHHS, 5500 Nathan Shock Drive, Baltimore, MD 21224-6823, USA.
Drug and Alcohol Dependence (Impact Factor: 3.42). 02/2005; 77(1):23-30. DOI: 10.1016/j.drugalcdep.2004.06.011
Source: PubMed


Marijuana is the most widely used illicit substance in the United States; however, previous imaging studies have not detected altered brain structure in marijuana users compared to non-users. Voxel-based morphometry was used to investigate possible differences in brain tissue composition in a group of 11 heavy marijuana users and a group of 8 non-users. All participants were male. Statistical comparisons were made at the voxel level on T1-weighted magnetic resonance images to determine differences in gray matter and white matter tissue density. Compared to non-users, marijuana users had lower gray matter density in a cluster of voxels in the right parahippocampal gyrus (P = 0.0001), and greater density bilaterally near the precentral gyrus and the right thalamus (P < 0.04). Marijuana users also had lower white matter density in the left parietal lobe (P = 0.03), and higher density around the parahippocampal and fusiform gyri on the left side compared to non-users (P < 0.002). Longer duration of marijuana use (in years) was significantly correlated with higher white matter tissue density in the left precentral gyrus (P = 0.045). Our preliminary results suggest evidence of possible structural differences in the brain of heavy marijuana users, and localize regions for further investigation of the effects of marijuana in the brain.

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    • "Based on evidence from observational studies, cannabis use has been linked to a number of effects on cognition and behaviour (Ranganathan & D'Souza, 2006; Solowij & Pesa, 2010), with memory being one of the most robustly replicated cognitive functions which has been reported to be impaired following chronic (non-acute) cannabis use (Grant et al. 2003; Fletcher & Honey, 2006; Solowij & Battisti, 2008; Solowij & Pesa, 2010; Schoeler & Bhattacharyya, 2013). Meta-analyses of observational studies comparing cannabis-using subjects with nonusing subjects have reported small (Grant et al. 2003) to medium-sized effects (Schreiner & Dunn, 2012) of cannabis on verbal memory performance, consistent with evidence that regular cannabis use affects the structure (Matochik et al. 2005; Yucel et al. 2008) and function (Kanayama et al. 2004; Sneider et al. 2008) of brain regions involved in memory processing. As discussed by Solowij & Battisti (2008), accumulating evidence suggests that the magnitude and persistence of cognitive impairment associated with cannabis use depends on various parameters such as age of onset (Pope et al. 2003; Gruber et al. 2012), dose (Bolla et al. 2002), frequency (Jager et al. 2006; Tait et al. 2011), and duration of cannabis use (Meier et al. 2012) as well as the period of abstinence from cannabis (Pope * Address for correspondence: S. "
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    ABSTRACT: Background: Effect of cannabis use on memory function is a contentious issue, with effects being different in healthy individuals and patients with psychosis. Method: Employing a meta-analytic approach we investigated the effects of cannabis use on memory function in patients with psychosis and healthy individuals, and the effect of diagnosis, memory dimension and moderating factors. A total of 88 studies were identified through a systematic literature search, investigating healthy (n = 7697) and psychotic (n = 3261) individuals. Standardized mean differences between the cannabis user and non-user groups on memory tasks were estimated using random-effects models and the effect-size statistic Cohen's d. Effects of potential moderating factors were tested using mixed-effects models and subgroup analyses. Results: We found that cannabis use was associated with significantly (p ⩽ 0.05) impaired global (d = 0.27) and prospective memory (d = 0.61), verbal immediate (d = 0.40) and delayed (d = 0.36) recall as well as visual recognition (d = 0.41) in healthy individuals, but a better global memory (d = -0.11), visual immediate recall (d = -0.73) and recognition (d = -0.42) in patients. Lower depression scores and younger age appeared to attenuate the effects of cannabis on memory. Cannabis-using patients had lower levels of depression and were younger compared with non-using patients, whilst healthy cannabis-users had higher depression scores than age-matched non-users. Longer duration of abstinence from cannabis reduced the effects on memory in healthy and patient users. Conclusions: These results suggest that cannabis use is associated with a significant domain-specific impairment in memory in healthy individuals but not in cannabis-using patients, suggesting that they may represent a less developmentally impaired subgroup of psychotic patients.
    Psychological Medicine 09/2015; DOI:10.1017/S0033291715001646 · 5.94 Impact Factor
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    • "Given the sub-optimal functional response of these a priori regions in MJ users during cognitive task performance, it is possible that surface-based cortical thickness analyses will reveal corresponding structural changes, with lower cortical thickness related to MJ use in these regions. Hippocampus, amygdala and thalamus, regions demonstrating high CB1 receptor distribution (Herkenham et al., 1991), also were selected for volumetric analysis based on evidence that MJ users exhibit functional and neurochemical alterations in these regions related to marijuana use (Ashtari et al., 2011; Bolla et al., 2005; Cousijn et al., 2012; Demirakca et al., 2011; Gilman et al., 2014; Glass et al., 1997; Hester et al., 2009; Mashhoon et al., 2013; Matochik et al., 2005; Schacht et al., 2012; Sneider et al., 2013a,b; Yucel et al., 2008). Clinical measures of mood and impulsivity were examined relative to cortical thickness and brain volume to further probe potential links with neurobiological consequences of marijuana use. "
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    ABSTRACT: The prevalence of marijuana (MJ) use among youth and its legalization for medical or recreational use has intensified public health endeavors of understanding MJ effects on brain structure and function. Studies indicate that MJ use is related to impaired cognitive performance, and altered functional brain activation and chemistry in adolescents and adults, but MJ effects on brain morphology in emerging adults are less understood. Fifteen MJ users (age 21.8±3.6, 2 females) and 15 non-user (NU) participants (age 22.3±3.5, 2 females) were included, demographically matched on age, education and alcohol use. High-resolution structural MR images were acquired at 3Tesla. Cortical thickness (CT) and volumetric analyses were performed using Freesurfer. A priori regions of interest (ROI) included orbitofrontal and cingulate cortices, amygdala, hippocampus and thalamus. Whole brain CT analysis did not result in significant group differences in a priori ROIs but revealed MJ users had significantly less CT (i.e., thinness) in right fusiform gyrus (rFG) compared to NU (p<0.05). Thalamic volume was significantly smaller in MJ users compared to NU (right, p=0.05; left, p=0.01) and associated with greater non-planning (p<0.01) and overall impulsivity (p=0.04). There were no other group differences. RFG cortical thinness and smaller thalamic volume in emerging adults is associated with MJ abuse. Furthermore, smaller thalamic volume associated with greater impulsivity contributes to growing evidence that the thalamus is neurobiologically perturbed by MJ use. Collectively, altered thalamic and rFG structural integrity may interfere with their known roles in regulating visuoperceptual and object information processing. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
    Drug and Alcohol Dependence 06/2015; in press. DOI:10.1016/j.drugalcdep.2015.06.016 · 3.42 Impact Factor
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    • "While findings for many regions were mixed, there is growing evidence that adult users demonstrate reductions in hippocampal volumes (Fig. 1), with two studies reporting an association between volume reduction in the hippocampus and cumulative lifetime cannabis exposure (Yücel et al., 2006; Yücel et al., 2008). Parahippocampal alterations have also been reported amongst high frequency users (but were not found in samples that had less exposure to cannabis; Matochik et al., 2005; Tzilos et al., 2005; Jager et al., 2007). In addition, a more recent study examining hippocampal shape alterations in cannabis users with and without schizophrenia found that abnormalities in hippocampal morphology (specifically, deflations across the hippocampus with an anterior predisposition ) were associated with cannabis use patterns as well as symptoms of psychosis (Solowij et al., 2013). "
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    ABSTRACT: Heavy cannabis use has been frequently associated with increased rates of mental illness and cognitive impairment, particularly amongst adolescent users. However, the neurobiological processes that underlie these associations are still not well understood. In this review, we discuss the findings of studies examining the acute and chronic effects of cannabis use on the brain, with a particular focus on the impact of commencing use during adolescence. Accumulating evidence from both animal and human studies suggests that regular heavy use during this period is associated with more severe and persistent negative outcomes than use during adulthood, suggesting that the adolescent brain may be particularly vulnerable to the effects of cannabis exposure. As the endocannabinoid system plays an important role in brain development, it is plausible that prolonged use during adolescence results in a disruption in the normative neuromaturational processes that occur during this period. We identify synaptic pruning and white matter development as two processes that may be adversely impacted by cannabis exposure during adolescence. Potentially, alterations in these processes may underlie the cognitive and emotional deficits that have been associated with regular use commencing during adolescence.
    Pharmacology [?] Therapeutics 11/2014; 148. DOI:10.1016/j.pharmthera.2014.11.009 · 9.72 Impact Factor
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