Lorenzetti Valentina, Kowalczyk Magdalena, Duehlmeyer Leonie, Greenwood Lisa-Marie, Chye Yann, Yücel Murat, Whittle Sarah, Roberts Carl A
Neuroscience of Addiction and Mental Health Program, Healthy Brain and Mind Research Centre, School of Behavioural and Health Sciences, Faculty of Health Sciences, Australian Catholic University, Fitzroy, Australia.
Research School of Psychology, The Australian National University, Canberra, Australia.
Cannabis Cannabinoid Res. 2023 Feb;8(1):184-196. doi: 10.1089/can.2021.0099. Epub 2022 Apr 19.
Cannabis use has a high prevalence in young youth and is associated with poor psychosocial outcomes. Such outcomes have been ascribed to the impact of cannabis exposure on the developing brain. However, findings from individual studies of volumetry in youth cannabis users are equivocal. Our primary objective was to systematically review the evidence on brain volume differences between young cannabis users and nonusers aged 12-26 where profound neuromaturation occurs, accounting for the role of global brain volumes (GBVs). Our secondary objective was to systematically integrate the findings on the association between youth age and volumetry in youth cannabis users. Finally, we aimed to evaluate the quality of the evidence. A systematic search was run in three databases (PubMed, Scopus, and PsycINFO) and was reported using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We run meta-analyses (with and without controlling for GBV) of brain volume differences between young cannabis users and nonusers. We conducted metaregressions to explore the role of age on volumetric differences. Sixteen studies were included. The reviewed samples included 830 people with mean age 22.5 years (range 14-26 years). Of these, 386 were cannabis users (with cannabis use onset at 15-19 years) and 444 were controls. We found no detectable group differences in any of the GBVs (intracranium, total brain, total white matter, and total gray matter) and regional brain volumes (i.e., hippocampus, amygdala, orbitofrontal cortex, and total cerebellum). Age and cannabis use level did not predict (standardized mean) volume group differences in metaregression. We found little evidence of publication bias (Egger's test >0.1). Contrary to evidence in adult samples (or in samples mixing adults and youth), previous single studies in young cannabis users, and meta-analyses of brain function in young cannabis users, this early evidence suggests nonsignificant volume differences between young cannabis users and nonusers. While prolonged and long-term exposure to heavy cannabis use may be required to detect gross volume alterations, more studies in young cannabis users are needed to map in detail cannabis-related neuroanatomical changes.
大麻在青少年中使用极为普遍，且与不良的心理社会后果相关。此类后果被归因于接触大麻对发育中大脑的影响。然而，针对青少年大麻使用者脑容量测定的个别研究结果并不明确。我们的主要目标是系统回顾有关12至26岁青少年大麻使用者与非使用者之间脑容量差异的证据，这一年龄段会发生深刻的神经成熟过程，并考虑全脑容量（GBV）的作用。我们的次要目标是系统整合有关青少年大麻使用者年龄与脑容量测定之间关联的研究结果。最后，我们旨在评估证据的质量。在三个数据库（PubMed、Scopus和PsycINFO）中进行了系统检索，并按照系统评价和Meta分析的首选报告项目（PRISMA）指南进行报告。我们对青少年大麻使用者与非使用者之间的脑容量差异进行了Meta分析（包括控制和不控制GBV的情况）。我们进行了Meta回归分析，以探讨年龄对容量差异的作用。纳入了16项研究。所审查的样本包括830人，平均年龄22.5岁（范围为14至26岁）。其中，386人为大麻使用者（大麻使用起始年龄为15至19岁），444人为对照组。我们发现，在任何全脑容量（颅腔、全脑、全白质和全灰质）以及区域脑容量（即海马体、杏仁核、眶额皮质和小脑整体）方面，均未检测到组间差异。在Meta回归分析中，年龄和大麻使用水平并未预测（标准化均值）容量组差异。我们几乎没有发现发表偏倚的证据（Egger检验>0.1）。与成人样本（或成人与青少年混合样本）中的证据、之前针对青少年大麻使用者的个别研究以及青少年大麻使用者脑功能的Meta分析相反，这一早期证据表明，青少年大麻使用者与非使用者之间的容量差异不显著。虽然可能需要长期大量接触大麻才能检测到明显的容量改变，但仍需要更多针对青少年大麻使用者的研究来详细描绘与大麻相关的神经解剖学变化。
