Altered cerebral blood flow and neurocognitive correlates in adolescent cannabis users (original) (raw)
Related papers
Effects of Smoking Marijuana on Brain Perfusion and Cognition
Neuropsychopharmacology, 2002
The effects of smoking marijuana on regional cerebral blood flow (rCBF) and cognitive performance were assessed in 12 recreational users in a double-blinded, placebo-controlled study. PET with [ 15 Oxygen]-labeled water ([ 15 O]H 2 O) was used to measure rCBF before and after smoking of marijuana and placebo cigarettes, as subjects repeatedly performed an auditory attention task.
Effects of frequent marijuana use on memory-related regional cerebral blood flow
Pharmacology Biochemistry and Behavior, 2002
It is uncertain whether frequent marijuana use adversely affects human brain function. Using positron emission tomography (PET), memory-related regional cerebral blood flow was compared in frequent marijuana users and nonusing control subjects after 26+ h of monitored abstention. Memory-related blood flow in marijuana users, relative to control subjects, showed decreases in prefrontal cortex, increases in memory-relevant regions of cerebellum, and altered lateralization in hippocampus. Marijuana users differed most in brain activity related to episodic memory encoding. In learning a word list to criterion over multiple trials, marijuana users, relative to control subjects, required means of 2.7 more presentations during initial learning and 3.1 more presentations during subsequent relearning. In single-trial recall, marijuana users appeared to rely more on short-term memory, recalling 23% more than control subjects from the end of a list, but 19% less from the middle. These findings indicate altered memory-related brain function in marijuana users.
Effects of Cannabis on the Adolescent Brain
This article reviews neuroimaging, neurocognitive, and preclinical findings on the effects of cannabis on the adolescent brain. Marijuana is the second most widely used intoxicant in adolescence, and teens who engage in heavy marijuana use often show disadvantages in neurocognitive performance, macrostructural and microstructural brain development, and alterations in brain functioning. It remains unclear whether such disadvantages reflect pre-existing differences that lead to increased substances use and further changes in brain architecture and behavioral outcomes. Future work should focus on prospective investigations to help disentangle dose-dependent effects from pre-existing effects, and to better understand the interactive relationships with other commonly abused substances (e.g., alcohol) to better understand the role of regular cannabis use on neurodevelopmental trajectories.
Altered regional blood volume in chronic cannabis smokers
Experimental and Clinical Psychopharmacology, 2006
The quantitative measurement of cerebral perfusion is crucial for the study of both normal and impaired human brain function. Although cannabis is the most commonly abused illicit substance in the United States, its effects on cerebral blood volume (CBV) have not been fully examined. The objective of the present study was to examine differences in relative regional blood volume in focal regions of interest-including the frontal lobe, the temporal lobe, and the cerebellum-during a period of supervised abstinence from cannabis. Dynamic susceptibility contrast MRI data were collected on 12 current, long-term daily cannabis users between 6 and 36 hr after the subjects' last reported cannabis use. Resting-state CBV images were also acquired in 17 healthy comparison subjects. Data were acquired in the axial plane with a 1.5-Tesla GE Signa scanner following a bolus of gadolinium contrast agent. Cannabis users demonstrated significantly increased blood volumes in the right frontal area (p Ͻ .05), in the left temporal area (p Ͻ .005), and in the cerebellum (p Ͻ .005) relative to comparison subjects. Among the cannabis users, there were no significant correlations between regional blood volumes and either total lifetime episodes of smoking or urinary tetrahydrocannabinol concentrations. These findings have important implications for understanding the effects of chronic heavy cannabis use on brain function. It would be of interest to extend the investigation beyond 6-36 hr of abstinence from cannabis to determine whether increased CBV values persist for several weeks or eventually normalize.
SUMMARY Comparative study based on 565 school adolescents coming from four schools in the metropolitan area of Santiago, Chile. All were interviewed in order to select a sample that was stratified by sex, class and condition of users or non users. The variables of intelligence quotient and socioeconomic status were maintained constant. Two groups were made: 40 marijuana-only users and 40 non users. We compared the results obtained in both groups in the neuropsychologi-cal tests while the neuroSPECT studies of users were compared against a normal database for the same age group. Adolescent marijuana users demonstrate less cognitive capacity related to the process of learning such as attention, concentration , ranking, visuo-spatial integration, immediate retention and visual memory. The differences between both groups are statistically significant. The findings of neuroSPECT show subgenual bilateral hypoper-fusion, more marked on the left side (Brodmann's area 25), frontal bilateral hypoperfusion (Brodmann's areas 10 and 32), front cingu-late gyrus hypoperfusion (Brodmann's area 24) and hypoperfusion of Brodmann's area 36 that projects over the hippocampus. Students that were only-marijuana users demonstrate coincident abnormal findings of neuroimages and neuropsychological tests in brain learning-related areas and also significant differences between users with non users in the neuropsychological tests. RESUMEN Estudio comparativo basado en 565 escolares adolescentes pertene-cientes a cuatro colegios de Santiago, Chile. Fueron encuestados todos para seleccionar una muestra estratificada por sexo, curso y condición de consumidores o no consumidores, manteniendo constante las variables coeficiente intelectual y nivel socioeconómico. Se conforman dos grupos: 40 consumidores exclusivos de marihuana y 40 no consumido-res. Se comparan los resultados obtenidos en ambos grupos en los Test Neuropsicológios y del NeuroSPECT de consumidores con una base de datos considerados normales para el mismo grupo etario. Los adolescentes consumidores de marihuana evidencian me-nores habilidades cognitivas asociadas al proceso de aprendizaje, tales como atención, concentración, jerarquización, integración viso-espacial, retención inmediata y memoria visual. Las diferencias entre ambos grupos son estadísticamente significativas. Los hallazgos del NeuroSPECT muestran hipoperfusión subge-nual bilateral, más marcada en el hemisferio izquierdo (área 25 de Brodmann), hipoperfusión frontal bilateral (areas 10 y 32 de Brod-mann), hipoperfusión del gyrus cingulado anterior (área 24 de Brod-mann) e hipoperfusión del área 36 de Brodmann que proyecta sobre el hipocampo. Los estudiantes consumidores exclusivamente de marihuana muestran compromiso coincidente en neuroimágenes y test neuropsi-cológicos en áreas del cerebro relacionadas con el aprendizaje y se diferencian significativamente de los no-consumidores en las pruebas neuropsicológicas.
Daily marijuana use is not associated with brain morphometric measures in adolescents or adults
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2015
Recent research has suggested that marijuana use is associated with volumetric and shape differences in subcortical structures, including the nucleus accumbens and amygdala, in a dose-dependent fashion. Replication of such results in well controlled studies is essential to clarify the effects of marijuana. To that end, this retrospective study examined brain morphology in a sample of adult daily marijuana users (n = 29) versus nonusers (n = 29) and a sample of adolescent daily users (n = 50) versus nonusers (n = 50). Groups were matched on a critical confounding variable, alcohol use, to a far greater degree than in previously published studies. We acquired high-resolution MRI scans, and investigated group differences in gray matter using voxel-based morphometry, surface-based morphometry, and shape analysis in structures suggested to be associated with marijuana use, as follows: the nucleus accumbens, amygdala, hippocampus, and cerebellum. No statistically significant differences w...
Long-term effects of marijuana use on the brain
Proceedings of the National Academy of Sciences of the United States of America, 2014
Questions surrounding the effects of chronic marijuana use on brain structure continue to increase. To date, however, findings remain inconclusive. In this comprehensive study that aimed to characterize brain alterations associated with chronic marijuana use, we measured gray matter (GM) volume via structural MRI across the whole brain by using voxel-based morphology, synchrony among abnormal GM regions during resting state via functional connectivity MRI, and white matter integrity (i.e., structural connectivity) between the abnormal GM regions via diffusion tensor imaging in 48 marijuana users and 62 age- and sex-matched nonusing controls. The results showed that compared with controls, marijuana users had significantly less bilateral orbitofrontal gyri volume, higher functional connectivity in the orbitofrontal cortex (OFC) network, and higher structural connectivity in tracts that innervate the OFC (forceps minor) as measured by fractional anisotropy (FA). Increased OFC function...
The Influence of Marijuana Use on Neurocognitive Functioning in Adolescents
Current Drug Abuse Reviewse, 2008
Marijuana use is common in adolescence, yet neural consequences have not been well delineated. This review seeks to ascertain whether heavy marijuana use in adolescence is associated with persistent neurocognitive abnormalities, and whether adolescents are more vulnerable to the impact of chronic marijuana use than adults. Among heavy marijuana using adults, neurocognitive deficits are apparent for several days following use, but may disappear after one month of abstinence. Studies of adolescent heavy users have identified impairments in learning and working memory up to six weeks after cessation, suggesting persisting effects, yet raise the possibility that abnormalities may remit with a longer duration of abstinence. Given ongoing neuromaturation during youth, adolescents may be more vulnerable to potential consequences of marijuana use than adults. This is supported by rodent models, which show greater memory impairments in animals exposed to cannabinoids as adolescents relative to those exposed as adults. Further, adult humans who initiated use in early adolescence show greater dysfunction than those who began use later. Together, these results suggest that adolescents are more vulnerable than adults to neurocognitive abnormalities associated with chronic heavy marijuana use; however, the impact of preexisting risk factors is unknown. Adolescents demonstrate persisting deficits related to heavy marijuana use for at least six weeks following discontinuation, particularly in the domains of learning, memory, and working memory. Further, adolescents appear more adversely affected by heavy use than adults. Longitudinal studies will help ascertain whether preexisting differences contribute to these abnormalities.