Long-term effects of marijuana use on the brain.
Francesca Filbey, Sina Aslan, Vince D Calhoun, Jeffrey S Spence, Eswar Damaraju, Arvind Caprihan, Judith Segall
Proceedings of the National Academy of Sciences November 25, 2014 DOI: 10.1073/pnas.1415297111 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Cross-sectional neuroimaging study Longitudinal Peer reviewed |
|---|---|
| Sample size | 110 |
| Population | 48 chronic marijuana users and 62 age- and sex-matched nonusing controls |
| Topics | Cannabis |
| Keywords | Diffusion tensor imaging Functional connectivity Orbitofrontal cortex Resting State FMRI |
| Key findings | Chronic marijuana users had less bilateral orbitofrontal gyri gray matter volume, higher orbitofrontal cortex functional connectivity, and higher fractional anisotropy in the forceps minor tract than nonusing controls. Greater OFC functional connectivity was associated with earlier age of onset, and fractional anisotropy showed a quadratic pattern, initially increasing with regular use and decreasing with protracted use, which the authors suggest may reflect neuroadaptive processes. |
Abstract
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 functional connectivity in marijuana users was associated with earlier age of onset. Lastly, a quadratic trend was observed suggesting that the FA of the forceps minor tract initially increased following regular marijuana use but decreased with protracted regular use. This pattern may indicate differential effects of initial and chronic marijuana use that may reflect complex neuroadaptive processes in response to marijuana use. Despite the observed age of onset effects, longitudinal studies are needed to determine causality of these effects.
Comparable studies
Other experimental studies on cannabis, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Smoked Cannabis' Psychomotor and Neurocognitive Effects in Occasional and Frequent Smokers Occasional (<2x/week) and frequent (≥4x/week) cannabis smokers | 2015 | Controlled within-subjects study | n = 25 |
| Dissociable effects of cannabis with and without cannabidiol on the human brain’s resting-state functional connectivity Healthy volunteers experienced with cannabis but not regular users | 2019 | Within-subjects experimental design | n = 17 |
| Which biological and self-report measures of cannabis use predict cannabis dependency and acute psychotic-like effects? Young cannabis users | 2018 | Observational study (naturalistic, within-subject counterbalanced design) | n = 410 |
| Cannabis Essential Oil: A Preliminary Study for the Evaluation of the Brain Effects Healthy volunteers | 2018 | Experimental study | n = 5 |
| Coming off cannabis: a cognitive and magnetic resonance imaging study in patients with multiple sclerosis Patients with multiple sclerosis who began using cannabis after disease onset, used it... | 2019 | Quasi-experimental study with odd-even allocation | n = 40 |
Citations in the library
Cited by 33
- The neuropsychopharmacology of cannabis: A review of human imaging studies Pharmacology & Therapeutics October 20, 2018
- Subcortical Local Functional Hyperconnectivity in Cannabis Dependence Biological Psychiatry: Cognitive Neuroscience and Neuroimaging November 23, 2017
- Reduced responsiveness of the reward system is associated with tolerance to cannabis impairment in chronic users Addiction Biology December 22, 2019
- Reduced responsiveness of the reward system underlies tolerance to cannabis impairment in chronic users bioRxiv (Cold Spring Harbor Laboratory) July 19, 2019
- Cannabis Perturbs Dynamic Brain States Biological Psychiatry October 21, 2025
and 28 more in the library
Cites 11
- Resting-State Functional Connectivity Reflects Structural Connectivity in the Default Mode Network Cerebral Cortex April 9, 2008
- Cannabis use is quantitatively associated with nucleus accumbens and amygdala abnormalities in young adult recreational users. Journal of Neuroscience April 16, 2014
- Altered resting-state connectivity in adolescent cannabis users. The American Journal of Drug and Alcohol Abuse November 2013
- Reversible and regionally selective downregulation of brain cannabinoid CB1 receptors in chronic daily cannabis smokers Molecular Psychiatry July 12, 2011
- Medial temporal structures and memory functions in adolescents with heavy cannabis use Journal of Psychiatric Research February 5, 2011
and 6 more in the library