Abstract
Background: Cannabis is increasingly perceived as a harmless drug by recreational users, yet chronic use may impact brain changes into adulthood. Repeated cannabis exposure has been associated with enduring synaptic changes in executive control and reward networks. It is important to determine whether there are brain functional alterations within these networks in individuals that do not seek treatment for chronic cannabis abuse. Methods: This longitudinal study compared resting-state functional connectivity changes in executive control and reward networks between 23 non-treatment-seeking young adults with cannabis use disorder (6 females; baseline age M = 19.3 ± 1.18) and 21 age-matched controls (10 females; baseline age M = 19.4 ± 0.65) to determine group differences in the temporal trajectories of resting-state functional connectivity across a 2-year span. Results: Results showed i) significant increases in resting-state functional connectivity between the caudal anterior cingulate cortex and precentral and parietal regions over time in the control group, but not in the cannabis use disorder group, and ii) sustained lower resting-state functional connectivity of anterior cingulate cortex seeds with frontal and thalamic regions in the cannabis use disorder group vs. the age-matched controls. Resting-state functional connectivity strength was correlated with cannabis use patterns in the cannabis use disorder sample. Conclusion: Longitudinal alterations in intrinsic functional organization of executive control networks found in non-treatment-seeking young adults with cannabis use disorder (when compared to age-matched controls) may impact regulatory control over substance use behavior. Current findings were limited to examining executive control and reward networks seeded in ACC and NAcc, respectively. Future studies with larger sample sizes and enough power are needed to conduct exploratory analyses examining rsFC of other networks beyond those within the scope of the current study.
Highlights
Cannabis is increasingly perceived as a harmless substance [1]
To determine how networks associated with specific executive control domains changed across time between groups, we examined resting functional connectivity (rsFC) of five functionally distinct anterior cingulate cortex (ACC, Figure 1) networks for which changes across time have been examined in healthy controls as well as in adolescents with cannabis use disorder (CUD) [17, 19]: caudal ACC [MNI (Montreal Neurological Institute) coordinates: x = ±5, y = 10, z = 47), dorsal ACC (x = ±5, y = 14, z = 42), rostral ACC (x = ±5, y = 34, z = 28), perigenual ACC (x = ±5, y = 47, z = 11), and subgenual ACC (x = ±5, y = 25, z = 10)
While another study has reported immediate detrimental effects of cannabis manifested as reductions in rsFC within the default mode network [52], the current study provides additional supportive evidence of persistent frontal rsFC disruptions in young adults with CUD
Summary
Cannabis is increasingly perceived as a harmless substance [1]. Nearly 52% of 18- to 25-year olds in the USA report lifetime cannabis use (NIDA, 2014), with increasing rates of use among young adults. Many are chronic users who do not feel the need to stop using or seek treatment Given these trends, it is important to investigate the impact of regular cannabis use on brain networks in young adults. Chronic cannabis use alters synaptic pruning in the endocannabinoid system [3], which is involved in mediating executive function and reward processing [4], adversely affecting cognition and behavior [5,6,7]. Chronic cannabis use during critical developmental stages may affect aspects of integrity within networks that play a crucial role in drug-seeking behavior, such as the executive and reward processing networks, through enduring neurochemical alterations [8, 9]. Cannabis is increasingly perceived as a harmless drug by recreational users, yet chronic use may impact brain changes into adulthood. It is important to determine whether there are brain functional alterations within these networks in individuals that do not seek treatment for chronic cannabis abuse
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