Worth the wait: effects of age of onset of marijuana use on white matter and impulsivity

Abstract

RationaleMarijuana (MJ) use continues to rise, and as the perceived risk of using MJ approaches an all-time historic low, initiation of MJ use is occurring at even younger ages. As adolescence is a critical period of neuromaturation, teens and emerging adults are at greater risk for experiencing the negative effects of MJ on the brain. In particular, MJ use has been shown to be associated with alterations in frontal white matter microstructure, which may be related to reports of increased levels of impulsivity in this population.ObjectivesThe aim of this study was to examine the relationship between age of onset of MJ use, white matter microstructure, and reported impulsivity in chronic, heavy MJ smokers.MethodsTwenty-five MJ smokers and 18 healthy controls underwent diffusion tensor imaging and completed the Barratt Impulsiveness Scale. MJ smokers were also divided into early onset (regular use prior to age 16) and late onset (age 16 or later) groups in order to clarify the impact of age of onset of MJ use on these variables.ResultsMJ smokers exhibited significantly reduced fractional anisotropy (FA) relative to controls, as well as higher levels of impulsivity. Earlier MJ onset was also associated with lower levels of FA. Interestingly, within the early onset group, higher impulsivity scores were correlated with lower FA, a relationship that was not observed in the late onset smokers.ConclusionsMJ use is associated with white matter development and reported impulsivity, particularly in early onset smokers.

Cannabinoids and Epilepsy

“…Long-term use of recreational cannabis in adolescents is associated with addiction (9 % overall but 17 % among adolescents) and impaired cognitive and academic performance [270][271][272][273][274]. Additionally, cannabis treatment in animal and human studies altered brain development (especially with use in early childhood) and structure [272,[275][276][277], creating long-lasting functional and structural brain abnormalities [277][278][279]. Early and/or heavy cannabis use is associated with neurochemical abnormalities on magnetic resonance spectroscopy [272], impaired maintenance of neuronal cytoskeleton dynamics [277], decreased white matter development or integrity [272,275,276], increased impulsivity [276], and abnormal activation patterns during cognitive tasks on functional magnetic resonance imaging [272,280].…”

“…Additionally, cannabis treatment in animal and human studies altered brain development (especially with use in early childhood) and structure [272,[275][276][277], creating long-lasting functional and structural brain abnormalities [277][278][279]. Early and/or heavy cannabis use is associated with neurochemical abnormalities on magnetic resonance spectroscopy [272], impaired maintenance of neuronal cytoskeleton dynamics [277], decreased white matter development or integrity [272,275,276], increased impulsivity [276], and abnormal activation patterns during cognitive tasks on functional magnetic resonance imaging [272,280]. In patients with multiple sclerosis, use of cannabis is associated with impaired cognition and activation patterns on functional magnetic resonance imaging [281].…”

UPPS-P model impulsivity and marijuana use behaviors in adolescents: A meta-analysis

“…These negative outcomes are more likely and problematic the earlier a person begins using marijuana Dévieux et al, 2002;Gruber et al, 2014). Adolescents make up the largest proportion of marijuana users and over 75% of people who begin using marijuana each year are aged 12-20 (NIDA, 2014).…”

“…Furthermore, adolescents that use marijuana are more likely to engage in other risk taking behaviors such as stealing, using weapons in acts of violence, having risky sex, and having accidental injuries (Brook et al, 1999;Castellanos-Ryan et al, 2013;Chassin et al, 2010;Churchwell et al, 2010;Crews et al, 2007;Dévieux et al, 2002). Using marijuana can stunt brain development, including development of socio-emotional areas (i.e., amygdala, ventral striatum, orbitofrontal cortex, medial prefrontal cortex, and superior temporal sulcus) and cognitive control (i.e., lateral prefrontal, lateral parietal, and anterior cingulate cortices) (e.g., Crews et al, 2007;Chassin et al, 2010;Gruber et al, 2014), leading to the more pronounced difficulties in adulthood (e.g., Hall, 2009;Hall and Degenhardt, 2009;Meier et al, 2012).…”

An MRI study of white matter tract integrity in regular cannabis users: effects of cannabis use and age

“…The current literature on white matter in cannabis users has generally focused on adolescents and young adults, utilising samples with a mean age less than 25 (DeLisi et al 2006;Arnone et al 2008;Gruber et al 2011;Gruber et al 2014;Shollenbarger et al 2015) or 20 (Ashtari et al 2009;Jacobus et al 2009;Bava et al 2010;Becker et al 2015), with only two studies utilising slightly older participants (mean 27 years of age, Rigucci et al 2015, and mean 28 years of age, Filbey et al 2014). While this focus may be justified by concerns regarding the critical brain development occurring during this period (Bossong and Niesink 2010), restriction to young samples may impose major limitations to understanding the impact of cannabis exposure on white matter given its prolonged developmental trajectory.…”