Cortical thinness and volume differences associated with marijuana abuse in emerging adults

Abstract

Background The prevalence of marijuana (MJ) use among youth and its legalization for medical or recreational use has intensified public health endeavors of understanding MJ effects on brain structure and function. Studies indicate that MJ use is related to impaired cognitive performance, and altered functional brain activation and chemistry in adolescents and adults, but MJ effects on brain morphology in emerging adults are less understood. Methods 15 MJ users (age 21.8±3.6, 2 females) and 15 non-using (NU) participants (age 22.3±3.5, 2 females) were included, demographically matched on age, education and alcohol use. High-resolution structural MR images were acquired at 3 Tesla. Cortical thickness (CT) and volumetric analyses were performed using Freesurfer. A priori regions of interest (ROI) included orbitofrontal and cingulate cortices, amygdala, hippocampus and thalamus. Results Whole brain CT analysis did not find significant group differences in a priori ROIs but revealed MJ users had significantly less CT (i.e., thinness) in right fusiform gyrus (rFG) compared to NU (p<0.05). Thalamic volume was significantly smaller in MJ users compared to NU (right, p=0.05; left, p=0.01) and associated with greater non-planning (p<0.01) and overall impulsivity (p=0.04). There were no other group volume differences. Conclusions RFG cortical thinness and smaller thalamic volume in emerging adults is associated with MJ abuse. Furthermore, smaller thalamic volume associated with greater impulsivity contributes to growing evidence that the thalamus is neurobiologically perturbed by MJ use. Collectively, altered thalamic and rFG structural integrity may interfere with their known roles in regulating visuoperceptual and object information processing.

Sex differences in the interacting roles of impulsivity and positive alcohol expectancy in problem drinking: A structural brain imaging study

“…For instance, GMVs of brain regions including the thalamus mediated the effects of early life adversities on antisocial behavior (Mackey et al, 2016). Thalamic volume was significantly smaller in marijuana users compared to non-users and associated with greater non-planning and overall impulsivity (Mashhoon et al, 2015). In patients with psychotic disorders suicidal behavior was associated with reduced GMV in cortical and subcortical structures including the left thalamus (Giakoumatos et al, 2013).…”

The association of prenatal cocaine exposure, externalizing behavior and adolescent substance use

“…Interestingly, the difference in marijuana use by teens with PCE was largely driven by a greater number of males compared to girls with PCE. Given findings indicating that marijuana use among teens increases risk for psychosis (Green et al, 2016), poorer visual selective attention (Nicholls et al, 2015), lower academic achievement (Arria et al, 2015; Bechtold et al, 2016), and reduction in cortical thickness (Mashhoon et al, 2015), males with PCE could be at increased risk for negative effects of marijuana use. However, additional studies considering use quantity, frequency and/or marijuana use disorder symptoms would provide important clarifying information.…”

Cannabis Use in Youth is Associated with Limited Alterations in Brain Structure

“…While three studies have found larger volumes of cerebellar structures in adolescent frequent cannabis users [13,21,22], three also report equivocal findings or decreases in cerebellar volumes [17,23,24]. Frequent cannabis users have also been shown to have thinner prefrontal cortex [15,25], although several studies have not replicated these findings [14,26,27]. Finally, inconsistent results are apparent in amygdala, striatum, and cingulate cortex [10,13,15], despite their high density of CB1 receptors.…”

“…Several studies have reported associations between frequent cannabis use in adolescents and young adults and reductions in hippocampal volumes [10][11][12]. However, other studies do not replicate these reductions [13][14][15][16][17], including one longitudinal study [18]. Similarly, orbitofrontal cortex volumes have been examined, with mixed results [19,20].…”