Altered Frontal Cortical Volume and Decision Making in Adolescent Cannabis Users

Deborah A. Yurgelun-Todd,John C. Churchwell,Melissa Lopez-Larson

doi:10.3389/fpsyg.2010.00225

Abstract

Anticipating future outcomes is central to decision making and a failure to consider long-term consequences may lead to impulsive choices. Adolescence is a vulnerable period during which underdeveloped prefrontal cortical systems may contribute to poor judgment, impulsive choices, and substance abuse. Conversely, substance abuse during this period may alter neural systems involved in decision making and lead to greater impulsivity. Although a broad neural network which supports decision making undergoes extensive change during adolescent development, one region that may be critical is the medial prefrontal cortex. Altered functional integrity of this region may be specifically related to reward perception, substance abuse, and dependence. In the present investigation, we acquired structural magnetic resonance images (MRI), using a 3T Siemens Trio scanner, from 18 cannabis abusing adolescents (CA; 2 female and 16 male subjects; mean age, 17.7 years; range 16–19 years), and 18 healthy controls (HC; 6 female and 12 male subjects; mean age, 17.2 years; range 16–19 years). In order to measure medial orbital prefrontal cortex (moPFC) morphology related to substance abuse and impulsivity, semi-automated cortical reconstruction and volumetric segmentation of MRIs was performed with FreeSurfer. Impulsivity was evaluated with the Barratt Impulsiveness Scale (BIS). Our results indicate that cannabis abusing adolescents have decreased right moPFC volume compared to controls, p = 0.01, d = 0.92, CI0.95 = 0.21, 1.59. Cannabis abusing adolescents also show decreased future orientation, as indexed by the BIS non-planning subscale, when compared to controls, p = 0.01, d = 0.89, CI0.95 = 0.23, 1.55. Moreover, total moPFC volume was positively correlated with age of first use r (18) = 0.49, p < 0.03, suggesting that alterations in this region may be related to initiation of cannabis use or that early initiation may lead to reduced moPFC volume.

Highlights

Adolescence is a time during which a variety of factors may converge to increase the likelihood of substance use initiation, abuse, and dependence (Schepis et al, 2008)
Previous research indicates that early initiation of cannabis use is associated with reduced frontal cortical gray matter (Wilson et al, 2000) and that right medial orbital prefrontal cortex (moPFC) volume is negatively correlated with non-planning impulsivity (Matsuo et al, 2009)
While there were no significant correlations between right moPFC volume and several measures of cannabis use, total moPFC volume was positively associated with age of first use

Summary

Introduction

Adolescence is a time during which a variety of factors may converge to increase the likelihood of substance use initiation, abuse, and dependence (Schepis et al, 2008). Preclinical models have provided further evidence that chronic or escalating doses of delta-9-tetrahydrocannabinol produce alterations in prefrontal and nucleus accumbens dendritic morphology 30 days following treatment (Kolb et al, 2006) and this cellular reorganization may be related to disruptions in the function of these structures which are normally involved in reward representation and goal-directed behavior (Robinson and Kolb, 2004; Kalivas and Volkow, 2005) In accordance with this view, animal models have shown that brain reward systems become hypersensitive to drugs of abuse such as heroin and cocaine following adolescent cannabis exposure (Ellgren et al, 2007; Higuera-Matas et al, 2008). These studies indicate that the transition from childhood to adulthood involves a critical window during which cannabis use can impact normal remodeling of the prefrontal cortex (Egerton et al, 2006; Crews et al, 2007) and possibly alter the incentive salience of other drugs of abuse (Robinson and Berridge, 1993)

Methods

Results

Conclusion