White Matter Integrity Pre- and Post Marijuana and Alcohol Initiation in Adolescence

Joanna Jacobus,Susan Tapert,Sunita Bava,M Infante,Lindsay Squeglia

doi:10.3390/brainsci3010396

Joanna Jacobus, Susan Tapert + Show 3 more

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https://doi.org/10.3390/brainsci3010396

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Abstract

Characterizing the effects of alcohol and marijuana use on adolescent brain development is important for understanding potential alterations in neurodevelopment. Several cross sectional studies have identified group differences in white matter integrity after initiation of heavy alcohol and marijuana use, however none have explored white matter trajectories in adolescents pre- and post initiation of use, particularly for marijuana users. This study followed 16 adolescents with minimal alcohol and marijuana use at ages 16–18 over three years. At follow-up, teens were 19–22 years old; half of the participants initiated heavy alcohol use and half initiated heavy alcohol and marijuana use. Repeated-measures ANOVA revealed 20 clusters in association and projection fibers tracts (p < 0.01) in which a group by time interaction was found. Most consistently, white matter integrity (i.e., fractional anisotropy) decreased for those who initiated both heavy alcohol and marijuana use over the follow-up interval. No effect of time or change in white matter integrity was seen for those who initiated alcohol use only in the majority of clusters. In most regions, at the baseline time point, teens who would later initiate both alcohol and marijuana use demonstrated white matter integrity greater than or equal to teens that initiated alcohol use only. Findings suggest poorer tissue integrity associated with combined initiation of heavy alcohol and marijuana use in late adolescence. While pre-existing differences may also be related to likelihood of substance use, the present data suggest an effect on tissue integrity for these teens transitioning to combined alcohol and marijuana use in later adolescence.

Highlights

Alcohol and marijuana use are typically initiated during adolescence, with rates of lifetime use increasing significantly into young adulthood
Not significant (p > 0.05), marijuana initiators (MJ) reported more other drug use episodes compared to alcohol initiators (ALC)
While previous investigations in our laboratory have identified poorer white matter integrity in adolescent alcohol users compared to controls [17,36], and in some cases compared to those with marijuana use histories [40], this study is unique in that we identified a subset of teens at an initial time point with minimal use histories and evaluated them 3-years later, after initiation of either heavy alcohol use or heavy alcohol and marijuana use; previous work in our laboratory has predominately looked at between-group differences after initiation, as most teens enter the study and remain within their substance use patterns

Summary

Introduction

Alcohol and marijuana use are typically initiated during adolescence, with rates of lifetime use increasing significantly into young adulthood. Alcohol use increases from 30% to 70% between 8th and 12th grade, with 24% of high school seniors endorsing recent binge drinking (i.e., >5 drinks in a row in the last two weeks). While alcohol and marijuana are the most commonly used substances among adolescents, their potential effects on the developing brain are not well understood. Elucidating the unique and interactive effects of these substances on brain development is crucial, as significant neural maturation in both gray and white matter occurs during adolescence. The adolescent brain undergoes marked decreases in gray matter along with linear increases in white matter, purportedly associated with myelination and to some degree, regressive changes to axons and dendrites [2,3,4]. Any potential neurotoxic insults during this crucial maturation process could have long-lasting implications on cognitive development [9,10,11]

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