Prediction of adolescent substance use by individual differences in GABA and glutamate levels in the lateral prefrontal cortex: A preliminary exploration

Parikh, Ruja

Undergraduate Honors Thesis

Prediction of adolescent substance use by individual differences in GABA and glutamate levels in the lateral prefrontal cortex: A preliminary exploration Pubblico Deposited

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Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/8s45qb03g

Abstract

Adolescence is a period of time associated with lower levels of impulse control and is often the time during which youth begin to engage in substance use. Prior research has found that higher levels of impulsivity are associated with increased adolescent substance use. The brain structure responsible for impulse control, the prefrontal cortex (PFC), is underdeveloped in adolescents, which may help to explain increased levels of impulsivity observed during adolescence. As such, research has been conducted on the neural correlates of impulsivity in the PFC, including magnetic resonance spectroscopy (MRS) studies that measure levels of relevant neurotransmitters in relation to levels of impulsivity. However, the majority of this research has been focused on neurotransmitter levels in the medial PFC in adult populations – no previous studies have assessed the relationship between lateral PFC neurotransmitter levels and substance use in adolescents. This exploratory study examines whether individual differences in lateral PFC neurotransmitters γ-aminobutyric acid (GABA) and glutamate can significantly predict the age of onset and frequency of alcohol use in a nonclinical adolescent population. MRS was used to measure proxy values for GABA (GABA+) and glutamate (Glx; glutamate + glutamine) levels in the lateral PFC, and data on disinhibition and substance use were collected via self-report questionnaires. Results showed that higher levels of impulsivity were associated with earlier and more frequent substance use, as predicted per extensive prior literature. While the hypothesized relationship with GABA+ was not observed, higher Glx levels were associated with earlier onset of substance use while accounting for the joint relationships between both Glx and substance use with impulsivity. As a result, we concluded that the relationship between excitatory-inhibitory signaling in the lPFC and impulsivity levels is likely different in the developing adolescent brain than in adults, and future research in this area will help to expand upon the findings of this preliminary study.

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