A Review of Magnetic Resonance Spectroscopy Studies in Marijuana using Adolescents and Adults

Abstract

Marijuana (MJ) remains the most widely used illicit drug of abuse, and accordingly, is associated with adverse effects on mental and physical health, and neurocognitive decline. Studies investigating the neurobiology of underlying MJ effects have demonstrated structural and functional alterations in brain areas that contain moderate to high concentrations of cannabinoid (CB1) receptors and that are implicated in MJ-related cognitive decrements. Proton magnetic resonance spectroscopy (¹H MRS), a non-invasive imaging technique used to assess neurochemistry, has been widely applied to probe a variety of substance-abusing populations. To date, however, there is a relative paucity of MRS published studies characterizing changes in neurometabolite concentrations in MJ users. Thus, the current review provides a summary of data from the eight existing MRS studies of MJ use in adolescents and adults, as well as interpretations and implications of study findings. Future MRS studies that address additional factors such as sex differences, onset and duration of use, abstinence and age, are warranted, and would lead to a more thorough characterization of potential neurochemical correlates of chronic MJ use, which would fill critical gaps in the existing literature.

Keywords: Adolescence; Adulthood; Cannabis; Magnetic resonance spectroscopic imaging; Magnetic resonance spectroscopy; Marijuana; Neurochemistry.

Figure 1

Sample Single Voxel Thalamic ¹H Spectrum. Axial anatomical image illustrating the placement of a single voxel (2 × 2 × 3cm) in the right thalamus of a healthy subject acquired at 4.0 Tesla using 2D-JPRESS, and the associated ¹H spectrum (below). Abbreviations: tCr (Cr + PCr), total creatine; Glx, glutamine/glutamine/GABA complex; ml, myo-inositol; tCho, total choline; Glu, glutamate; NAA, N-acetylaspartate.