Three adolescent groups from Cape Town, South Africa completed MRS scans as well as clinical measures including a drug use history. Subjects included (1) nine MA (age = 15.7 ¡À 1.37), (2) eight MA + MJ (age = 16.2 ¡À 1.16) using adolescents and (3) ten healthy controls (age = 16.8 ¡À 0.62). Single voxel spectra were acquired from midfrontal gray matter using a point-resolved spectroscopy sequence (PRESS). The MRS data were post-processed in the fully automated approach for quantitation of metabolite ratios to phosphocreatine plus creatine (PCr + Cr).
A significant reduction in frontal tNAA/PCr + Cr ratios was seen in the MA + MJ group compared to the healthy controls (p = 0.01, by 7.2 % ) and to the MA group (p = 0.04, by 6.9 % ). Significant relationships were also observed between decreased tNAA/PCr + Cr ratios and drug use history of MA or MJ (total cumulative lifetime dose, age of onset, and duration of MA and MJ exposure) only in the MA + MJ group (all p < 0.05).
These findings suggest that in adolescents, concomitant heavy MA + MJ use may contribute to altered brain metabolites in frontal gray matter. The significant associations between the abnormal tNAA/PCr + Cr ratios and the drug use history suggest that MA + MJ abuse may induce neurotoxicity in a dose-responsive manner in adolescent brain.