Number of datasets included in final analysis, quantitative quality metrics and voxel tissue fractions. HERMES data quality for GABA+ and GSH subspectra was assessed by SNR, linewidth and fit error. PRESS data quality assessed using the tNAA signal for SNR, linewidth and CRLBs. Data quality and voxel tissue composition did not differ significantly between groups with the exception of ACC GABA+ SNR (t(49) = 2.21, p = 0.032) which was higher in PPCS participants than controls. SNR: signal-to-noise ratio. fGM/fWM/fCSF are the voxel fractions of GM, WM and CSF.