Impulsive decision-making and gambling severity: The influence of γ-amino-butyric acid (GABA) and glutamate-glutamine (Glx).

•Gambling severity correlates negatively with Glx in the dACC and occipital cortex.•dACC, dlPFC and occipital metabolites are tuned to reward magnitudes of discounting.•Discounting of small and medium rewards is negatively correlated with dACC GABA+.•Discounting of large rewards is negatively associated with dlPFC GABA+/Glx ratios.•In GD, discounting of large rewards is negatively correlated with occipital GABA+.