Region-specific glutamate changes in patients with unipolar depression.

The present study aimed to investigate glutamate concentrations in patients with unipolar depression in the midcingulate cortex (MCC) as compared to the left dorsolateral prefrontal cortex (DLPFC). We hypothesized a dissociation of glutamate levels with unchanged levels in DLPFC and abnormally changed levels in MCC as well as differential effects of antidepressant pharmacotherapy. Glutamate was determined using magnetic resonance spectroscopy at 3 T in DLPFC and MCC in fourteen depressed patients and matched healthy volunteers. A follow-up measurement was performed after 4 weeks of antidepressant treatment. The main finding is a region-specific pattern of glutamate concentrations with increased MCC glutamate concentrations and no significant differences in DLPFC glutamate concentrations in unipolar depressive patients compared to healthy controls. Response and non-response to antidepressant pharmacotherapy were predicted by high glutamate at baseline in DLPFC and MCC, respectively. In addition, treatment responders showed a further increase in DLPFC glutamate levels after successful antidepressant treatment. Findings indicate altered region-specific glutamate concentrations in DLPFC and MCC that are predictive of response and non-response, respectively, to antidepressant pharmacotherapy. These findings might serve as a starting point for future studies in which the value of this metabolite pattern for treatment response prediction should be investigated.