Glutamate Probes in Adolescent Depression

This is a cross-sectional and longitudinal neurophysiology research study of 200 adolescent subjects in varying stages of major depressive disorder (MDD). The aims of this study are designed to gain an understanding of (1) the role of glutamate in the neurophysiology and pharmacologic treatment of child and adolescent MDD; (2) the role of gamma-aminobutyric acid (GABA) in the neurophysiology and pharmacologic treatment of child and adolescent MDD; (3) the trajectory of glutamatergic and GABAergic functioning in human development with MDD. Glutamate concentrations in the anterior cingulate cortex (ACC) and left dorsolateral prefrontal (L-DLPFC) cortex will be evaluated using proton magnetic resonance spectroscopy (MRS) at 3 Tesla (3T). Glutamatergic cortical excitability measures (with motor threshold and intracortical facilitation paradigms), and GABAergic cortical inhibitory measures (with cortical silent period and intracortical inhibition paradigms) will be studied using single and paired-pulse transcranial magnetic stimulation (TMS) paradigms.