Pharmacologic Augmentation of TMS for Depression With D-serine

Inclusion Criteria: * Clinical diagnosis of MDD * English-speaking * Adults aged 18-80 * Must be able to swallow capsules Relative contraindications/possible exclusion criteria: * Containing any implanted metal or devices * Current or previous seizure history * Active substance use that may significantly alter the seizure threshold Any further safety clearances, and outpatient consultation opinions that are necessitated based on the answers to the screening will be obtained prior to moving forward with the study, as an already established practice within the clinic practice. In addition, any relative contraindications will be further reviewed according to Rossi et al.'s most updated safety guidelines for TMS. Exclusion Criteria: * Patients with pre-existing renal disease * Known allergy to D-serine, or with * Patients taking medications with known drug-drug interactions * Children * Pregnant or breast-feeding women The investigators will not include children because prior safety and dosing studies excluded children. Although considered safe for TMS, the investigators will not include pregnant or breast-feeding women on the basis of unknown safety profile of exogenous D-serine for these patients.