Brain-Oscillation Synchronized Stimulation of the DMPFC

Inclusion Criteria: 1. Are 18-65 years old; 2. Have OCD as a primary disorder, confirmed by a Mini-International Neuropsychiatric Interview (MINI) diagnosis of OCD, with treatment resistance defined as a failure of at least one course of cognitive-behavioural therapy or a single trial of an SSRI; 3. Does not meet criteria for substance use disorder as determined by the MINI (with the exception of nicotine and caffeine); 4. Have a Y-BOCS score \>20; 5. Are fluent in the English language (spoken, written, reading); 6. Have had no increase or initiation of any psychotropic medication in the 4 weeks prior to screening; 7. Must be deemed to have capacity to provide informed consent; 8. Must sign and date the informed consent form; 9. Stated willingness to comply with all study procedures. Exclusion Criteria: 1. Have any contraindications to TMS as determined by the Transcranial Magnetic Stimulation Adult Safety Screen (TASS) questionnaire; 2. Have a history of a medical or neurological disorder that affects the central nervous system (e.g., traumatic brain injury, stroke, Parkinson's disease); 3. Are pregnant or breast feeding. TMS is not unsafe in pregnancy and therefore the study team is not requiring a pregnancy test prior to entry. If participants become pregnant during the study they will not be excluded. The study team is not including people who are currently aware of being pregnant as OCD can be affected during the later stages of pregnancy and therefore is a potential confound; 4. Have a history of seizures; 5. Have any metal implants or dentures; 6. Have a serious or unstable medical condition requiring immediate investigation or treatment (e.g., severe or recent cardiac disease); 7. Have a cardiac pacemaker, cochlear implants, implanted electronic devices, non-electronic metallic implants, or other contraindications for rTMS; 8. Take more than 2mg of lorazepam or equivalent benzodiazepine, or any anticonvulsant medication; 9. Fulfill criteria for Alcohol Use Disorder.