Optimised Transcranial Magnetic Stimulation (TMS) for Obsessive Compulsive Disorder (OCD)

Participants will complete an initial clinical and cognitive assessment at the Epworth Centre for Innovation in Mental Health, followed by a baseline imaging session at the Royal Melbourne Hospital. The imaging session will comprise of a resting-state fMRI (rfMRI) paradigm, a structural MR image (T1), a Diffusion Tensor Image (DTI) and a clinical scan. Participants will then be pseudo-randomly assigned to receive (i) optimised TMS (TMS to the right frontal pole (FP), supplementary motor area (SMA) and superior frontal gyrus (SFG)); (ii) non-optimised TMS (stimulation to the right FP alone) or (iii) placebo (sham) stimulation. The optimised condition targets multiple areas in the brain (rFP, SMA,SFG) believed to be involved in OCD symptomology. The non-optimised condition only targets the right FP. Pseudo randomisation will be used to ensure that participants across the three groups are match on age, gender, handedness, IQ and baseline symptom severity score. Within the week following the MRI scan, participants will begin a 3-week protocol of TMS called continuous theta burst stimulation (cTBS). cTBS will be provided as 3-pulse 50 - Hz bursts applied at 5 Hz (ie 50 Hz burst of 3 pulses delivered every 200 msec). The TMS intervention itself will go for between 40 seconds and approximately 2 minutes depending on the treatment condition. The TMS treatment will be administered by registered nurses. Participants will not be told which treatment group (optimal, non-optimal, sham) they have been assigned to, and all 3 conditions (2 active, 1 sham) will have a similar duration and dose to avoid unblinding.