Theta-Burst Stimulation to Treat Depression

To join this study, you need to be an adult between 18 and 50 years old and have been diagnosed with Major Depressive Disorder. If you're currently taking antidepressant medication, it needs to have been at a steady dose for at least 4 weeks before you start the study. You also need to be right-handed or able to use both hands, and understand English well enough to follow instructions.

There are some reasons why you wouldn't be able to join. These include if you are younger than 18 or older than 50, or if you have certain other mental health conditions like bipolar disorder or a history of psychosis. We also can't include people who have a high risk of suicide.

For safety reasons, you can't take part if you have any metal implants in your body (like a pacemaker or certain dental work), have a history of seizures, or are pregnant. Also, if you're taking certain medications like antipsychotics or anti-epileptic drugs, or some sedatives, you might not be eligible, as these can affect how the brain stimulation works. However, if you're taking gabapentin or pregabalin for chronic pain and your dose has been steady for 4 weeks, you might still be able to join.

If you decide to take part, your commitment will involve about 5 study visits spread over 2 to 3 months. This is what you can expect:

* **Initial Check-up (Visit 1):** We'll do some tests to make sure you're suitable for the study. You'll also have a trial run of the brain stimulation, called a 'sham' session, which feels like the real thing but doesn't actually stimulate the brain, just to see how you tolerate it. * **Brain Scan and Randomisation (Visit 2):** You'll have an MRI brain scan. After this, you'll be randomly assigned to start with either the 'spaced' or 'compressed' iTBS treatment. * **Treatment Block 1 (Visits 3-5):** Over three separate sessions, you'll receive the first type of iTBS treatment you were assigned. Each session will include safety checks, the iTBS treatment, and measurements of your brain activity and mood. There will then be a break of at least two weeks. * **Treatment Block 2 (Visits 6-8):** After the break, you'll undergo three more sessions, but this time you'll receive the *other* type of iTBS treatment (the one you didn't receive first). Again, each session will involve safety checks, the iTBS treatment, brain activity measurements, and mood questionnaires.

Throughout the study, you'll continue any antidepressant medication you are already on, provided it's at a stable dose. We won't be asking you to change your medication unless your doctor advises it. The total time commitment for all visits and treatments will be roughly 2-3 months.