Model-based Defining of Subtypes of Depression and Optimal Treatment: an Integrated Techniques Module.

This study is using brain imaging and biological tests to identify specific subtypes of severe depression in order to match patients to the most effective treatment for their type. **You may be eligible if...** - You are between 18 and 65 years old - You have been diagnosed with severe major depressive disorder (single or recurrent episode) - Your depression score on a standard rating scale is high (MADRS ≥24) - You are not currently pregnant **You may NOT be eligible if...** - You have bipolar disorder, psychosis, or schizophrenia - You have a serious neurological condition such as epilepsy or dementia - You have significant heart, liver, or kidney disease - You are currently at high risk of suicide requiring immediate hospitalization Talk to your doctor to see if this trial is right for you.