• Relationship between depression symptoms and brain physiologic measures [ Time Frame: Measured at exit from Level 1 treatment or from Level 2 treatment (each 12 weeks duration) ] [ Designated as safety issue: No ]
  

• Patient acceptability of EEG measures [ Time Frame: Measured after final EEG recording ] [ Designated as safety issue: No ]
  
• Relationship between brain physiologic measures and side effects [ Time Frame: Measured at study exit ] [ Designated as safety issue: No ]
  
• Relationship between brain physiologic measures and quality of life measures [ Time Frame: Measured at study exit ] [ Designated as safety issue: No ]
  
• Relationship between brain physiologic measures and psychosocial function measures [ Time Frame: Measured at study exit ] [ Designated as safety issue: No ]
  
• Relationship between brain physiologic measures and durability of remission, assessed as return of depressive symptoms during the 6 month follow-on phase [ Time Frame: Measured at Month 6 of follow-on phase ] [ Designated as safety issue: No ]
  

Depression is a serious medical illness that is characterized by a persistent sad, anxious, or empty mood. Many treatments have been shown to relieve depression, including both medications and behavioral therapies. No single treatment, however, works for everyone. Approximately half of the people being treated for depression do not respond to the first medication they try. Studies have shown that some people with depression show changes in brain activity within 2 weeks of starting treatment, even though symptoms do not change until later. People who do not respond to treatment, however, do not exhibit these changes in brain activity. More information is needed to understand the different ways in which people with depression respond to medication. This study will examine how brain activity is affected by antidepressant treatment and how changes in brain activity relate to treatment response in people with depression. It will also determine whether the brain testing involved in this study is burdensome to the participants.

Individuals interested in taking part in this 1-year study will first attend one screening visit to determine their eligibility for participation. Before beginning treatment, all participants will have an electroencephalogram (EEG) to determine baseline brain activity. Participants will then receive up to 12 weeks of treatment with escitalopram, an antidepressant medication. Study visits will be held every 2 to 3 weeks during this phase. At the Week 2 visit, participants will have another EEG. Participants who respond to escitalopram by the end of the treatment phase will be asked to participate in a 6-month follow-up phase, in which participants will be followed by their own personal physicians, but will have the option to continue treatment with escitalopram. Follow-up visits will be held at Months 3 and 6. Participants who do not respond to escitalopram by the end of the treatment phase will have another EEG, and will then receive up to 12 weeks of treatment with sertraline, another antidepressant medication. Study visits will be held every 2 to 3 weeks, and participants will have a fourth EEG at Week 2. Participants who respond to sertraline will then enter the 6-month follow-up phase, and may continue receiving sertraline. Participants who do not improve with sertraline will receive referrals for additional care outside of the study.