• Score on the depression rating scale [ Time Frame: Measured at Week 12 ] [ Designated as safety issue: No ]
  
• Brain energy metabolism [ Time Frame: Measured at Weeks 2 and 12 ] [ Designated as safety issue: No ]
  

Major depressive disorder (MDD) is a severe form of depression. MDD can significantly interfere with an individual's thoughts, behavior, mood, and physical health. People who suffer from MDD often experience feelings of worthlessness; they may feel hopeless and may be unable to cope with problems in their life. In addition, they often experience sleep disruption, loss of appetite, and chronic pain.

Antidepressant medications are often prescribed for treating MDD; however, 30% to 40% of individuals fail to respond adequately to medication. Preliminary research has shown that lower levels of brain energy metabolism are often associated with MDD. No studies have yet shown whether there is a difference in brain energy metabolism between individuals who respond well to antidepressants versus those who do not. Escitalopram is an antidepressant medication often used to treat MDD. It causes a calming effect and reduces anxiety by increasing the amount of serotonin in the brain. This study will compare the changes in brain energy metabolism due to treatment with escitalopram in individuals with MDD. In turn, these findings may aid in understanding the relationship between brain energy metabolism and depression, and may guide future antidepressant trials.

This 12-week study will enroll individuals diagnosed with MDD, as well as healthy individuals. During Weeks 1 through 4, participants with MDD will receive 10 mg of escitalopram on a daily basis. If a participant does not respond well to the medication, as determined by the study clinician, the dose may be increased to 20 mg per day for Weeks 5 through 8. If a participant continues to not respond to the medication after 8 weeks, the dose may be increased to 30 mg per day for Weeks 9 through 12. Study visits will occur every other week throughout the 12 weeks. Laboratory tests, physical examinations, and vital sign measurements will be performed at each study visit. Outcome measurements will include depression levels as assessed by standardized psychological tests and questionnaires, as well as brain energy metabolite levels as assessed by magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) scans. The MRS and MRI scans will occur at baseline, Week 2, and Week 12; the entire scanning procedure will last 70-80 minutes. Following the end of the study, all participants will be offered follow-up medical care for 3 months. Participants who responded well to escitalopram will be offered continued treatment with the drug, while those who did not respond well to escitalopram will be offered treatment with another antidepressant.