The investigators will be looking at MAO-A density before and after seven weeks of treatment with an antidepressant and dietary supplement. MAO-A is an enzyme that breaks down brain chemicals that regulate mood. MAO-A density is elevated in patients with major depressive episodes (MDE) secondary to major depressive disorder (MDD). Many remain treatment resistant with common antidepressant treatments and we think it may be due to poor targeting of brain pathologies. We want to test if adding a dietary supplement may normalize MAO-A.

All subjects are getting the combined treatment of a selective serotonin reuptake inhibitor and the dietary supplement. There are two possible selective serotonin reuptake inhibitor treatments but the dietary supplement remains the same. No subjects are receiving the selective serotonin reuptake inhibitor alone and no subjects are receiving the dietary supplement alone. The dietary supplement is called n-acetylcysteine.

Inclusion Criteria:

• DSM-IV diagnosis of current major depressive episode and major depressive disorder
• Hamilton Depression Rating Scale score of at least 20

Exclusion Criteria:

• Comorbid axis I or II disorders
• Antidepressant use in past 6 months
• Current use of herbal remedies
• Cigarette smoking
• Drug or medication use within past 8 weeks
• History of substance abuse/neurotoxin use
• History of psychotic symptoms
• History of CNS medical illness
• Current substance use
• Test positive on pregnancy test (women)