Patients with major depressive disorder (MDD) commonly have many gastrointestinal complaints. Gastrointestinal pain is classified into 2 categories: visceral and somatic pain. The main aim of this study is to compare somatic and visceral sensitivity between healthy people and pateints with MDD. These two sensitivities will be assessed by the 2 following tests: standardized rectal distension and Transdermal transcutaneous electric nerve stimulation. Thereafter, patients with MDD will be randomly allocated to escitalopram or reboxetine. After 6 weeks of treatment, somatic and visceral sensitivity will be reassessed.

Inclusion Criteria:

• MDD according with DSM-IV-TR
• Hamilton depression scale > 21

Exclusion Criteria:

• history of gastrointestinal illness
• history of escitalopram, citalopram or reboxetine allergy.
• history of escitalopram, citalopram or reboxetine resistant depression.
• other axis I psychiatric disorder.
• a punctuation > 2 on the suicide item of the Ham-D.
• history of ECT during the past 6 months.
• pharmacological failure of the present depressive episode.
• pregnancy or nursing.
• treatment with drugs that may interact with study medication.