Desvenlafaxine Monotherapy in Dysthymia

Inclusion Criteria: * Male and female patients between 18-65 years. * Primary diagnosis of Dysthymic Disorder, as defined by DSM-IV criteria (300.4). * MADRS score ≥15 at Screening and Baseline. * Supportive therapy, and use of zopiclone for sleep and low-dose benzodiazepines on an as needed basis for anxiety, is allowed at any time. * Written informed consent Exclusion Criteria: * Co-morbid diagnosis of any other Axis I disorders (other than anxiety disorders such as Generalized Anxiety Disorder, Social Anxiety Disorder and Post-traumatic Stress Disorder, provided that Dysthymic Disorder is currently the diagnosis). * Meet DSM-IV criteria for a current episode of major depression within two months prior to screening or who have received treatment for a major depressive episode within six months prior to screening. * Substance abuse or dependence including alcohol, within 6 months prior to screening. * Patients on the following prohibited treatments: 1. Psychotropics such as other SSRIs, other SNRIs, lithium, sibutramine, tramadol, St. John's Wort, within 2 weeks of randomization 2. Agents that impact significantly on serotonin metabolism (e.g. MAOIs, tryptophan, triptans) within 2 weeks of randomization * Have received physical therapies for depression (e.g. ECT, rTMS) within the 3 months prior to randomization. * Previous non-response to a therapeutic trial of desvenlafaxine (at least 50 mg/day for 2 months). * Clinically significant abnormalities in hematology, clinical chemistry, urinalysis or ECG at the screening visit, as judged by the Principal Investigator. * Presence of medical or psychiatric condition deemed by the Investigator to interfere with study procedures or endpoint data.