This is a study of the effectiveness of adding Abilify (aripiprazole), an atypical antipsychotic medication, to ongoing selective serotonin reuptake inhibitor (SSRI) antidepressant treatment for depressed outpatients who are not responding fully to SSRI treatment alone. It is hypothesized that patients' functioning will improve after 12 weeks of treatment with Aripiprazole and SSRI medication.

This is a pilot study of the effectiveness of adding Abilify (aripiprazole), an atypical antipsychotic medication, to ongoing selective serotonin reuptake inhibitor (SSRI) antidepressant treatment for depressed outpatients who are not responding fully to SSRI treatment alone. Fifteen subjects will be given aripiprazole in a flexible dosing schedule and followed for 12 weeks, while continuing their ongoing SSRI medication. Assessments of depressive symptoms, overall functioning, social functioning, and side effects will be completed. It is hypothesized that patients' functioning will improve after 12 weeks of treatment with Aripiprazole and SSRI medication.

Inclusion Criteria:

• Male and female outpatients between the ages of 18 and 70.
• Patients with a principal Diagnostic and Statistical Manual fourth edition (DSM-IV) diagnosis of Major Depressive Disorder, unipolar, nonpsychotic type
• Patients with a total of 14 or higher on the 17-item Hamilton Depression Scale at baseline
• Patients who have had treatment with an SSRI at an adequate dose (see Table for a minimum of 6 weeks (i.e. 6 wks at the dose defined as adequate in Table 2)
• Patients who agree to use acceptable method of birth control throughout the study

Exclusion Criteria:

• Patients with any of the following DSM-IV diagnoses: Delirium, Dementia, Amnestic, or other Cognitive Disorders. Bipolar Disorder or cyclothymia, Schizophrenia, Delusional (Paranoid) Disorders and Psychotic Disorders not elsewhere classified, Severe Borderline Personality Disorder, Anorexia Nervosa, or Bulimia.
• Patients who, within the past 6 months, met DSM-IV criteria for abuse of or dependence on any drug, including alcohol.
• Patients who are pregnant or nursing women.
• Patients who would pose a serious risk for suicide during the course of the study, as evidenced by one of the following: (a) report of having a specific plan for killing themselves, (b) a score of 3 or higher on the Hamilton Depression Rating Scale item #3 as rated by the treating clinician at Week 0, or (c) a suicide attempt within the last 6 months which required medical attention, such as an emergency room visit or which is considered by the treating physician to have been possibly life threatening
• Patients with unstable medical conditions such as untreated or uncontrolled hyperthyroidism, hypothyroidism, hypertension (defined as blood pressure>150/90), cardiovascular disease, diabetes, HIV (by report of patient).
• Patients with a history of seizures.

16 weeks, during and after the clinical trial

Open label study without comparison group.