The purpose of this study is to determine whether augmentation of antidepressant medication with Omega-3 polyunsaturated fatty acids increases the speed and degree of improvement for patients with major depression

The study will be a 4 week, parallel-group double blind randomised control trial of the efficacy pf Omega-3 as an augmentor of antidepressant treatment for depression. People aged between 18 and 65 with a first or new episode of depression warranting treatment with antidepressant medication will be recruited. In addition to their antidepressant medication, participants will be randomly allocated to receive either Omega-3 (fish oil) or placebo (paraffin oil)for 4 weeks. Participants will commence treatment with the antidepressant and Omega-3/placebo simultaneously. Participants will be followed up at 1,3 and 4 weeks and will be asked to rate their mood daily for the 4 week study period. Blood samples will be taken pre and post treatment to measure change in Omega-3 levels.

Inclusion Criteria:

• Participants must present with a first or new episode of DSM IV non-psychotic major depression warranting treatment with antidepressant mediation.
• Must be able to give informed consent.

Exclusion Criteria:

• History of psychosis or mania/hypomania or personality disorder.
• Non-English speaking or otherwise unable to provide historical information.
• Having taken Omega-3 dietary supplements in the last 3 months.
• History of allergy to Omega-3 supplements, finfish or shellfish.
• Pregnancy, breast feeding or plans to become pregnant during course of study.
• Post-natal depression
• Current drug or alcohol abuse or dependence or history of abuse or dependence over the last 12 months.
• Unstable thyroid function
• Hepatic or renal impairment or other medical conditions that may interfere with the absorption and metabolism of Omega-3 polyunsaturated fatty acids
• Coagulopathy or anticoagulant treatment due to theoretical bleeding risk.
• Patients who, in the investigator's judgment pose a current serious suicidal or other safety risk, or patients who will not likely be able to comply with the study protocol.