Phospholipid Hypothesis of Depression: From Molecular Biology, Neuroimaging to Behaviour

There are several important questions to answer regarding phospholipid polyunsaturated fatty acids (PUFAs) hypothesis of depression. Firstly, although case-control studies revealed that depressive patients had lower levels of omega-3 PUFAs, the abnormal findings in individual PUFA of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) or arachidonic acid (AA) are not consistent. Secondly, the deficits in n-3 PUFAs are related to their metabolic enzymes. However, the association study of polymorphisms of PUFA-metabolism related genes in depression is limited. Thirdly, the active component of antidepressant effect in n-3 PUFAs is still in debate. Fourthly, the molecular mechanisms of n-3 PUFAs' antidepressant effects have yet to be elucidated in human brain functional neuroimaging or in cellular models.

This 3-year proposal is divided into 2 clinical studies. In study 1, the investigators aim to test the clinical and biological effects of n-3 PUFAs (EPA: 3.5 g/d and DHA: 1.75 g/d versus placebo: high oleic oil) for depressive symptoms in a 12-week, double-blind, placebo-controlled trial of patients with drug-free MDD. In study 2, the investigators will measure the biological and neuroimaging markers to investigate the biological mechanisms of EPA (3.5 g/d) versus DHA (1.75 g/d) in 12-week, double-blind, randomized-controlled trial with patients with drug-free major depression disorder (MDD).

Inclusion criteria

• Diagnostic and Statistical Manual (DSM)-IV criteria for major depressive disorder
• Age being age 18-65.
• Capacity and willingness to give written informed consent.
• Free from antidepressants, mood stabilizers, and antipsychotics for more than 4 weeks.

Exclusion criteria

• Any major medical illnesses.
• A recent or past history of any Axis-I diagnoses besides major depressive disorder, including psychotic disorders; cognitively impaired mental disorders; impulse control disorders; substance use disorder or substance abuse (last 6 months prior to the studies); primary anxiety disorders, including post-traumatic stress disorder and panic disorder; and bipolar disorders; or Axis-II diagnoses, i.e. borderline and antisocial personality disorder.