A recent meta-analysis of 15 randomised, double-blind, placebo-controlled studies, has added further weight to the ever increasing evidence for the role of omega-3 EPA in treating depression. Researchers from the University of Illinois at Chicago, led by Professor John Davis, found that patients taking omega-3 with either EPA or a combination of EPA and DHA at a ratio favourable to EPA, experienced clear antidepressant benefits. Indeed, it is apparent that, as the proportion of EPA increases within a preparation, so does the efficacy of the oil. In addition, what was clear across studies was that patients taking the pure DHA form of omega-3 experienced no antidepressant effect. These findings, along with a previous meta-analysis conducted late in 2009, appear to explain why some studies, in which DHA was the predominant fatty acid within the supplement, concluded that long chain PUFA supplementation was ineffective in depression. Indeed, these studies simply did not take into account the possible differential effects of EPA versus DHA. There is certainly evidence pointing towards a clear structural role for DHA with a contrasting functional role for EPA and this itself appears to be significant. Therefore, simply labelling EPA and DHA as ‘omega-3’ devalues their individual roles. Currently, using pure ethyl- EPA at a dose of around 1g/daily appears to be the most efficacious long-term treatment.
With regard to depression itself, this debilitating condition is being recognised as a complex interaction of stress-coping mechanisms, exaggerated inflammation, coupled with decreased levels of neurotransmitters known to regulate mood, such as serotonin, noradrenaline and dopamine, with levels of omega-3 directly correlated with depressive symptoms. Treatment with EPA has been shown to reduce levels of inflammatory products associated with stress, regulate neurotransmitter levels and normalise omega-3 levels. Furthermore, circulating EPA not only protects DHA degradation from cell membranes, but is also efficiently converted to DHA where necessary. Given that the majority of antidepressants, as well as other prescription drugs used in the treatment of clinical depression, can cause side effects severe enough to influence compliance to the treatment, it is not surprising that there is demand for a safe and efficacious alternative to current pharmaceuticals from both patients and practitioners. With the increasing recognition that omega-3 deficiencies are a predominant feature of clinical depression, supplementation with specific long chain fatty acids as a viable treatment option in the treatment of depression is now the focus of many peer-reviewed studies. With the overwhelming and constantly increasing evidence for EPA in depression, it should be seriously considered that the pathway to prescription be opened as an accessible and recognisable alternative to current treatments.