The review published today collated data from 26 randomised trials involving a total of 1,458 participants.
The trials all looked at the impact of omega-3 fatty acid supplements on major depressive disorder, otherwise known as clinical depression or recurrent depression.
One small study found comparable benefits in its direct comparison of omega-3 and anti-depressants, however the review said the quality of this evidence was very low.
“Our primary analyses suggest a small-to-modest, non-clinically beneficial effect of n-3PUFAs [polyunsaturated fatty acids] on depressive symptomology compared to placebo, although the effect size estimate is imprecise, and the quality of the evidence on which this result is based is low to very low,” wrote the researchers from the University of Bristol, University Hospitals Bristol Education Centre and Bournemouth University.
Commenting on the findings, lead author and associate psychology professor at Bournemouth University Dr Katherine Appleton said the effect seen in some of the studies was “unlikely to be meaningful to people with depression” and added that all of the studies included were small and of low quality.
According to the World Health Organisation (WHO), around 350 million people of all ages suffer from depression.
Over 800,000 people die due to suicide every year and suicide is the second leading cause of death in 15-29-year-olds.
“At present, we just don’t have enough high quality evidence to determine the effects of omega-3 fatty acids as a treatment for major depressive disorder. It’s important that people who suffer from depression are aware of this, so that they can make more informed choices about treatment.”
Adam Ismail, executive director for the Global Organization for EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) omega-3s (GOED), echoed the “monster” 120-page paper’s call for larger trials.
However he said overall the findings so far were “quite supportive” of the association between EPA and DHA consumption and benefits in major depression.
For EPA and predominantly EPA supplements, the benefits reached levels that were both clinically and statistically significant.
“In addition, some of the biggest benefits were seen in trials where omega-3 supplements were administered with concomitant medications for depression. This really underscores that increasing omega-3 intake can be a positive nutrition and lifestyle change that could support existing depression treatments,” he told us.
For the European Alliance Against Depression (EAAD), the review confirmed there was “no effective alternative” to treatment with antidepressants and/or psychotherapy.
“The COCHRANE protocol sends out an important message to patients and the broad public as to get help through professional treatment options as depression cannot be treated by taking supplements as the main therapeutic regimen,” a spokesperson for the NGO said.
However, it added there had been some promising research into the preventative potential of omega-3s and depressive symptoms.
The EU-funded project MooDFOOD is currently examining the relationship between nutrition and depression with a large-scale randomised clinical trial in four European countries.
Adverse effects & false hope
The review also looked at side effects of omega-3 supplements compared to anti-depressants.
While there has been some evidence of mild gastrointestinal issues, the review said assessment was so far incomplete.
“The data on adverse events and failure to complete are again of low quality, but given the high rates of adverse events associated with some antidepressants, n-3PUFAs may offer an alternative treatment of possible benefit and reduced side effects.
“However, whether all possible negative side effects are studied in trials is questionable, and high dropout rates as a result of lack of improvement testify to the negative side effects of false hope.”
Ismail said it was important to consider possible side effects like mild gastrointestinal issues in the context of “more serious side effects associated with many depression medications.”
He added that the European Food Safety Authority (EFSA) and the Norwegian Scientific Committee for Food Safety (VKM) had concluded there were no safety concerns associated with EPA and DHA intakes of 5.0 and 6.9 grams/day, respectively.
EPA and DHA are backed by EFSA for brain, eye, foetus and cardiovascular benefits under the EU's tough nutrition and health claims regulation (NHCR).
Source: Cochrane Database of Systematic Reviews
Published online ahead of print, DOI: 10.1002/14651858.CD004692.pub3
“Omega-3 fatty acids for depression in adults”
Authors: K.M. Appleton, H.M. Sallis, R. Perry, A.R. Ness, R. Churchill