Anxiety is the most common psychiatric disorder: One in three people will experience the debilitating condition – characterized by inappropriate or exaggerated fear – in their lifetime. Though many effective pharmaceutical and psychological treatments already exist, many affected people struggle to find one that works for them, grapple with high costs, or suffer from serious side effects. Thus, there is a huge unmet need for safe, affordable, and simple solutions.

Enter omega-3 polyunsaturated fatty acids (PUFAs). This family of molecules, found in plant and fish oils, is a hot item in medical research thanks to past studies linking high-intake diets to reduced inflammation, improved cardiovascular health (though this is up for debate), and better cognitive abilities in children. There is also substantial evidence that omega-3s are essential to normal biochemical functioning in the adult brain – they are, after all, a critical ingredient of nerve cell membranes – and that deficiency can lead to dementia and behavioral disorders, including anxiety.

But the evidence that omega-3 supplements can reduce the symptoms of anxiety in people (as opposed to rats or mice) has been mixed so far. Hoping to clarify the fatty acids’ potential for this application, teams led by Professor Kuan-Pin Su in Taiwan and Dr Yutaka Matsuoka in Japan have waded into the literature and performed a meta-analysis.

Their results, published in JAMA Psychiatry, may make you consider adding a bottle of fish oil pills to your next Amazon shopping cart.

“Although participants and diagnoses were heterogeneous, the main finding of this meta-analysis was that omega-3s were associated with significant reduction in anxiety symptoms compared with controls; this effect persisted vs placebo controls,” they wrote. 

The teams looked at 19 studies with a broad range of designs and patient inclusion criteria. A total of 1,203 participants comprised 16 placebo-controlled and three non-controlled investigations. To account for the influence of the placebo effect as much as possible, the authors also analyzed the placebo studies separately. Importantly, they found a pattern wherein individuals taking some amount of daily omega-3 PUFAs were more likely to report reduced anxiety symptoms than those taking a sham supplement.  

Interestingly, the five studies that recruited participants without a specific clinical diagnosis of anxiety did not show a significant association between daily omega-3 supplements and symptom relief, yet the 14 studies that restricted participants to those with specific clinical diagnoses did. In regards to what dosage holds the most promise, the available data suggest that a regimen of 2,000 milligrams or more per day has better anxiety-reducing properties than lower doses.  

In an email to IFLScience, Su and Matsuoka explained that the psychiatric community has remained equivocal about omega-3s, despite the findings of studies such as these, because single treatments (even good ones) only show limited measurable effects against complex diseases like anxiety.

"Indeed, it is very easy to miss the small signals of therapeutic efficacy in placebo-controlled clinical trials and/or meta-analytic reviews without careful considerations on study designs," they said.

Due to the high chance of confounding from inconsistent participant demographics and methodology across the 19 studies, on top of their modest sample sizes, the authors told IFLScience that more well-conducted clinical trials would be needed before they could recommend omega-3 PUFAs as a first-line treatment for anxiety.

"However, for patients who are not responsive to traditional anxiety treatment such as antidepressants or psychotherapies, omega-3 PUFAs might be a promising alternative and adjunctive treatment with great safety profiles," they said.

Dr Matsuoka is now planning a phase two randomized control trial on omega-3s for anxiety in cancer survivors, and Professor Su hopes to initiate one on physical anxiety symptoms in patients with depression.