The largest study of its kind about the effects of nutrient supplementation on mental health found strong evidence that some supplements -- especially omega-3 -- can be an effective additional treatment for some mental disorders in support of conventional medical therapy

To reach this conclusion, an international team of scientists led by the NICM Health Research Institute, Western Sydney University in Australia conducted the world's largest review (or a meta-synthesis) of top-tier evidence in this regard.

They examined 33 meta-analyses of randomized control trials (RCTs) and data from 10,951 people with mental health disorders. These illnesses included depression, stress and anxiety disorders, personality disorders, schizophrenia, bipolar disorder and attention-deficit/hyperactivity disorder (ADHD).

The results, which were published in an online study this week in World Psychiatry, found strong evidence that certain supplements could be an effective treatment for some mental disorders in concert with conventional treatment. The study also found that most nutritional supplements assessed didn't significantly improve mental health but those that did were beneficial.

It also found all nutrient supplements were safe within recommended dosages and prescription guidelines. There was no evidence of serious adverse effects or contraindications with psychiatric medications.

"While there has been a longstanding interest in the use of nutrient supplements in the treatment of mental illness, the topic is often quite polarizing, and surrounded by either over-hyped claims or undue cynicism," Dr Joseph Firth, lead author of the study, said. Dr Firth is also Senior Research Fellow at the NICM Health Research Institute and Honorary Research Fellow at The University of Manchester in the United Kingdom.

"In this most recent research, we have brought together the data from dozens and dozens of clinical trials conducted all over the world, in over 10,000 individuals treated for mental illness."

Dr Firth said this mass of data allowed the research team to investigate the benefits and safety of various different nutrients for mental health conditions "on a larger scale than what has ever been possible before."

Omega-3 supplements were found the most beneficial as a supplement for mental health by the study. The study said there is strong evidence for omega-3 supplements as an add-on treatment for major depression. Omega-3 supplements helped reduce the symptoms of depression beyond the effects of antidepressants alone.

The study said there is also some evidence to suggest omega-3 supplements might also have small benefits in ADHD.

The amino acid N-acetylcysteine could be a useful adjunctive treatment in mood disorders and schizophrenia, and the study found emerging evidence for this observation.

Special types of folate supplements might be effective as add-on treatments for major depression and schizophrenia.

On the other hand, the study found no strong evidence for omega-3 for schizophrenia or other mental health conditions. It also said there is currently a dearth of compelling evidence supporting the use of vitamins (such as C, D and E) and minerals (zinc and magnesium) for any mental disorder.

The study said its findings should be used to produce more evidence-based guidance about the usage of nutrient-based treatments for various mental health conditions.

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