Australians have long been some of the highest users of herbal and nutritional supplements that claim to boost mood or ease depression. These include omega-3s (found in fish oil), St John’s wort, probiotics, and vitamin D.
In fact, among Australians with depression, these supplements are more popular than prescription medicines.
But do they actually work? And how do they compare to other treatments? A new review has assessed the evidence from 209 studies—here’s what it found.
Do these supplements work?
The new study aimed to assess the international evidence available for common over-the-counter products for depression in adults aged 18–60.
Despite their widespread popularity and availability, the study found there is surprisingly little research on these therapies, compared with psychological therapies and prescription antidepressants.
Only a few products had a relatively large body of evidence suggesting they were effective at treating symptoms. These were omega-3 supplements, St John’s wort, saffron, probiotics, and vitamin D.
However, most products had only a single trial examining their use.
The researchers noted there was promising evidence for some herbal and nutritional supplements, where multiple studies did exist. These included folic acid, zinc, Rhodiola, lavender, and lemon balm. But there is not enough evidence yet to recommend them, so more studies would be needed.
What does other research say?
These findings appear to support previous research assessing supplements for depression.
In 2024, the Australian government’s review of natural therapies also found moderate evidence that several herbal medicines can relieve symptoms in mild to moderate depression. These include curcumin (from turmeric), saffron, and St John’s wort.
It also found moderate evidence St John’s wort was as effective as conventional antidepressants.
However, the major caveat is that much of the existing evidence relates to mild to moderate depression.
While some products were found to have some effect in major depressive disorders—probiotics, for example—there is little evidence to suggest they’re effective where a large number of symptoms exist.
Dose and quality vary
The dose and quality of over-the-counter products can also vary significantly, which can make it difficult to identify appropriate products or assess which ones work.
In the United Kingdom, official advice for healthcare practitioners acknowledges there is evidence St John’s wort can help with less severe forms of depression. But it also advises caution in recommending it, given how much the dose, preparation, and quality can vary between different herbal products.
In Australia, guidelines for psychiatrists treating mood disorders such as depression note that good evidence exists for using omega-3 fatty acids (fish oils). But they highlight that there only seems to be a benefit when the product has 60% or more eicosapentaenoic acid (one of the main types of omega-3).
Whether folate supplements are effective for depression can depend on their form, which active ingredient is used, and how well the body can absorb it.
There may be other nuances in other supplements that we need more research to understand.
Are there any risks or downsides?
The study also concluded these products present few safety issues, whether used alone or in combination with other treatments. This is the reason most remain available over the counter.
However, herbal medicines and dietary supplements also contain chemicals that can work like drugs and interact with other medications.
For example, the way St John’s wort works on neurotransmitters (the body’s chemical messengers) is similar to many prescription antidepressants.
So taking it alongside antidepressants can lead to serotonin syndrome, a condition that can lead to fever and seizures in extreme instances. In rare cases, you may experience similar side effects to taking antidepressants.
However, many of these treatments are not only safe but more effective when used together with conventional treatments for depression.
For instance, some studies suggest omega-3 supplements used in addition to standard antidepressant therapy resulted in the best outcomes. But more research is needed to explore this link.
How do they stack up against other therapies?
Pharmaceutical medications, such as antidepressants, and talk therapies remain the gold standard in Australian guidelines for mood disorders. They are the most studied interventions for these disorders, which means we have the most evidence for how well they work.
However, emerging evidence is developing for other therapies too.
Lifestyle interventions to improve diet and exercise have been shown to be as effective in addressing symptoms of depression as receiving psychological treatment alone.
Nutrients are the building blocks of many body processes, and some nutrient deficiencies themselves (such as iron and B12) can cause depressive symptoms. So their potential role of nutritional supplements is perhaps unsurprising.
However, research—including our own—increasingly demonstrates eating nutrient-rich foods (rather than taking supplements) can be enough to improve symptoms in mood disorders such as depression.
The Australian government’s review of natural therapies also found the evidence for non-pharmacological treatments, such as yoga, was more certain than for herbal medicines and nutritional supplements in treating depression.
It’s also important to note that depressive symptoms rarely present alone. They can be secondary to other underlying health conditions (such as hypothyroidism) or present with other conditions.
Investigating and addressing these potential root causes and improving general health is essential in managing symptoms.
What are the key takeaways?
Some herbal and nutritional supplements do appear to have a potentially beneficial effect for less severe forms of depression. But for many of these therapies, there is still not enough evidence to offer definitive recommendations.
While the Therapeutic Goods Administration regulates the safety and quality of supplements, there is still variation in product quality, dose, and how well the body can absorb it.
If you’re thinking of using herbal or nutritional supplements, it’s important to consult a health professional, such as a GP, naturopath, or even a psychologist.
If this article has raised issues for you, or if you’re concerned about someone you know, call Lifeline on 13 11 14.
More information:
Rachael Frost et al, Understanding the research landscape of over-the-counter herbal products, dietary supplements, and medications evaluated for depressive symptoms in adults: a scoping review, Frontiers in Pharmacology (2025). DOI: 10.3389/fphar.2025.1609605
This article is republished from The Conversation under a Creative Commons license. Read the original article.
