A new review from researchers in the United Kingdom has highlighted four dietary supplements—St. John’s wort, probiotics, vitamin D, and saffron—that present the strongest evidence for easing depressive symptoms, according to an analysis published this week in Health.com (health.com). The study, which assessed hundreds of clinical trials covering 64 different over-the-counter supplements, arrives as Thailand and the world see surging interest in self-care for mental wellbeing amid persistent stigma around psychiatric treatment.
Depression remains a significant health concern in Thailand, with the Department of Mental Health estimating that more than 1.5 million Thais suffer from depressive disorders, while many more go undiagnosed or untreated due to social stigma or limited access to professional mental health care (who.int). The hope for cheap, easily accessible remedies has bolstered the global supplements market, now valued at nearly $152 billion, and fueled widespread social media promotion of “mood-boosting” products. Yet, as this review reveals, most supplements lack solid clinical evidence of efficacy.
In their analysis of over 200 trials, the UK researchers found that the vast majority of supplements—ranging from folic acid to magnesium, cinnamon, and vitamin C—either hadn’t been adequately studied or showed no significant benefit over placebo. Notably, 41 supplements had only been tested in a single trial each, leaving their potential effects on depression far from conclusive.
Among those assessed, only four emerged as clearly outperforming placebo: St. John’s wort, derived from the yellow-flowered Hypericum perforatum; probiotics, which support gut health; vitamin D, critical to immune and neurological function; and saffron, the culinary spice harvested from crocus flowers. Large-scale clinical trials found St. John’s wort may rival prescription antidepressants, while early saffron studies also indicated positive effects, albeit with more research needed. Probiotics and vitamin D showed benefit, especially for individuals with deficiencies—though scientific certainty about their overall effect remains elusive.
Dr. De Borrah Wright, medical director at a major public hospital in New York, commented, “What stood out most to me is that they looked at 64 different products but found solid evidence for only four. It highlights how important it is not to assume that every supplement on the shelf is effective” (health.com).
Local mental health practitioners echo the importance of skepticism, especially in Thailand where unregulated herbal products are widely available in pharmacies, fresh markets, and increasingly through e-commerce. According to a senior psychiatrist at the Department of Mental Health, “Thai consumers must remember that supplements, even those labelled as ‘natural,’ can interact with prescription medications, including antidepressants, blood thinners, and birth control—sometimes dangerously so.” This is particularly relevant for St. John’s wort, which can reduce the effectiveness of several common medications (mayoclinic.org).
In terms of biological mechanisms, researchers observe that both St. John’s wort and saffron appear to regulate the brain’s serotonin and dopamine levels—hormones closely tied to mood regulation. Vitamin D has receptors in brain regions implicated in depression, such as the prefrontal cortex, hippocampus, and thalamus, suggesting its deficiency could contribute to depressive symptoms. Meanwhile, probiotics improve gut health, potentially affecting the gut-brain axis—a communication channel increasingly linked to mental health (ncbi.nlm.nih.gov).
The review did not strictly assess study quality, however, meaning some positive outcomes may have emerged from less rigorous research. This limitation is not unique to supplement research, but it underscores the need for more large-scale, high-quality studies before supplements can be confidently recommended as a substitute for—or even an adjunct to—conventional medical therapy.
For Thai readers, an important cultural factor is trust in herbal and traditional medicine, which remains central in many communities. Hypericum perforatum, for example, is mostly imported and not native to Thai traditional medicine, though local practitioners sometimes recommend herbal blends containing similar ingredients. Saffron and probiotics are already popular health products and supplements, available in supermarkets, pharmacies, and increasingly through online platforms. Vitamin D deficiency is also being recognized as a concern, especially among urban dwellers with limited sunlight exposure.
At present, Thai doctors caution against viewing supplements as a complete replacement for professional mental health care. “Supplements can form part of a holistic approach towards better mental wellness, especially if guided by a healthcare provider,” said a clinical psychologist at a major Bangkok hospital, “but they should never delay or replace counseling or prescribed antidepressants for moderate or severe depression.” This advice resonates even more as many Thais—like people worldwide—often confront depression in silence, deterred by societal stigma or fear of discrimination.
The researchers did note that adverse events from supplements in the reviewed studies were relatively low. Nevertheless, the lack of regulatory oversight—including by Thailand’s Food and Drug Administration—means quality and dosage can vary significantly between brands. Both international and local experts recommend purchasing supplements that carry a seal or approval from an established third-party agency (such as USP or NSF) to minimize the risk of contamination or mislabeling (health.com). In Thailand, the “GMP” label is commonly found on locally manufactured supplements, but this only certifies production conditions, not actual efficacy.
International comparisons provide additional perspective. In many Western countries, supplement use is generally higher but so too is regulatory scrutiny. In the US, for instance, the Food and Drug Administration does not regulate supplements for efficacy, only stepping in when products are flagged for safety issues. In Thailand, imported supplements—especially “natural” brands from Australia or Germany—have strong market appeal, but face similar issues of inconsistent quality and incomplete evidence for most mental health claims (newatlas.com).
As for future developments, the review’s authors hope their findings will steer research funding toward large, high-quality trials of the most promising products, closing the evidence gap that has allowed misinformation to flourish. With mental health now an explicit focus of Thailand’s national health agenda and greater public awareness of depression, such research will be critical to informing safe, effective care options that integrate biomedical and traditional paradigms.
For practical steps, Thai readers considering depression supplements are advised to:
- Consult with a healthcare professional, especially if already taking prescription medications.
- Choose products with quality certification; beware of exaggerated claims online or from unlicensed sellers.
- Recognize that even “natural” remedies can have side effects or interfere with other medications.
- Use supplements as part of a broader approach to mental wellbeing—including regular exercise, time outdoors, supportive social networks, and professional mental health care as needed.
- Stay updated on new research and government advisories regarding supplement efficacy and safety.
Ultimately, as stated by Thea Gallagher, PsyD, a US-based psychologist, “It’s kind of the wild wild west with understanding supplements, and we are trying to learn a lot more about how they work and what they do. If supplements are part of you turning over a new leaf of taking better care of your health, that can be part and parcel good for depression—but science isn’t yet robust enough for strong recommendations” (health.com). For Thai society, a careful blend of modern science, traditional wisdom, and medical oversight may hold the safest and most effective path forward.