The efficacy of herbal supplements is a topic of ongoing research and debate. While some studies suggest benefits, others find little to no effect. For example, [St. John's wort](https://pubmed.ncbi.nlm.nih.gov/) has been shown in some studies to help with mild to moderate depression, but the evidence is not conclusive. Epidemiologists use various study designs, such as [randomized controlled trials](https://pubmed.ncbi.nlm.nih.gov/) and [cohort studies](https://pubmed.ncbi.nlm.nih.gov/), to assess these supplements' effectiveness.
