Efficacy and Safety of Herbal Supplements with Anxiolytic, Antidepressant, and Sedative Action: A Review of Clinical Data and Toxicological Risks

Background/Objectives: Plant-based supplements are widely used for the management of anxiety, depression, and insomnia. Despite their over-the-counter availability and perceived safety, these products may pose relevant pharmacological and toxicological risks. This narrative review critically evaluates clinical evidence on commonly used herbal preparations, with particular emphasis on herb–drug interactions, adverse effects, and issues related to product adulteration. Methods: Major scientific databases (PubMed, Scopus, and Web of Science) were searched to identify clinical studies evaluating plant-based supplements for mental health and sleep disorders. Data on study design, dosage, efficacy, and adverse events were analyzed, together with regulatory information and reports of product adulteration and quality concerns. Results: Herbal supplements such as Hypericum perforatum, Passiflora incarnata, Valeriana officinalis, Piper methysticum, Withania somnifera, Crocus sativus, and Curcuma longa demonstrated anxiolytic, antidepressant, and sedative effects in clinical studies, with improvements in mood, stress levels, and sleep quality. Proposed mechanisms include modulation of monoaminergic and GABAergic pathways, serotonergic activity, regulation of the hypothalamic–pituitary–adrenal axis, and anti-inflammatory effects. However, clinically relevant risks were identified, including cytochrome P450–mediated drug interactions, excessive sedation, serotonin syndrome, and toxic effects associated with adulterated products, such as hepatotoxicity, cardiovascular events, and neurological disturbances. Conclusions: While plant-based supplements may provide clinically meaningful benefits for anxiety, depression, and insomnia, their use requires careful clinical monitoring due to potential pharmacokinetic and pharmacodynamic interactions and safety concerns. Increased awareness of herb–drug interactions and stricter quality control are essential to optimize therapeutic outcomes and minimize harm.