Depression is a mental health disorder which is categorized by mild to severe changes in mood and can affect physical, mental, and behavioural health. Recent evidence indicates that depressive disorders may represent an interactive matrix of reciprocally interactive pathophysiology influenced by various genetic and environmental factors. In individuals with genetic susceptibility, sustained stress can lead to deficits of the HPA axis, imbalanced monoamine/cytokines, decreased neurogenesis, and altered dynamics of connectivity in the reward and motivational circuitry. These mechanisms reduce neuroplasticity and impair the functional integrity of regulation neurocircuitry.

Therefore, preventive and therapeutic strategies have been considered to avoid and treat this disease. Drugs regulating neurotransmitters – including selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, tricyclics, and monoamine oxidase inhibitors – are the most commonly prescribed antidepressants. However, current antidepressants only have relative success and can induce side effects, particularly in chronic use. For these reasons, researchers have been searching for alternative therapeutic strategies, particularly involving the use of natural products.

This Special Issue aims to collect original research as well as review articles and meta-analysis addressing the use of traditional Chinese medicine formulas, Chinese herbs, and natural products as either extracts or isolated compounds in depression treatment. Therefore, we kindly invite researchers to contribute manuscripts with in vitro, in vivo, and clinical studies focusing not only on the effects of natural products on the control of neurotransmitters levels, but also on potential protection on connectivity in the reward and motivational circuitry.

Potential topics include but are not limited to the following:

• The similarity between depressive symptoms and the symptoms of emotional disease in traditional Chinese medicine theory
• Sources of traditional Chinese medicine formulas, Chinese herbs and natural products as either extracts or isolated compounds used in the treatment of depression
• Isolation and characterization of natural products useful in depression treatment
• Natural products in the regulation of the glutamatergic and opioidergic systems, maintaining homeostasis in depression
• Natural products with antioxidant and anti-inflammatory effects in depression
• Comparison of natural and synthetic drugs in depression treatment
• Chemical medications of natural products useful in depression treatment to improve their efficacy and/or safety