The central nervous system (CNS) is a part of the nervous system that is divided into parts consisting of the brain and the spinal cord. The primary function of the CNS is to process the information received from the peripheral nervous system. Important neuroanatomical features of the CNS include neurons, glial cells, axons, membranes, and the neural tube and the ventricular system. Emotionality is also among the various activities integrated by the CNS through the activity of different neurons and neurotransmitters. However, some situations can unbalance neural circuits and cause mood disorders, also known as mood affective disorders. The mood disorder is a group of conditions of mental and behavioural disorder, where a disturbance in the person's mood is the main underlying feature. These disorders fall into seven groups, including abnormally elevated mood, such as mania or hypomania. Moreover, depressed mood is best-known and most researched as major depressive disorder (MDD) (alternatively known as clinical depression, unipolar depression, or major depression). Additionally, moods which cycle between mania and depression, known as bipolar disorder (BD) (formerly known as manic depression).

The presently available drugs for the treatment of mood disorders are symptomatic only, produce adverse reactions, and some unresponsive patients. Therefore, there is a high demand for the discovery of novel therapies to treat mood disorders. There is an urgent need for novel effective treatments, and many new research strategies are centred on traditional medicine as an alternative or complementary solution. There have been many experimental and clinical studies emerging during the last decade looking to investigate the potential application of herbal products, mainly medicinal, to prevent or treat these disorders when used either as complementary or alternative treatments. The results of such studies have reinforced the importance of herbal preparations for the development of new drugs to treat such disorders and have shown their adjuvant role in enhancing the effectiveness of the approved treatment in progress. However, despite popular use, different plant species still lack scientific contributions to validate their use.

The aim of this Special Issue is to bring together original research and review articles discussing the use of medicinal plants based in folk medicine to treat mood disorders. This Special Issue aims to highlight research that can contribute to the improvement and innovation of clinical practice within psychiatry.

Potential topics include but are not limited to the following:

• • Non-clinical and clinical studies regarding the potential role of plant extracts used in folk medicine to treat major depressive disorder
• • Non-clinical and clinical studies regarding the potential role of plant extracts used in folk medicine to prevent or treat mania and anxiety, and associated-psychological disorders
• • Non-clinical and clinical studies regarding the potential role of plant extracts used in folk medicine to treat major bipolar disorder
• • Investigations concerning isolated compounds from natural sources to prevent or treat mood disorders
• • Safety of plant extracts or isolated active compounds used for the management of mood disorders