The theory of emotion and will refers to the seven emotions (Qi Qing: happiness, anger, worry, thinking, sorrow, fear, and fright) and five wills (Wu Zhi: happiness, anger, thinking, sorrow, and fear) [1] . Hereby, “will” means normal emotional activities and “emotion” means hyperactive activities. In Chinese medicine, emotion-will plays a basic role in the onset, progress, and prognosis of almost all diseases, not only the psychological and psychiatric disorders. The emotion-will overcoming therapy (EWOT) derived from the philosophical foundation of Chinese medicine, i.e. Yin and Yang, and five elements, is believed to be the most effective modality in dealing with mental illness.

For thousands years, medical experts have been exploring the importance of emotion-will and efficacy of EWOT in medical records since the establishment of Chinese medicine theoretic and therapeutic structure in Yellow Emperor’s Inner Classic (Huang Di Nei Jing) [2] . At present, Chinese medicine practitioners still frequently utilize EWOT in treating depression, anxiety, phobia, etc. and nursing chronic diseases such as apoplexy sequelae, cancer, diabetes, irritable bowel movement and so on [3] -[6] . From the 1980s on, Chinese researchers have been trying to translate this emotion-will with very Chinese characteristic in conventional psychological language. Some promising results have been made. For instance, relationships and similarities among EWOT and cognitive and behavior therapy (CBT) [7] , positive psychology therapy [8] , and Morita therapy (MT) [9] [10] have been discussed. But, regrettably the emotion-will system and EWOT have not been introduced to the Chinese medicine practitioners and psychology therapists outside China except for rare literature with rough description [11] [12] . Comparing with the prosperous spread of acupuncture and herbal medicine, two major therapy approaches in Chinese medicine, EWOT is, however, a brand-new option and promising method dealing with mental illness [4] [13] [14] . This essay covers the origin and development, underlying mechanism, clinical application, basic researches of emotion-ill system and EWOT and the comparison with conventional therapies.

Records on emotion-will date back to The Book of Rites (Li Ji, 51-21 A.D.), in which happiness, anger, sorrow, fear, love, hate, and desire, the seven emotional reactions human beings have [15] . It is in Yellow Emperor’s Inner Classic that the theoretic foundation is established. This book elaborates the relationship between emotion-will and organs, the pathogenesis of illness resulting from extreme emotions, and the treatment of emotional disorders, leading to a sound foundation for the development of the emotion-will theory.

The relationship is constructed on the model of five organ and five wills and emotions linked by the five elements theory, that are, liver-anger, heart-happiness, lungs-grief, spleen-pensiveness, kidneys-fear (Figure 1).

This principle is considered as the foundation of emotion-will therapy in the treatment of emotional disorders and mental illnesses followed by later Chinese medicine practitioners supplementing and developing it. There are three representative advancements. First, Dr. Wuze Chen (1131-1189 A.D.) clarified the seven emotions, i.e. Qi Qing: happiness, anger, worry, thinking, sorrow, fear, and fright and differentiated the connotations of the Seven Emotions and five wills. Second, Congzheng Zhang (1156-1228 A.D.) recorded plenty of medical cases covering the utilization of EWOT in treating emotion-will disorders. Third, Wan Su Liu innovated a new understanding of extreme emotions, that is, a hyperactive emotion which gives rise to internal fire and accordingly injuries the related organ. In the 1980s, Prof. Miqu Wang and his peers believed in the modernization and systematization of the emotion-will theory. Thus Chinese medicine psychology (CMP), a new discipline, emerged, which bases on the philosophic essences of Chinese medicine and borrows the structure from current conventional psychology [16] . Still, in Chinese medicine psychology EWOT is a major approach.

EWOT is regarded as a major clinical non-drug intervention in Chinese medicine psychology. For thousands years, a large amount of medical cases have been kept. Wang et al. [17] analyzed 196 ancient cases of disorders induced by seven emotion and found that EWOT was the most commonly applied approach. Yang et al. [18] analyzed 122 cases and found similar results as Wang’s report. Meanwhile, other Chinese medicine psychology therapies were also applied such as suggestion therapy, stimulation therapy, behavior conduction therapy, etc., which were less frequently used than EWOT. Liu [19] (2009) treated 12 college students suffering phobia only with the technique of POF, resulting in satisfactory outcome. Clinically, EWOT is not only used to treat emotional disorders or mental illness, but also to treat and nurse other diseases e.g. menopause syndrome, irritable bowel syndrome, cardiovascular illnesses [20] -[22] . Ye et al. [23] found EWOT could alleviate anxiety and depression of stroke patients and enhanced their enthusiasm and initiative to take part in rehabilitation. Chen [24] reported a positive role EWOT played in the treatment of asthma, supported by the improved quality of life.

Current researches on the foundation are concentrated upon the sorting and editing ancient literature and experiments on the exploration of how the seven emotions impairs organ. Liu et al. [25] found the experimental evidence that prenatal fear derived from earthquake mimic could cause developmental insufficiency manifested as slower growth and poorer behavior performances. The finding is a convincing support for the understanding of EWOT. Zhang et al. [26] found that maternal fear negatively affected physical and nervous system development of the fetus, with specific alterations in neuro-hormones and gene expression. Interestingly, JKSQW (Jin Kui Shen Qi Wan) a preventative Chinese herbal formula reduced these negative outcomes which proved that the kidneys’ function was disturbed by fear from another angel. Although plenty of clinical reports on EWOT are available, unfortunately, there are no reports available on fundamental researches of the underlying mechanism of the five techniques in EWOT.

EWOT plays an essential role in Chinese medicine psychology. It has a distinctive feature of Chinese culture. Recently, researchers have paid attention to the comparative study for it with conventional western psychology therapies. Yan et al. [27] found the application of EWOT in the treatment of emotional disorders and mental illnesses was in accordance with some therapies in conventional psychology, for instance, supportive therapy, behavior therapy, cognitive therapy, etc. Huang [8] believed that the technique HOS is pretty similar to positive psychology created by Martin E. P. Seligam. Positive psychology interventions (PPIs) is a promising approach to increase happiness and well-being, that is, treatment methods or intentional activities that aim to cultivate positive feelings, behaviors, or cognitions [28] . With intervention of HOS, approaches making a patient happier e.g. joyful music, conversation, favorite foods, reading and so on are employed to overcome the sorrow the patient encounters. Clinical cases on the treatment of depression and anxiety have been frequently reported [18] [29] . Sufficient evidence shows that PPI is an effective approach to treat depression, anxiety, and other psychological and psychiatric illness [30] [31] .

Chen et al. [10] believed EWOT might share the same cultural origin with Morita Therapy and the skills of the two systems were similar. But differences existed between the procedures and appetencies. Morita therapy was regarded as the extension of EWOT in Chinese medicine psychology. The goals of Morita therapy are the recognition of facts, obedience to nature, focus on the present, the increase of spontaneous activities, the decrease of self-focused preoccupation, the elimination of indulgence in moods and emotions, the withholding of value judgments, the reduction of intellectualizing, the cessation of escape into a sick role, and the cultivation of a humble mind [32] [33] . The goal deeply rooted in Chinese Buddhism, Taoism and Confucianism [34] .

Researchers compared EWOT with behavior therapy. Similarities were found in theoretic foundation and intervention intention, but the procedures, general protocol, and appetency were different [7] [12] . Taking HOS as example, behaviors such as jumping, dancing, howling, playing drum produce joyful emotion, which can decrease the disorders resulting from extreme sorrow or sadness. HOS is very similar with the positive reinforcement in behavior therapy. Positive reinforcement is applied to encourage and reward normal behaviors thus to suppress and replace bad behaviors [35] .

In conclusion, EWOT is a unique therapeutic approach based on the emotion-will theory in Chinese medicine. Even though the conventional psychological modalities hold predominant status in China, it still requires localized adjustment to become more suitable for Chinese people. Although greatly influenced by western models, contemporary Chinese approaches to counseling reflect the philosophical traditions, cultural history, and indigenous help-seeking practices of a rapid modernizing society [36] . EWOT, rooted in Chinese culture and philosophy, ought to be more suitable without too big obstacles. Owing to the advantages of demanding simple environment, few disturbances, convenience, and compatibility with other Chinese medicine approaches, esp. acupuncture, EWOT is believed to have a promising prosperity and high value in dealing with psychological illness [37] . Disadvantages are unavoidable. Systemic therapeutic protocol has not been established. Lack of standards and effective evaluations remain a primary obstacle impeding the popularization and developing of EWOT. Our team and colleagues are trying to eliminate the obstacles in the following aspects: 1) designing rational trails and experiments to validate the efficacy and provide evidence for clinical use; 2) standardizing operation protocols; 3) developing assessment tools; 4) introducing EWOT abroad and studying it from cross-cultural perspective. We have strong faith in the bright future of this ancient, but new psychological therapy.

This study was under the support of National Science Funds of China (NSFC) with the Grant No. 81373710 and Science and Technology Development Fund of Chengdu University of TCM with the Grant No. (ZRMS-201348).

The authors declare no conflict of interests.