My understanding of health, and in particular, of how the physical, emotional and spiritual dimensions of the body connect, was revolutionised by The Book of Sufi Healing.  I found this in a local bookshop, and as soon as I picked it off the shelf, my heart started to hurt. A sign not to be ignored: without further ado I bought it. The book introduces the medicine system of Unani Tibb, established by Ibn Sina (Avicenna).
Modern Western science is drawing ever closer to the conclusions found in ancient and holistic medicinal knowledge: namely, that our emotions profoundly affect our body. Medical researchers currently say that the primary cause of heart disease is anger and stress. In medieval times, Europeans believed that the seat of our passions was located in the vital organs of the body. There follows a brief summary (taken from www.unani.com) explaining some of the basic concepts in the Unani Tibb system.
The Three Forces (Faculties) of the Body
We must distinguish between faculty and function. Faculties originate functions. A faculty is a power, a potentiality. The ultimate faculty is the soul, while the ultimate function is life. There are three natural faculties: the vital (baywaniat), the natural (taby’yat), and the psychic (nafsaniat).
There are two types of vital forces: the active and the acted upon. An active vital force would be one that causes the heart and arteries to dilate. The acted-upon vital forces are those that underlie anger, contempt, competition for victory, leadership, or fame, and other emotions. Thus, the emotional/psychological aspects of health and disease are considered holistically, as part of the entire person. For example, severe anger is believed to be the result of an excess of moisture in the heart humour, and its correction is accomplished with diet.
There are also two types of natural forces: those that serve other functions and those that are served by others. The natural forces that are served by other forces are three kinds: the generative, the growth-promoting, and the nutritive. The servant natural forces are four: the attractive, the retentive, the digestive, and the propulsive. These various forces interact intimately each with the other. The four servant forces serve the nutritive forces (by attracting, retaining, digesting, and propelling), and the nutritive force serves the growth-promoting force. The tint two forces serve the generative force.
The psychic forces perform three functions: (1) to mediate behaviour, (2) to cause voluntary movement, and (3) to create sensation. Within these functions are found the various events that serve imagination, create thinking, and underlie memory.
Now, the seat of each of these three forces has a point of origin: the natural forces arise in the liver; the vital forces arise in the heart; and the psychic forces arise in the brain. Over each of these natural forces is a corresponding spirit faculty, which serves as the nexus or interconnecting link with the non-manifest realms. That is, according to Avicenna, all life is dependent upon the divine permission (idbn) for life to begin and continue. The divine permission or cosmic force travels in through the indrawn breath and tint alights in the heart, where it is dispersed by the arteries throughout the whole body and activates both the natural forces and psychic forces.
– Umm Ilyas