A lot of people have been sick this year. Maybe you’ve been lucky, but I’m sure you know someone who has been hit with the seasonal cold/flu. If it seems like it’s getting worse, you’re right! This year has seen many more illnesses in the clinic. My experience is mirrored by that of my friends in the Western medical world, as well. So, what’s going on? It’s true that America has a health crisis. (The rates of diabetes and heart disease are higher than they should be, and most of us could stand to exercise more). Certainly, this doesn’t make for a strong immune system. However, I think an arguably more important cause (and very under-recognized) is the weather – the very world we live in. Abnormal weather creates abnormal health; it’s harder for the body to be in balance and harmony with the environment, when the environment changes unpredictably. This is also recognized in the research community, take, for example, the following statement from The Royal Society Publishing, “One important area for future research is the effect of disrupted seasonality on the dynamics of infectious disease. A recent review has highlighted the unprecedented rate at which vector-borne diseases have changed over the past decade, and has alerted a wide audience to the impact of changes in the climate .” (Stevenson, 1). This is clearly the perspective of Classical Medicine, where irregularities of the weather are attributed to the rise of epidemics, lingering pathogens, and even stress and damage to specific organ systems. Let’s take some time to explore this bummer of a topic, what it means for you personally, and realistic ways to stay healthy through the seasons.
The weather and epidemics
Before exploring thoughts on epidemics, let’s define a very important term, Qi(氣). This is important to clarify at the outset, because it is often mistranslated and confused in English, especially in a medical context. It does not mean “energy” in general, as many people believe. A more accurate definition of Qi is:
- air, gaseous movement, vapor, atmosphere
In this sense, it is important to emphasize the semantic flavor of “influence”, “bearing”, or “gaseous movement”. This is important in understanding the effect of weather on health when we look at such classical statements as:
"There are (times when a given season) has not yet arrived, but it's qi arrives; when (a given season) arrives, but the previous season's qi fails to leave; (and when a given season) arrives and (its qi is) excessive." Jin Gui Yao Lui 1.8金匱要略 (Wiseman, Wilms, 16)
What this statement is saying is that there is both a qualitative and quantitative aspect to a season. Furthermore, these two aspects must be in accordance with one another for a given organism to be able to harmoniously respond to and interact with its environment. There has to be a cyclic predictability. There are many ways to look at this, but, the clearest example is to say that the qualitative aspect is the weather (temperature, humidity, barometric pressure, wind, cloud cover, etc.), whereas, the quantitative aspect is the latitude of the sun in the sky (quantifying time).
Examples of this are everywhere. Mammalian reproduction is often triggered by hours of daylight, which is determined by the sun’s latitude. Growth and fruiting of plants is determined by the percentages of blue vs. red light of the sun, and dormancy and starch storage is determined by the number of hours. Again, all are products of latitude. Additionally, we see changes to phenotype relating to weather and sun. For example, fat deposition and storage, winter vs. summer coats in temperate environment animals, and dry vs. oily skin in people. These are just some of the profound changes that are triggered by seasonal change.
Now, what happens when an organism is triggered by a change in daylight, but there is not the appropriate change in season (or vice versa)? Or, what if seasons change to quickly, or reverse? Invariably, that organism is put under severe stress, and this stress manifests as sickness.
For example, trees may flower too early, before pollinating insects have awakened in the spring - or, they may flower and be killed by a later frost. Animals may give birth in times that are too cold, when they lack the fat stores to both live through the scarcity of early spring, and produce milk for their young. Or, unseasonable warm spells may give rise to early and excessive occurrences of pathogenic bacteria, viruses, or parasites, while the animal is still in a stressed and weakened state.
The discord between the quality and quantity of season – i.e. the imbalance between the season and its Qi (氣) – encourages a specific, broad-scale pathogenic state, which represents a severe, specific and atypical disease transmission and progression. This pathogenic state, tied to a specific period of time, is called “Pestilential Qi” (癘氣), and was first described by Wú Yòu kě (吴又可 1582 - 1652) in the early 1600s. Pestilential Qi is defined as:
- transmitted person-to-person
- acting as a toxin
- entering through the mouth or nose
- not immediately manifesting of symptoms
You will probably recognize this as looking suspiciously like modern germ theory, and accurately describing the transmission of disease in an epidemic.
A hallmark of Pestilential Qi (癘氣) is that it is sudden, severe, and seasonal. Take, for example, the sudden die-off of more than half of the Saigas Antelope population last winter. ( http://www.nytimes.com/2015/11/03/science/more-than-half-entire-species-of-saigas-gone-in-mysterious-die-off.html?_r=2 ). Scientist’s theory is that “Climate change and stormy spring weather … may have transformed harmless bacteria carried by the antelopes, called saigas, into lethal pathogens.” Of note is that the die-off was severe, lasted less than a month, and ended in May, when the season changed.
Scientists described the occurrence as “mysterious”. However, the actual event is entirely clear and predictable from a Classical Chinese Medicine point of view. The only mystery – what the actual pathogen was – is of little consequence, considering that in all probability the pathogen was benign, and the real fault was the triggering event – the weather. From this perspective, the quoted statement is not correct. Harmless bacteria did not suddenly become lethal. Rather, irregular weather weakened the immunity of the animal to the extent that it was no longer able to be in balance with its environment (in this case, balance as represented as the ability of the immune system to hold a pathogen in check).
Now, remember, you’re an animal too. So, all of these things we see happening in nature are happening in you, even if modern comforts cause us to forget that. (In fact, sometimes, modern comforts may be more of a problem, as they make it even harder to adjust to the “actual” environment, as in “Air conditioner sickness”). For example, in recent history, we see SARS and MERS. Going back just a little further, we have mass epidemics and pandemics (consider the Spanish Flu of 1918, which incidentally started in the spring, and would flare the following winter – in correlation with seasonal change). This year, we just so happen to have seen a lot more (and worse) cold and flu in the unseasonably warm months of November and December.
So, to recap, a large part of staying healthy is avoiding abnormal stress. This is quite hard to do, and may in fact be unavoidable, if the main source of stress happens to be a rapidly changing environment.
The concept of Lingering (or Lurking) Pathogens is more complicated, as it charts disease progression and change over a longer period of time. The original description of this condition comes from one of the founding books of Chinese Medical theory, the “Huang Di Nei Jing” (黃帝內經), or “The Inner Canon of the Yellow Emperor”, written between 475 BCE – 220 CE, where it states:
If (a person) is harmed in winter by “cold”, he will (suffer from) warmth disease in the spring.
If he is harmed by “wind” in the spring, he will develop outflow of (undigested) food (vomiting/diarrhea) in the summer.
If he is harmed in summer by “summer-heat”, he will suffer from emaciation and malaria in autumn. (alternating chills/fever and episodic flu-like symptoms)
If he is harmed in autumn by “dampness” (excessive mucus), he will develop a cough in winter. (Unschuld, 195)
A more direct way of stating this is: “The cold of winter causes a recurrence of illness in spring; the wind of spring makes people unable to retain food in the summer; the heat of summer causes intermittent fever in fall; humidity in fall causes a cough in winter.” (Marcus, 29)
Noted Sinologist and Medical Historian Paul Unschuld clarifies the experience of the Ancient Chinese in stating, “Winter is the season of cold, spring is the season of wind, summer is the season of heat, and autumn is the season of dampness. Presumably, the human organism was considered vulnerable to the excessive impact of seasonal Qi, and man was forced to prevent this impact through appropriate measures”. (Unschuld, 195).
Specifically in regards to our current winter season, the Huang Di Nei Jing states that the conditions for Lingering Pathogens occur when a person has a Jing (精) or “essence” deficiency, and is exposed to pathogenic influence in the winter. Essentially, what this means is that, whether through congenital weakness, old age, or immoderate lifestyle (overwork, under/over-exercise, poor diet), a person’s “core vitality” becomes weak, and this weakness allows a winter pathogen to enter the body without resistance.
It’s very important to note here, that even though a person gets sick in the winter, in this scenario, they manifest no symptoms at the time. Rather, sickness erupts in a following season. So, the pathogen enters both with no resistance, and with no immediate evidence. This concept was further developed by Wang Shu-He, (famous 3rd century physician), in his observation, “If a disease occurs immediately after exposure to cold, it is caused by cold. However, the cold does not (necessarily) bring out the disease [immediately]; rather, it can lurk in the skin and muscles. A warm disease will occur if the cold emerges in the spring. A summer-heat disease will occur if the cold emerges in the summer.” (Liu, 8)
Expanding on this, Zhu Yi-Zhong (c. 1108) proposed the now accepted theory that Lingering Pathogens may dwell in the body, but require a triggering event to be expressed. This event is most commonly exposure to a secondary pathogen, but may also be stress brought on by extreme emotional taxation, overwork, or dietary irregularity – especially overconsumption of sweet/sugary foods and alcohol. The explanation behind this is that a cold pathogen enters in the winter, where it lurks in the interior. Even though it entered as cold, due to its effect on body systems, it brews a low-grade, internal heat (immune and inflammatory response). This heat is not great enough to show on the surface, i.e. there is no fever, irritability, thirst, etc. However, when exposed to a secondary stress, the body’s anti-pathogenic response mingles, aggravates and intensifies the internal heat to erupt in sudden, possibly severe symptoms.
This is quite a fascinating concept, because in some ways it mirrors our modern understanding of incubation periods of specific types of pathogens. While this is certainly not the entirety of the concept, nor where physicians at the time thinking in terms of infectious agents, such as bacteria or viruses, it is nonetheless interesting to note that they did observe the body’s tendency to hold on to (and later express) a pathogenic influence, especially if the body is weak and vulnerable.
So, what might this look like? It can look like sudden sore throat after a warm spell in the spring. It can look like everyone in the family getting a mild cold, while you get a high fever. Or, it can look like emotional stress followed by vague, flu-like symptoms. Interestingly, classic texts make mention of Lingering Pathogens created through incorrect treatment, as well. In our modern world, we may see this in such examples of allergies after a course of antibiotics (or itching and hives), or chronic diarrhea after anesthesia, etc.
The important point to make here is that this Lingering Pathogen can only be created if the body is weak and susceptible to opportunistic invasion. Here, we see the connection between weather as an environmental stress/trigger and the strength of the body’s immune response (as influenced by our personal choices of diet and lifestyle) in the dynamic of disease response and susceptibility. Therefore, how we take care of ourselves in the moment is incredibly influential in how we get sick in the future.
The Weather’s Effect on Organ Systems
Now that we’ve discussed the general effect of weather on health in terms of Pestilential Qi (癘氣), communicable diseases, and Lingering Pathogens, let’s get a little more personal and look at the effect of weather on the specific organ systems of the body and explore this effect as a causative factor in disease. Before doing so, however, let’s first define what an organ system is.
One of the main points of confusion, which makes dialogue between Western and Chinese Medicine difficult, is one of clearly defined terminology. The aforementioned Qi (氣) is certainly a problem. Equally problematic is the definition of an organ. Rather than viewing the organ strictly as a solid viscera, or material thing, the classical perspective of an organ is one of a “functional category”; a category detailing the intersection of physiological function, energetic function, mental and emotional bearing, and correspondences to the external environment.
From this perspective, we can more easily see how the body’s internal environment relates to, and is influenced by, the external environment, in other words, the relationship of the microcosm to the macrocosm. Furthermore, within this system of correspondence, there is an observable relationship between an organ and a particular body tissue, sensory organ, season, taste, and direction, etc.
What we are most concerned with in this paper is an organ’s relationship to a season (and by extension, direction). However, it adds validity to our discussion to point out that there is a clear relationship between taste, pharmacology, and organ function, because it makes clear that these correspondences are far from arbitrary. This taste relationship is based upon molecular structure – similar molecular structures will exert a similar effect upon various organ functions of the body, and due to their similar structures, they will have a similar taste. The most obvious example of this is any type of sugar; it tastes sweet and affects the pancreas. Bitter flavors are generally caused by structures that are antibiotic and anti-inflammatory, such as berberine. (This is why people complain of bitter mouth after taking antibiotics). This flavor also tends to depress an over-active nervous system and slow heart rate. Therefore, it is said to have an affinity for the heart.
Before I digress too far, let’s return to the relationship of the organs to the seasons.
Let’s look first at the kidney. In classical Chinese Medicine, the (functional category of the) kidney is seen to be the storehouse of the body’s fundamental/core vitality. This is expressed as body temperature (the ability to heat and maintain life) and core energy (as opposed to food-derived energy). Being a storehouse, it both stores and conserves vital energy, while also being a reservoir the body draws from. In this way, it mirrors aspects of the adrenal glands. As such, the kidneys need periods of rest and recharge, both daily and seasonally, or they will become overtaxed and drained. The season that encourages storage is winter. Therefore, winter relates to the kidneys insofar as it both mirrors and helps them complete their function.
This storing function can be seen everywhere around us right now, for example, in animal hibernation, winter fat stores, dry skin (less blood at the surface of the body), and starch storage in plant roots, etc. We tend to eat more and exercise less. Our muscles tighten and skin dries as blood and heat move inward. We sleep more (or at least want to). We have less energy, and are prone to seasonal affective disorder, and on and on, all in an effort to stay warm and conserve energy. The direction of storage, then, is inward and consolidating.
This seasonal change is vital to the organism that is adapted to it (even though we complain about it ALL winter long), and is a natural rhythm of energy storage and expenditure, much like sleep/wake cycles. Parallels of this observation are recognized in Western Medicine, as well. Take, for example, the following statement on seasonal change and immunity in animals:
In many species, tissue function is reprogrammed between subjective winter and summer states, generating endogenous rhythms that approximate a year (i.e. circannual rhythms) [3,6–9]. The existence of innate circannual rhythmicity has been demonstrated when organisms, from unicells to vertebrates, are maintained in constant environmental conditions for many years [6–11]. Species with genetically programmed annual rhythmicity occur globally, from high latitudes to the equator, and even in apparently ‘constant’ environments such as the deep sea . Genetic programming is seen to be adaptive because it is pre-emptive and serves to predict and prepare organisms for alternations in seasonal environmental conditions [12–14]. (Stevenson, 2)
So, what happens when winter isn’t winter? Or, what happens if we don’t behave like it is winter? Probably the clearest example of this is to look at what happens to plants. In order to germinate, many seeds need a prolonged period of cold before a gradual warming in the spring. This then perfectly sums up the directionality of both winter and spring. Winter is a time of inward consolidation and storage, followed by spring, which is a time of outward expansion and expenditure. Of importance here, is that without the prolonged cold of winter (the consolidation and storage) there is no energy for subsequent expansion in the spring.
So, if the winter is too warm to trigger the storing function of the body, or, if we don’t act in alignment with winter and overtax ourselves instead of storing, what happens to the kidneys? Naturally, one would assume that the kidneys would be stressed. This is most certainly true. However, just like the example of seed germination, the effects aren’t recognized until the following season. So, we have a hidden damage to the organ of winter, but the expression of that damage in the organ of spring.
The organ of spring is the liver and is related to outward expansion. This outward expansion is seen in many aspects of an organism, including; increasing physiological function and energy expenditure after a period of dormancy; the rise of sex hormones needed for reproduction, triggered by increasing temp and sun; increased hours of wakefulness; and changes of vasculature at the surface of the body allowing greater blood flow, heat venting, and sweat/oil production, to name just a few.
Returning to the “Huang Di Nei Jing” (黃帝內經), we have the statement that “opposing the Qi” of winter harms the kidneys, and in the spring “causes limpness with receding [qi]”. Again, we’re faced with the problematic translation of Qi. However, if we look at the context of the statement, the meaning becomes clearer: if one acts out of synch with the weather of the season, or, if the weather itself is out of synch with the season, the kidneys can’t store and recharge, the organism doesn’t “reset”, and subsequent states of increased physiological function are compromised. The result is limpness (muscle atrophy, tightness, weakness, and possibly even paralysis or stroke), and “receding [qi]” (fatigue) in the spring.
Now, if we consider that the Chinese organ is a system of correspondences, including emotional and psychological content, we would also expect to see a measureable change in the psychology and emotional response correlated with the liver. The emotion associated with liver pathology is anger/depression. Therefore, in this case, we would expect to see a higher degree of aggression in the spring. This simultaneous pathology of both physiology and psychology is, in fact, exactly what we see:
“Seasonal human morbidity is observed in non-infectious diseases, including heart disease , cerebrovascular disease  and lung cancer . Behaviour-driven mortality is also seasonal; cycles in the monthly numbers of suicides are one of the oldest and most replicated findings, with most, but not all, studies finding a peak in late spring/early summer (figure 2a). Interestingly, aggression and other violent acts such as homicide have a marked seasonal pattern of occurrence nearly coincident with that found for suicide (figure 2b). Seasonal patterns in aggression are not limited to the individual level. Historical records indicate a strong rhythm in population-level forms of aggression measured in onset of battles.” (Stevenson, 2)
So, as you can see, not only does seasonal change affect overall immunity, with increasing susceptibility to infectious disease, it puts a stress and strain on very specific organ systems at clearly defined times, with higher incidences of specific physiological and psychological disease. In the next section, we’ll talk about traditional strategies to adjust to the seasons and help prevent this stress of seasonal change.
Strategies for adjusting to the seasons
Wisdom about staying healthy in a given season can be found in many different places. A lot of it is common sense. Some comes from old sayings – bits of old-timey wisdom captured in linguistic amber. Some comes from modern research. Some comes in the form of arcane texts recording generations of human experience in strange (only to the modern reader!) metaphor.
Let’s use the arcane as our platform for understanding which ways of living allow us to be in balance with the seasons, and to be able to adjust as gracefully as possible. As we do so, a proper understanding of context, terminology, and theory will reveal that these arcane statements are actually not esoteric at all, but rather quite straightforward and grounded in real, direct observation.
From the “Huang Di Nei Jing” (黃帝內經) on winter:
The three months of winter, They denote securing and storing. The water is frozen and the earth breaks open.
Do not disturb the yang [qi]. (陽氣) Go to rest early and rise late. You must wait for the sun to shine.
Let the mind enter a state as if hidden [as if shut in] As if you had no secret intentions; As if you had already made gains.
Avoid cold and seek warmth and Do not [allow sweat] to flow away through the skin. This would cause the qi to be carried away quickly.
This is correspondence with the qi (氣)of winter and It is the Way of nourishing storage. Opposing it harms the kidneys.
In spring this causes limpness with receding [qi] (氣), and There is little to support generation. (Unschuld, Tessenow, 49-50)
So, what does this mean? Well, this statement actually makes a great deal of sense. In the winter it’s cold out. This cold represents “securing and “storing” as everything enters a period of hibernation or reduced activity. Living in harmony with the season, then, reflects a mode of living that supports this storing process. For example, the statement “Go to rest early and rise late” is fairly obvious.
However, in order to really understand the passage, let’s define the term Yang. Yang (陽) is a somewhat difficult term to translate, which denotes qualities of “heat”, “motion”, “light”, “something exposed” etc. Yang only makes sense when contrasted against its opposite, yin (陰), which denotes qualities of “cold”, “stillness”, “darkness”, “something hidden”. Yang and yin can only be defined in relationship to one another.
Applied to our topic, the season of winter is yin. Therefore, to act in a way that is yang (to disturb the yang qi) is to go against the season. So the statement, “Do not disturb the yang [qi]”, while somewhat esoteric, starts to make more sense. It becomes clearer still when taken in the context of the later line, “Do not [allow sweat] to flow away through the skin.” If winter is the time of storage, body heat and vitality should be at the core. The process of sweating vents heat to the exterior. This heat is the yang qi of the body (it’s core vitality), which we are warned not to disturb during this season. This venting of heat has two effects:
- It “opens” the exterior, and allows external cold to enter. In other words, the body undergoes a pathogenic response to external pressures, resulting in symptoms of cold/flu, aches, pains, etc.
- In venting heat to the surface, it leaves the core cold and empty. This insecurity of the core of the body readily lends itself to digestive issues, fatigue, and further opportunity for pathology down the road.
The following lines comment on the mental bearing one should have during this season:
Let the mind enter a state as if hidden [as if shut in] As if you had no secret intentions; As if you had already made gains. (Unschuld, Tessenow, 49)
Essentially, what it’s saying here is hunker down, stay inside, and don’t exhaust yourself with “planning and scheming”. Or, as stated in a previous chapter, do “not tax [yourself] with meaningless work.” (Unschuld, Tessenow, 31).
So, what does this mean practically? Well, if we understand that pathology in the winter involves weakness at the exterior and coldness at the core, naturally, our goal would be to prevent this from happening by doing the exact opposite, i.e. preventing heat from escaping the exterior and preventing cold from entering the interior.
To prevent heat from venting through the exterior, we would want to avoid activities that specifically promote an active sweat. These include intense cardiovascular exercise and hot bathes/saunas. This is especially true if any of these activities take place outside. A person with a strong constitution may be able to sweat with less consequence, but even so, you should make sure you’ve stopped sweating and that your external body temperature has returned to normal, before going outside. Instead of cardio, one should focus on muscle building activities that get the heart rate up. Baths are ok, however, you should take care that they are not too hot, and/or you don’t spend too much time in them. Saunas, in general, are only good for the very robust, or for those that live in VERY cold climates (as their exteriors are generally much tighter/secure – believe it or not, Wisconsin is not that cold).
To prevent cold from entering the interior, we need to pay attention to what we eat and drink, and take care not to eat cold foods. For starters, ice water is obviously cold. Not only does this directly cool you down from the inside out, it also causes the stomach to spasm and empty its contents into the small intestine prematurely, thus taxing and weakening the system. Cold food, likewise, is hard on the digestion. In addition to foods that are thermally cold, foods can be energetically cold. Energetically cold foods are foods that require more energy (enzymes, bile, or stomach acid) to break down, or foods that are high in certain types of fibers (ex. raw vegetables), sugars (ex. beans), etc. which disrupt the balance of our gut micro-biome, and cause symptoms of digestive weakness.
In the winter, your body is focused on maintaining vital core heat, in the face of continual loss of heat at the surface. This means there is simply less energy in the digestive system at this time, and less energy to go around in general. Furthermore, greater energy expenditure on foods that are not calorically dense is counter to the “storing and securing” function of the body in winter. So, it’s a metaphorical double-whammy.
Therefore, to prevent cold from entering the interior, you should make sure the majority of your food is cooked. If you’re a salad eater (whether because you love it, or you feel guilty) pay attention to how you feel afterward. Do you feel gassy and bloated? Lightly cooked vegetables, with an emphasis on more calorically dense macronutrient choices, such as healthy fats and lean protein will make you feel much better in this season. Not only that, they will give you a better shot at being healthy when spring comes, when you should be eating more seasonally fresh greens and salads. Lastly, in the winter, one should also supplement the diet with warming spices, such as ginger, fennel, anise, curry, cinnamon, etc. These will help to warm and move the digestion and prevent the buildup of those turbid substances a weak digestion will create, (such as phlegm/mucus, diarrhea, oily skin, etc.)
Now that we’ve talked about what you should do, let’s talk about the likely effects that may happen if you don’t. If one over-sweats in the winter, one can easily experience tight and achy muscles, headaches, runny nose, and frequent seasonal cold/flu. If one habitually eats cold foods, one can expect an increase in gas, bloating, diarrhea, lack of appetite, and possibly nausea. If one habitually does both, they’re pretty much done for! They’re more than likely going to get sick – if not this winter, then next spring.
Lastly, it’s always a good idea to come in to the clinic. Believe it or not, Chinese Herbology excels at infectious disease and the treatment of the common cold and flu. Not only that, but it can get you back on track to make sure you stop getting sick in the future. Acupuncture is very effective for similar presentations, and will quickly help with the aches and pains of cold, tight muscles. Finally, even though the weather is becoming more unpredictable, the human animal is not. We can anticipate the changes that you will be facing in the near term (based on how the environment interacts with your personal constitution), and we can help to make the seasonal transition a smooth one.
So, there you have it. You are right to think seasonal illnesses are becoming more severe and more frequent, and in many cases it’s caused by the environment we all take for granted. This changing environment we live in affects us in profound ways, both physically and mentally. However, with the understanding and perspective of classical Chinese medicine, we can both anticipate those changes in the future, and make proactive, positive changes in our lives in the present, so we can be as in balance and healthy as possible.
Stevenson TJ et al. 2015 Disrupted seasonal biology impacts health, food security and ecosystems. Proc. R. Soc. B 282: 20151453. http://dx.doi.org/10.1098/rspb.2015.1453
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Unschuld, P. U. (2003). Huang Di nei jing su wen: Nature, knowledge, imagery in an ancient Chinese medical text, with an appendix, the doctrine of the five periods and six qi in the Huang Di nei jing su wen. Berkeley: University of California Press.
Marcus, A. (2004). Foundations for integrative musculoskeletal medicine: An east-west approach. Berkeley, CA: North Atlantic Books.
Liu, G. (2001). Warm diseases: A clinical guide. Seattle: Eastland Press.
Unschuld, P. U., Tessenow, H., & Zheng, J. (2011). Huang di nei jing su wen: An annotated translation of Huang Di's Inner Classic -- Basic Questions. Berkeley: University of California Press.