TCM etiology (bing yin 病因) describes how disease arises — not through the language of pathogens and pathology that biomedicine uses, but through the interaction between the body’s functional capacity (Zheng Qi 正氣, “righteous Qi”) and the factors that disrupt it. Disease occurs when disruptive factors overwhelm the body’s capacity to maintain balance. Whether a person becomes ill depends not only on the strength of the disruptive factor but on the state of the body that encounters it.
This principle — that disease reflects the interaction between challenge and resilience, not the challenge alone — parallels the biopsychosocial model and the insight from pain science that symptoms reflect the state of the processing system, not just the magnitude of the input.
The six external causes (Liu Yin)
The six external causes (liu yin 六淫, “six excesses”) are environmental factors that can invade the body from the outside. They are named after climatic phenomena but describe functional qualities of pathogenic influence, not weather conditions per se:
Wind (feng 風) — the pathogen of change and movement. Wind attacks suddenly, moves rapidly, and changes quickly. It attacks the upper body and the surface first. Wind rarely appears alone — it combines with other pathogens (Wind-Cold, Wind-Heat, Wind-Dampness) and is often called the “spearhead of disease” because it opens the door for other pathogens. Clinically: sudden onset symptoms that migrate (wandering joint pain, itching that moves around), tremors, dizziness, facial paralysis. Biomedical correlates include acute upper respiratory infections and some neurological presentations.
Cold (han 寒) — the pathogen of contraction and slowing. Cold constricts and contracts: it tightens muscles, slows circulation, congeals fluids, and obstructs Qi flow. Cold produces sharp, fixed pain (contraction restricts flow, and where no flow, there is pain). Clinically: chills, aversion to cold, clear copious secretions, pale tongue, tight or slow pulse. Cold contracts the body surface, closing pores and blocking sweating — trapping the pathogen inside.
Heat/Fire (re/huo 熱/火) — the pathogen of excess activity and consumption. Heat flares upward, consumes fluids, agitates the mind, and accelerates processes. It produces inflammation, redness, swelling, and thirst. Clinically: fever, red face, thirst for cold drinks, dark concentrated urine, constipation, rapid pulse, red tongue with yellow coating. Severe heat can disturb Shen — producing delirium, confusion, or agitation.
Dampness (shi 濕) — the pathogen of heaviness and stagnation. Dampness is heavy, turbid, sticky, and difficult to resolve. It obstructs Qi flow through sheer viscosity rather than constriction. Dampness tends to settle in the lower body and impair the Spleen’s transformative function (the Spleen governs fluid transformation; Dampness overwhelms it). Clinically: heaviness in the head and limbs, aching joints worse in damp weather, poor appetite, nausea, loose stools, thick greasy tongue coating, slippery pulse. Dampness combines readily with Heat (Damp-Heat) or Cold (Cold-Damp), and these combined patterns are common and clinically important.
Dryness (zao 燥) — the pathogen of depletion and desiccation. Dryness depletes body fluids and damages Yin. It primarily affects the Lung (which governs moisture distribution and is the most externally exposed Yin organ). Clinically: dry cough, dry throat, dry nose, dry skin, dry stools. Dryness is most common in autumn (Metal phase, Lung season) and in arid environments.
Summer Heat (shu 暑) — the pathogen of summer, always external. It combines heat and dampness: profuse sweating, thirst, heaviness, possible nausea or diarrhea. Summer Heat is the only external pathogen that is seasonal by definition — it occurs only in summer.
External causes and biomedical concepts
The six external causes are not the same as biomedical pathogens (viruses, bacteria, allergens), though they often describe the same clinical events. A “Wind-Cold invasion” describes the functional pattern of what biomedicine calls an upper respiratory viral infection: sudden onset, chills, body aches, nasal congestion, headache. But the TCM description emphasizes the body’s functional response to the invasion (contraction, obstruction, cold predominating) rather than the identity of the pathogen. Two patients with the same virus may present different TCM patterns — one Wind-Cold, one Wind-Heat — because their bodies respond differently.
The seven emotions (Qi Qing)
The seven emotions (qi qing 七情) are internal causes of disease: joy, anger, worry, pensiveness, sadness, fear, and fright. In TCM, emotions are not separate from physiology — they are activities of the organ-function systems. Each emotion is associated with a specific Zang organ:
| Emotion | Organ | Effect on Qi | Pathological pattern |
|---|---|---|---|
| Joy (xi 喜) | Heart | Slows and scatters Qi | Excess: mania, scattered attention, inappropriate laughter |
| Anger (nu 怒) | Liver | Makes Qi rise | Liver Qi stagnation → Liver Fire: headaches, red face, outbursts |
| Worry (you 憂) | Lung | Knots and depletes Qi | Chest tightness, shallow breathing, fatigue |
| Pensiveness (si 思) | Spleen | Knots Qi | Poor appetite, bloating, fatigue, rumination |
| Sadness (bei 悲) | Lung | Dissolves Qi | Shortness of breath, weak voice, pale complexion |
| Fear (kong 恐) | Kidney | Makes Qi descend | Low back weakness, urinary incontinence, loss of control |
| Fright (jing 驚) | Heart/Kidney | Scatters Qi | Palpitations, insomnia, anxiety, hypervigilance |
The critical insight: emotions become pathogenic not when they occur but when they are excessive, prolonged, or suppressed. Anger is a normal, healthy response. Chronic suppressed anger that produces years of Liver Qi stagnation is pathogenic. Grief is an appropriate response to loss. Prolonged, unresolved grief that depletes Lung Qi produces chronic fatigue, immune vulnerability, and respiratory weakness.
This framework connects directly to psychology and particularly to the concept of defense mechanisms. TCM’s description of how suppressed emotions produce physical symptoms through their effects on specific organ-function systems parallels the psychodynamic concept of somatization — psychological distress expressing itself through the body. The vocabulary differs; the clinical observation is remarkably similar.
Emotions and somatics
TCM’s understanding of emotional-somatic connection also parallels somatic approaches. The Liver governs sinews and tendons; chronic anger produces muscular tension, particularly in the neck, shoulders, and jaw. The Kidney governs the bones and low back; chronic fear produces lumbar weakness and tightness. These are the same patterns that somatic education identifies as “sensory-motor amnesia” — habitual muscular contractions that have become unconscious, maintained by unresolved emotional states.
The connection is not coincidental. The body does not distinguish between “physical” and “emotional” tension. The musculoskeletal patterns that Thomas Hanna called the “red light reflex” (chronic flexion from fear/withdrawal) and the “green light reflex” (chronic extension from effort/urgency) correspond to the functional states TCM assigns to Kidney (fear) and Liver (drive/frustration).
Other causes
Beyond external and emotional causes, TCM identifies several additional pathogenic factors:
Diet: irregular eating habits, excessive consumption of specific tastes or temperatures, and food that the Spleen cannot transform all produce disease. Excess raw and cold food weakens Spleen Yang. Excess greasy food produces Dampness and Phlegm. Excess sweet food produces Dampness. Alcohol produces Damp-Heat in the Liver and Gallbladder. The TCM dietary framework is not about calories or macronutrients but about how specific foods affect the body’s functional balance — their thermal nature (hot, warm, neutral, cool, cold), their taste (each taste has a functional effect), and their effect on specific organ systems.
Overwork, excessive rest, and excessive sexual activity: overwork depletes Qi and Jing; excessive rest stagnates Qi; excessive sexual activity depletes Kidney Jing. These are causes of disease because they disrupt the body’s dynamic balance between activity and conservation.
Phlegm (tan 痰): both a pathological product and a cause of further disease. Phlegm is a pathological accumulation of fluids that the Spleen has failed to transform. It can be visible (sputum, nasal discharge) or invisible (producing nodules, masses, numbness, or mental confusion — “Phlegm misting the Heart”). The saying “the Spleen is the source of Phlegm; the Lung is the storehouse of Phlegm” reflects how Spleen dysfunction produces the Phlegm that then manifests in the Lung as respiratory symptoms.
Blood stasis (xue yu 血瘀): blood that has stopped flowing and accumulated. It produces fixed, sharp, stabbing pain; dark complexion; varicose veins; masses; and a purple tongue with dark spots. Blood stasis can result from Qi stagnation (Qi moves Blood; when Qi stagnates, Blood follows), trauma, cold (which congeals Blood), or heat (which can damage vessels and cause extravasation).
Pathological progression
Disease in TCM is not static. It progresses through predictable patterns:
Exterior to interior: an external pathogenic factor (Wind-Cold, Wind-Heat) first attacks the body surface. If not resolved, it penetrates deeper — from the Tai Yang stage to the Yang Ming, then to the Shao Yang, and so on through the Six Stages, or from the Wei level to the Qi, Ying, and Xue levels through the Four Levels. Each stage of penetration involves different organ systems and requires different treatment.
Excess to deficiency: acute disease often begins as an excess pattern (pathogenic factor present, body fighting vigorously) but can progress to deficiency if the body’s resources are exhausted by prolonged fighting. A strong fever (excess Heat) that burns for days can damage Yin (fluids, cooling substance), producing a deficiency pattern after the acute phase resolves.
Cold to heat, heat to cold: Cold patterns can transform to Heat if the body’s Yang response generates excess warmth, or if the Cold condenses and produces stagnation that converts to Heat. Heat patterns can damage Yang over time, eventually producing Cold. These transformations explain why the same illness can present differently at different stages.
Along Five Phase relationships: dysfunction propagates through the generative and controlling cycles. Liver Qi stagnation (Wood) overacts on the Spleen (Earth), producing digestive symptoms. Chronic Spleen deficiency (Earth) fails to generate adequate Lung Qi (Metal), producing respiratory and immune weakness. The Five Phases predict these trajectories.
Understanding pathological progression allows the practitioner to anticipate where a disease is heading and intervene preventively — treating not just the current pattern but the pattern that is likely to develop next.
Related
- Pattern Diagnosis — how the causes identified here are organized into diagnostic patterns
- Zang-Fu — the organ-function systems affected by pathogenic factors
- Five Phases — the relational framework through which disease propagates
- Three Treasures — the layers of vitality that pathogenic factors can disrupt
- Psychology — the seven emotions as internal causes of disease
- Somatics — the body-emotion connection in somatic practice
- Traditional Chinese Medicine — the medical tradition that uses this etiological framework