- Etiology (Cause of a disease): In Ayurveda several Sanskrit words like hetu, nimitta, karta, karana, yoni and mula are used in place of ‘nidana’ (etiology) as synonyms for the cause. Inappropriate food habits, lifestyle and other external factors that cause disequilibrium (increase/decrease) in dosas (Vata, Pitta and Kapha), dhatus (plasma, blood and others), malas (fecal matter, urine and other malas) and mental attributes – rajas (action or passion) and tamas (ignorance or inertia) – are the internal causes that result in endogenous diseases and external factors such as poison, weapons, fire, microbes, trauma and so on are the external causes (which do not vitiate the dosas and dhatus) that results in exogenous diseases. These reasons or causes are termed ‘nidana’ (etiology). These causes are divided into four categories.
- Sannikrsta Karana (Precipitating causes): These are the factors responsible for the sudden aggravation of the dosas without the stage of accumulation. It also hastens the process of disease evolution, e.g., exposure to the cold produces a severe cold suddenly.
- Viprakrsta Karana (Causes of longer duration or distant causes): Dosas accumulate in the body over a period of time and subsequently produces disease. In such conditions, the cause may be present but the expression of disease takes a longer time. For example, frequent travelling, irregular eating habits and exposure to cold are all responsible for vata vitiation over a period of time.
- Vyabhicari Karana (Feeble causes): These are the weak causes, unable to produce the disease but act as a carrier. When a favorable situation arises for the manifestation of disease, the disease arises. They are not the direct causes of the disease.They do not produce a disease unless their strength is increased by certain favorable factors such as a stressful environment, incompatible diet and a dosa aggravating lifestyle, which does not produce disease immediately but with a favorable environment like nature of locality, time, combination, potency and quality, they result in outburst of disease.
- Pradhanika Karana (Fulminating causes): These are the causes which react instantly and produce disease quickly, e.g., toxins, poisons and accidents.These causes are again divided into two groups.
* Exogenous factors: This includes unfavourable food habits, lifestyle and seasonal adaptability.
* Endogenous factors: These factors provoke the dosas and dhatus (tissues) towards disequilibrium, resulting in disease development.
Etiology or the specific causes of the diseases also include:
(1) Intellectual blasphemy (Prajnaparadha): The intentional violation of socio-religious
code of conduct. It may lead to indisposition, impairment or misuse of intellect or mental
activities, patience, composure and memory, which further results in undesirable activities wherein one gets struck in stress, depression and other stress-related psycho-somatic disorders. Such persons are the victims of intellectual blasphemy. In this condition all the three types of dosas are aggravated.
(2) Incompatibility of sense organs: This is caused by the connection of the senses with unfavorable and incompatible subjects, which include all those actions that are considered to be the cause of overuse, underuse and misuse of the eyes and other sense organs with their subjects.
(3) Unfavorable season and time: Seasons also time periods are important. If in a specific season adverse climatic conditions occur, then that season is considered to be unfavorable. For example, excessive heat in summer or extreme cold in winter or heavy rain in the monsoon are the extremities of the season. If the effect of these conditions is less in certain seasons, then it is a moderation of the season. If in a certain season opposite conditions are produced (like rain in winter, cold in summer) then it is called an altered state of season. When a person faces unfavorable seasons and harsh conditions, he may become victimized by many diseases.
(ii) Premonitory signs and symptoms: When accumulated dosas get aggravated due to different reasons, this leads to vitiation in the dhatus (tissues of the body), agni (digestive fire) and srotas (channels), which will naturally produce a disease. For the manifestation of disease, dosas have to pass through many levels before the actual onset of the disease (This will be described under the stages of disease manifestation).
In this sequence, accumulated and aggravated dosa spread throughout the body and ultimately localize at a specific place. In this condition, during accumulation at a specific location, some premonitary symptoms develop. On this basis, a physician infers about the disease that will evolve. These signs are preliminary or premonitory signs and symptoms. For example, preliminary signs of fever are fatigue, discomfort, change in skin and complexion, lacrimation, pain and heaviness in the body, yawning, anorexia, cold, blackouts, tasteless tongue and so on. These signs indicate the emergence of fever. There are two types of premonitory symptoms:
- Generalized symptoms: Those preliminary signs that inform only about the general nature of a disease are called generalized preliminary signs. For example, fatigue is a preliminary sign of fever.
- Specific symptoms: Those preliminary signs that give definite and exact information about the nature of disease are called specific preliminary symptoms.
(iii) Manifest signs and symptoms: Symptoms that indicate the actual onset of the manifestation process, indicate the specific features of a disease and also vitiated dosas and condition of ama are rupa (sign or symptom). In Ayurveda, this is also known by other terms such as linga, cinha, laksana and so on. When disease becomes more pronounced and is at its peak, specific and clearly defined symptoms appear. For example, raised temperature in fever, watery stool in diarrhea, coughing in bronchitis.