Ayurveda: What is Disease?

Disease Causality (Trivida hetu):

There are three main causes for the disease i.e. – Asatmendriyaartha samyoga (Not using the five sense organs in the right way), Prajnaparadha (crimes against one’s own wisdom) and Parinama/ Kala (time/season). The Ati
yoga (excessive use), Ayoga (under use) and Mithyayoga (improper use) of these three factors are the main cause for all the diseases where as their Samyakyoga (proper use) leads to health. The first one is directly related to the indriyas/sense organs. Prajnaparadha is directly related to the mind and spirituality. Ayurveda clearly explains the bad deeds of manas/mind, kaya/body and vak/speech are come under prajnaparadha and should not be done in any condition. (not “just this little bit won’t hurt”) 

Unwholesome contacts/use of the sense objects is of 3 categories: underuse, overuse, and wrong use (trivida hetu). This is the cause of vitiation of the doshas.
Sa1#118-126

Unsuitable Use of the Senses:
Sense: Wrong Use/ Conjunction (yoga):

Sound – By hearing intense sound, no sound or too little sound, the auditory sense organ is destroyed. The contact of the organ of hearing with sound that is harsh, is fear causing, is inauspicious, is unpleasant, that coveys mishap is known as unwholesome contact.

Touch – The lack of touch, excessive or touch of the objects that are not to be touched, leads to diseases and disorders of the tactile sense organ. Untimely contact with micro organisms, spirits, poisonous gases and toxic winds, untimely contact of oily (ex. abhyanga when their is indigestion), untimely contact of cold, and untimely contact of hot substances is known as unwholesome contact.

Sight – By excessive gazing at brilliant objects, looking at very minute object, and not using the sight at all, the visual sense organ is damaged. Seeing that which is disliked, fierce, those sights that create fear, that which is tamasic, too distant, too near and too faint objects is known as unwholesome contact.

Taste – Excessive intake of one type of food or taste, avoidance of taste in utter disregard without thought, faulty intake, in respect of habitual suitability (i.e. what one has habit to eat may not cause disease because of habitual intake but this does not mean it is healthy for the individual and one good day it will have an effect) etc., eating poisonous foods, and little intake of food is harmful leads to the destruction of the sense organ of taste. Inadequate intake of the six tastes creates destruction of the gustatory faculty.

Smell – Inhaling too mild or too sharp odors or completely abstaining from use destroys olfactory sense organ. The contact with foul smelling, infested with micro organisms, poisonous, disliked smells, smell that produces disgust or aggravation, and also with those which are unseasonal.
Sa1#118-126

These are the three types of unwholesome contacts (atiyoga, hinayoga, mityayoga) with use of the senses to their respective objects (see above trividyahetu) that aggravate the doshas and create disease.
That which is not suited to the person (not following the rule of sahaatma or that which is not accompanying ones soul) is known as “asatmya” (unwholesome).
Sa1#127

The disease originated by the impairment of the senses known as “Aindriyaka” arises due to wrong, excessive and inadequate use of the sense faculties.
Sa1#128

Those 3 types of unwholesome contacts are responsible for all miseries (sukha). Balanced (samayoga) use (of time, intellect, and sense organs) brings heath but is very difficult to attain and is attainable through yoga only.
Sa1#129

Neither the sense organs nor the senses are the causes of happiness or unhappiness. They are only created by the 4 fold uses of senses i.e. proper utilization, insufficient use, overuse, and wrong use (it is all created by how you attach your senses). Even with the existence of sense organs and sense objects, there would be no disease, no misery, or happiness without the involvement (yoga) of the 4 fold uses of the senses. Therefore, these combinations are the causation for all happiness or unhappiness. (if there is no conjugation of the sense organs with any object, there is no sukha or dukha = yogas chitta vritti nirodhah)
Sa1#130-131

There can not be happiness or unhappiness without the soul, sense organs, mind, intellect, sense objects or the results of past karma. In the context of the science of medicine, only the four fold uses are at the causation of all happiness and miseries. The wholesome combination adherence is required while the unwholesome being given up is required for the maintenance of good health.
Sa1#132

There are the 2 ways of contact that give rise to happiness or misery, contact with the tactile sense organ and that of the emotions to the mind.
Sa1#133

Happiness (sukha) and unhappiness (dukha) are create desire (trsna) in the form of attraction (iccha) and aversion (dvesha). Desire is the primary cause of happiness and unhappiness. Pain (vedana), the sensations of happiness and misery, is the outcome of the contact of desire with the body and mind. If there is no contact, sukha and dukha do not exist. 
Sa1#134-135