Charaka Samhita, Sutrasthana 17.44
Sanchayah prakopashcha prasaro sthanam eva cha / Vyaktih bhedashcha shadete kriyakalah prakirtitah — Accumulation, aggravation, overflow, relocation, manifestation, and differentiation — these six are the action-times of disease development.

The six stages

Stage 1

Sanchaya — Accumulation

The Dosha increases in its own site (Vata in the colon, Pitta in the small intestine, Kapha in the stomach) without yet causing disease. The body signals this stage through subtle, vague symptoms: Vata Sanchaya produces a mild sense of fullness and discomfort in the lower abdomen; Pitta Sanchaya produces mild sourness in the stomach and slight yellowness; Kapha Sanchaya produces mild heaviness and loss of appetite. Most people dismiss these signals. Classical texts document Sanchaya as the optimal intervention point — the Dosha is still in its own seat and can be reduced with simple dietary and lifestyle correction.

Stage 2

Prakopa — Aggravation

The Dosha intensifies in its own site, producing stronger versions of Stage 1 signals. The body is still telling the person something is wrong through a single channel — but the signal is louder. Vata Prakopa: distinct abdominal distension, gas, constipation, restlessness. Pitta Prakopa: burning in stomach, hyperacidity, irritability. Kapha Prakopa: nausea, lethargy, heaviness, mucus production. At this stage, specific seasonal Panchakarma (Vamana in spring, Virechana in autumn, Basti in monsoon) is the classical intervention — the Dosha is still accessible in the primary channel.

Stage 3

Prasara — Overflow

The Dosha can no longer be contained in its primary site and begins to overflow into the general circulation (Rasa and Rakta Dhatu channels). This is the first stage where systemic symptoms appear. The person feels unwell in a generalised way — fatigue, loss of appetite, and vague body aches — but no specific disease has formed yet. Stage 3 is the last stage where relatively straightforward Shodhana (purification) can completely remove the Dosha before it settles in a vulnerable tissue.

Stage 4

Sthana Samshraya — Relocation

The overflowing Dosha meets a weak or compromised tissue (Khavaigunya — defective space) and begins to settle there. The site of future disease is being selected. This stage often goes unnoticed because the symptoms are still non-specific — a vague discomfort in the area where the disease will eventually manifest. The classical identification of Stage 4: dietary and seasonal factors that aggravate the specific Dosha produce discomfort specifically in the affected area, even before the disease is established.

Stage 5

Vyakti — Manifestation

The disease is now clinically established and recognisable. The specific Rupa (signs and symptoms) of the disease are present. This is the stage at which most people seek treatment — and it is the stage most commonly described in disease chapters because this is when the condition can be observed and named. Treatment at Stage 5 requires full Nidana Panchaka assessment and the complete classical treatment protocol — Shodhana followed by Shamana, with specific herbs and formulations for the condition.

Stage 6

Bheda — Differentiation

The established disease has developed complications and has differentiated into its specific type — with distinctive features that separate it from other conditions and mark it as a specific, chronic, often difficult-to-treat form. Charaka Samhita documents Bheda-stage conditions as the most challenging — tissue damage has occurred, secondary Dosha imbalances have developed, and multiple channels are affected. Treatment at Stage 6 requires long-term management rather than cure.

The intervention principle
The classical teaching: a disease identified and treated in Stage 1-2 requires no herbs — diet and routine correction is sufficient. Stage 3-4 requires Panchakarma. Stage 5 requires the full treatment protocol. Stage 6 requires management for life. This progression explains why Dinacharya and Ritucharya — the daily and seasonal practices that prevent Stage 1-2 accumulation — are the foundation of Ayurvedic preventive medicine. They are not wellness practices. They are Stage 1 intervention before Sanchaya develops into Prakopa.
Modern parallel — preventive medicine
The Shadkriya Kala model precisely describes what modern preventive medicine calls 'the natural history of disease' — from subclinical risk factors (Stage 1-2) through established disease (Stage 5) to complications (Stage 6). The difference: classical Ayurveda documented specific observable signs for each transition point, two millennia before modern epidemiology formalised the same concept without the individual-level observational detail.