See Nidana panchakam.
Ayurveda classifies all disorders in terms of qualitative changes. The twenty qualities gunas) are manifest in the doshas, dhatus, urine, feces and sweat, and they affect the mind and consciousness. In fact they are present throughout the universe. Our body is constantly exposed to the outer environment, which induces its qualities into the body, mind and consciousness through diet, lifestyle, seasonal changes and the quality of our relationships. These qualities slowly create changes in the doshas, which result in an increase of the particular doshas that share those attributes.
In order to face a cold environment, the bodily intelligence creates a craving to eat hot soup with pepper or to drink hot coffee with ginger. This craving is created by the doshas, which try to balance the qualities in the environment. If vata is increased, it creates a craving for something soft and warm, such as porridge with milk or ghee. That will calm down vata dosha.
On the other hand, aggravated doshas can also create perverted cravings. If the doshas are in the early stages of samprapti they create healthy cravings, but after a while they cause wrong cravings that further aggravate that dosha. Similarly, if there is ama (toxicity), the cell membranes become clogged with toxins and this disturbs cellular intelligence, resulting in poor communication.
Ama means undigested, unprocessed and not utilized food particles, which create metabolic wastes that circulate in rasa dhatu (plasma). Ama also creates wrong kinds of cravings that should not be satisfied.