Illness and disease do not necessarily run together. A patient may be reasonably well (no sickness), but if they feel unwell that's an illness. Similarly, patients with something physically wrong with them are diseased, but they may feel completely alright, they are not ill.
The biopsychosocial model presumes that it is important to handle the two together as they are both important. Proponents say that much money is wasted on healthy patients because the doctor is not treating the illness. From this perspective, a patient has not recovered from a disease until they feel better and their illness is over.
The biopsychosocial model gives great importance to the illness; therefore much more information needs to be gathered during a consultation. As well as the biological signs and symptoms, a doctor must find out about the patient's psychological state, their feelings and beliefs about the illness, and social factors such as their relationship with families and the larger community.
For this reason, the interview process should encourage the patient to give as much information about not only the physical symptoms, but how the illness affects the patient. This is a patient-centred approach, and generally involves open-ended questions designed for the patient to do much of the talking. The patient is also better involved in the treatment, and it includes steps to get over any illness as well as the disease.
As well as an separate existence of disease and illness, the biopsychosocial model states that the workings of the body can affect the mind, and the workings of the mind can affect the body.
This does not necessarily mean that there is a direct effect between mind and body, but that other intermediate factors can form a bridge from thought to biological fact.
Psychosocial factors can cause a biological effect by predisposing the patient to risk factors. An example is that depression by itself may not cause liver problems, but a depressed person may be more likely to have alcohol problems, thus liver damage. It is this increased risk-taking that leads to an increase likelihood of disease.
There are also theories that the state of mind directly affects the immune system, although most carefully-planned studies do not show this to be the case.
Of course, it is apparent to most people that a pathological disease can have an effect on a person's mind. It is not surprising that some people who have been diagnosed with cancer develop depression.
See Also: Activities of daily living