Zadok Paper S100 Winter 1999
The Nature of Humans-Mind and Brain; Body, Soul and Spirit
by Alan Gijspers

The paradox of addiction

What about drug addiction? Here the brain craves a chemical because that chemical stimulates the pleasure centre in the brain. The brain then develops a tolerance to the chemical, and needs more and more of the same chemical to get the same effect. One of the side effects is that the chemical also sedates the brain. The brain then develops stimulatory mechanisms to function optimally while under the influence of the drug. Sudden cessation of the drug will cause a withdrawal reaction which is an over-stimulation of the brain. This leads to an uncontrollable withdrawal syndrome of varying severity depending on the extent of the dependence.

This sounds terribly biochemical but currently the best accepted model of drug dependence recognises the interplay between psychological factors such as learnt behaviour, neurological factors such as neuro-adaptation and sociological factors such as peer pressure, drug culture, legal sanctions and so on (see diagram of the current WHO model of drug dependence15).

This is expressed more generally by the biopsychosocial model of human disease.16 Engel incorporates into his model the concept of emergent properties. This concept is taken from systems theory and states that in a hierarchy of systems a higher order has different properties which could not be inferred from analysis of lower orders. Thus actions at a neurological level could not have been inferred from the study of either isolated nerves or even neural networks. An example from architecture would be that you could not infer a cathedral from a stone or even from Gothic arches. Likewise, you cannot infer wetness from a single water molecule.

Engel's model implies an interplay between various levels of human function. Thus in his paper he describes a patient with a heart attack in which there are activities at the level of the individual cells of the heart to the boss's response to the patient's impending heart attack. He freely accepts both bottom-up and top-down causation attributing his hypothetical patient's final demise to the stress induced by a clumsy procedure.

Philosophers such as Nancey Murphy17 and David Chalmers18 use a similar concept to emergence called supervenience. However, they define it quite differently. For Chalmers the lower physical facts will determine the higher biological facts whereas for Murphey, quoting R.M. Hare, the biological facts, while influenced by the physical facts may change depending on context. In the former we are verging on classic determinism whereas in the latter we allow for top-down causality.

Whether we use emergence or supervenience, we accept that there are hierarchies of arrangements of ourselves and that we cannot fully understand who we are as humans by simply looking at one level. There are various levels of explanation, sometimes at the genetic and molecular level and sometimes at the much higher emotional and relational level. In clinical practice we spend most of our time moving (sometimes inconsistently) between the different levels according to what we regard as the most appropriate response to the clinical need.

Before looking in detail at the mind-brain debate we need to look at two other important aspects of humanity often forgotten in the mind-brain debate, but important if we think of body and soul, namely-the aspects of soul and spirit.

To: The soul and the spirit

Alan J. Gijsbers MBBS FRACP DTM&H PGDip Epi, is Specialist Physician at Turning Point Drug and Alcohol Centre and at the Department of Drug and Alcohol Studies St Vincent's Hospital. He is a Visiting Physician at the Epworth Hospital, a Senior Lecturer in Clinical Medicine at the Department of Psychological Medicine Monash University and Senior Fellow at St Vincent's Hospital Clinical School, University of Melbourne. He also contributes to a Dual Diagnosis Clinic at the St John of God and St Vincent's Collaborating Centre consulting on people with both Drug and Alcohol and Psychiatric Disorders. He is a fellow ISCAST and editor of their national bulletin. He also somehow manages to be a husband to his wife, Lois, and a father to three children.