that works for that individual.

If we lack any one of these three factors we will not develop that specific addictive outlet. For example:

If we do not have the genetic predisposition, then we will not become addicts of any kind. The Vietnam war veterans' study showed that most GIs who used addictive drugs during their tours of combat duty were able to get off them after returning home and were able to use alcohol, and perhaps other mood-altering substances, without progressive harm. They may have been physiologically addicted - developing withdrawal symptoms when the addictive substances were not available - but they were not spiritually addicted: they had no inner craving, driving them towards further use of mood-altering substances or processes. Ten per cent of the drug-using GIs, however, were not able to stay away from further addictive behaviour and were not able to use mood-altering substances such as alcohol sensibly. One has only to remember the young man playing Russian roulette in that beautiful film, The Deer Hunter, or the sea captain who lost both his legs in that other beautiful film, Forrest Gump, to see examples of combat veterans who were still trapped in the throes of active addiction.

The findings of the Vietnam War veterans' study are hotly disputed between the two opposing camps of psychological treatment:

1. Psychiatrists and others who believe that the study demonstrates that everybody could get off drugs but only some weak-willed or otherwise inadequate souls did not do so.
2. Those who believe that the study demonstrates that ten per cent of the population have a genetically inherited defect in neurotransmission whereas the rest do not.

It would be absolutely extraordinary if such a delicate and complex organ as the human brain did not provide examples of genetically inherited defects. After all, the liver, the kidneys, the adrenal glands, the thyroid glands, the pancreas and everything else in the body have genetically inherited defects, giving rise to particular clinical syndromes. The brain surely cannot have escaped this risk. We are aware of genetically inherited conditions - such as Down's syndrome - in which the mental facilities are impaired. It would be incredible if the mood centres of the brain were not to have corresponding examples of defective function.

Just because a particular condition is genetically inherited does not mean that it will necessarily be transmitted to all offspring. Other genes may have been inherited from the other parent or a particular condition may require a particular set of interactions between a number of genes, not all of which may have been inherited by a particular child.