A look at what can happen to our brain if we become addicted and a discussion of the long term effects.
Brian is an alcoholic on a journey to find out why he became an addict.
Brian's social experiences are very different to that of his sister, Ann. Could that be a reason for his addiction?
Brian and Ann are assessed by psychologists to see whether addicts have different thought processes to non-addicts.
How scientists are studying genetics to try to track down the 'addiction' gene.