Genetic factors may predestine a person heavy smoking, drinking and drug-taking. This conclusion is drawn from a combination of 46 previous studies, positing an unambiguous link between two genes and the characteristics of persons with more dangerous lifestyles.

Analysis of data concerning 20 000 subjects revealed a possible link between a specific version of the gene 5HTT-LPR, which is involved in the transport of neurotransmitter serotonin and the tendency to develop an anxious, more neurotic personality. A second link was found between a gene for a receptor of neurotransmitter dopamine - the D4 receptor - and a more outgoing type. It was found that both conditions lead to increased tobacco, alcohol and drug abuse.

“Our study suggested the existence of a genetic basis for certain personality traits that may influence the behaviour of persons so as way as to make them, say, more inclined to smoke or drink” says Marcus Munafö from the Cancer Research Group in Oxford. “In future we should be able to prescribe made-to-measure pharmaceutical or behavioural treatments.”

Only these two genes displayed a strong correlation with behaviour. “Persons with a natural inclination to anxiety will also tend to smoke more”, says Munafö. “The average neurosis level of those with the short version of the serotonin transporter gene is 10 percent higher than normal” But he immediately adds: “The childhood environment and nutrition will also have a considerable influence on the way in which these genes find expression”

Variations in the dopamine D4 receptor gene may bring out the extravert side of a person by altering the response of the brain to the neurotransmitter. Dopamine is associated with a behaviour whereby we set off in search of fun and adventure, rendering us perhaps more inclined to experiment with new substances.

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