Last updated at 10:00 AM on 11th October 2011
Young people who love drinking coffee are more likely to get hooked on drugs, scientists have claimed.
A new study found those who respond favourably to caffeine, also found in energy drinks, could predict how they responded to other stimulant drugs such as amphetamines and cocaine.
Not everyone who enjoys caffeine will abuse cocaine, they added, but they say there is a clear vulnerability to the effects of these drugs.
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The finding published in Drug and Alcohol Dependence is based on a study of 22 people who were asked if they preferred caffeine to a placebo tablet. They were then given a type of amphetamine and asked to rate it.
Most who liked the caffeine liked the drugs.
Professor Stacey Sigmon, of Vermont University in the United States, said: 'People differ dramatically in how they respond to drugs.
'For example, a single dose of a drug can produce completely opposite effects in two people with one absolutely loving and the other hating the drug's effects.
'It is important to improve our understanding of these differences, as they may reflect key individual differences in vulnerability or resilience for drug abuse.'
The scientists believe that a person's response to the d-amphetamine also reveals how they would react of other commonly-abused drugs like cocaine as they have similar effects.
UVM Associate Professor Dr Stacey Sigmon, conducted the first study to find a response to caffeine could predict the positive effects of another drug on a volunteer
The study is the first to demonstrate caffeine prospectively predicts the positive subjective effects of another drug.
Professor Sigmon said: 'While these data do not mean that every coffee lover is at risk for proceeding to cocaine abuse this study does show individuals vary markedly in their subjective and behavioural response to psychomotor stimulants, and those for whom a modest caffeine dose serves as a reinforcer are the same folks who subsequently report more positive subjective effects of d-amphetamine.'