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We used a genetic variant that increases cigarette consumption amongst smokers to investigate whether the positive association between smoking and caffeine consumption is likely to be due to smoking causing greater coffee/tea consumption. We investigated this relationship in three studies from the UK (UK Biobank), Denmark (the Copenhagen General Population Study) and Norway (the HUNT study). Each additional copy of the smoking increasing variant was associated with consuming 0.1 additional cups of coffee per day amongst smokers, but not amongst never smokers. Evidence for an association with tea consumption was weaker. These results suggest that smoking increases coffee (and perhaps also tea) consumption. This may be due to smoking increasing caffeine metabolism or a behavioural link between smoking and coffee/tea drinking.