Supplementary Material for: A Bibliometric Analysis of European versus USA Research in the Field of Addiction. Research on Alcohol, Narcotics, Prescription Drug Abuse, Tobacco and Steroids 2001-2011

<b><i>Background:</i></b> To compare the publication and citation rate within the areas of drug abuse and dependence research in Europe with that in the USA. <b><i>Methods:</i></b> This is a bibliometric study using the <i>Thomson Reuters Web of Knowledge</i> as data source, 40 key words were used as search terms, but certain scientific publications not concerning the issue were excluded. Scientific publications from Denmark, England, Finland, France, Germany, Italy, the Netherlands, Norway, Spain, Sweden, and the USA were studied. The number of publications in each country and in each year in addition to the citation indices for these publications was retrieved. <b><i>Results:</i></b> Approximately two thirds of the publications came from the USA. Both in absolute and relative figures, Europe lagged behind. The trend over the last decade was a greater gap between the amount of research performed in Europe versus the USA. There were thematic differences. Smaller European countries had a greater relative publication rate. The citations were relatively evenly distributed. <b><i>Conclusions:</i></b> It has been claimed that 85% of the world's research within the field of drug abuse and dependence is carried out in the USA. This study challenges this figure, but European research within this field is lagging behind.