Baseline characteristics of major depressive disorder patients in clinical trials in Europe and United States: is there a transatlantic difference?

Abstract

There is a widely spread belief that different patients are being recruited into antidepressant clinical trials conducted in Europe and the USA which is probably generated by the fact that recruitment strategies vary between the two continents. In order to get an insight into the patients’ characteristics in clinical studies on both continents, we compared the baseline characteristics of depressed patients in a database of a cancelled development program of an antidepressant (2220 patients, Intention-to-Treat group). For the evaluation of continental differences, we compared the elements of demographics, previous psychiatric history, DSM-III-R criteria, HAM-D and MADRS total scores and separate items and/or factors and CGI severity scores at baseline. USA patients had statistically significantly higher baseline values on height, weight and BMI. European patients showed statistically significantly higher baseline severity scores on HAM-D, MADRS and CGI. Furthermore, European patients had statistically significantly higher baseline scores on HAM-D factors I (‘anxiety/somatization’), VI (‘sleep disturbance’), and HAM-D Angst anxiety/agitation factor, whereas USA patients had a statistically significantly higher baseline value on the Bech depression factor and the HAM-D Angst retarded depression factor. European patients appear to have a more severe depressive episode with more anxiety and melancholic features. Some of the statistically significant differences found may be the result of a large sample size and are probably without any clinical relevance when the absolute size of the difference is taken into account. Our opinion is that the differences found in our sample between European and USA populations are much smaller than is generally expected and not of a magnitude that would question the reliability of the results obtained in our global world-wide, antidepressant drug development program. If our findings were reproducible in other antidepressant databases it would indicate that data gathered in Europe and the USA within a global antidepressant drug development can be pooled.