Content analysis of the summaries of scientific articles containing “ADHD” and “D4” or “DRD4”.

*Human studies were divided into articles providing data on the DRD4 gene (“data”) or not (“citation”).
The presence of the following statements was numbered.
1) “DRD4 associated with ADHD”. In these articles, the association of the DRD4 gene with ADHD is stated as an established fact.
2) “DRD4 gene is associated but it confers small risk”. In these articles the first statement is mitigated by either mentioning raw data (e.g. odds ratio) or by stating that the DRD4 gene confers small risk to ADHD.
3) “DRD4 is not associated with ADHD”. These articles defend the view that the association of ADHD with the DRD4 gene does not reach statistical significance.
4) “Not relevant”. In these articles the summary was not informative enough to know whether the authors defend the view that the DRD4 gene is associated with ADHD.