The main limitations of the present study were the cross-sectional design, neither allowing any causal interpretation nor clear assessment of temporal sequences as suggested by Saunders’ model. Although the GP’s refusal rate of 56.4 % was considerable, as other studies with register-based random sampling usually have lower response rates [51, 52] it seems overall acceptable. As reported above, the majority of GPs refused study participation for reasons unrelated to this study. However, some GPs reported doubts about releasing patient data despite approval from research ethics boards and assurance of full anonymity and very few GPs were afraid of losing patients given the nature of the study on patients’ alcohol use which is a stigmatized subject [9]. Therefore it cannot be excluded completely that those GPs who refused study participation have a different patient population than the participants of this study. Furthermore, due to the low response rate in the open ended questions we can only speculate about those who did not give any reasons. While we could not find any patient characteristics predictive of reporting a reason for not seeking
