Erratum to: Eur J Epidemiol DOI 10.1007/s10654-017-0255-x

Figure 6 as originally published was incorrect—arrows were orientated from the risk factor to the confounder, whereas they should have been orientated from the confounder to the risk factor. This has now been corrected. The authors regret the error (Fig. 6).

Fig. 6
figure 6

Potential violations of the InSIDE assumption. Top panel pleiotropic effects act directly on the outcome (InSIDE satisfied); middle panel pleiotropic effects act on the outcome via single confounder (InSIDE violated); bottom panel pleiotropic effects act on the outcome via different confounders (InSIDE still violated). Arrows from the genetic variants to the risk factor may not be present for all variants; some variants may affect the confounder directly and not the risk factor. Notation: G 1, G 2, …, G J , genetic variants; X, risk factor; Y, outcome; U, confounder. Pleiotropic effects are signified by curved arrows