In probably the first allusion to publication bias, the British natural philosopher Robert Boyle said in 1661: “Many excellent notions or experiments are, by sober and modest men, suppressed.”1 Since then a large body of evidence has emerged to substantiate the existence of publication bias—that is, a tendency on the part of investigators or editors to fail to publish study results on the basis of the direction or strength of the study findings. Studies with negative or uncertain results are less likely to be published; even if they are, they take longer to appear than studies with positive results. Some investigators classify publication bias into three types: non-publication, abbreviated publication, and time-lag bias.2 In clinical medicine, publication bias usually comes to light as non-publication or delayed publication of trials that do not favour a new therapeutic intervention. This bias pervades all disciplines of science and medicine, including of course neurology. Although all areas in neurology are probably subject to this bias, the evidence for its …