Still searching for lost truths about the bitter sorrows of childhood.

A large proportion of children across the globe suffer abuse or neglect. Therefore, studies that shed light on the health consequences of adverse childhood experiences and examine the potential for resilience are of great importance. The meta-analysis by Varese et al. 3 in this volume is a welcome addition to these studies. Their meta-analysis addresses the question of whether childhood adversities are associated with risk of psycho-sis. Although a large number of studies have reported such an association, they have used a variety of research designs and a multitude of measures of childhood adversity and of psychosis. The meta-analysis brings together the many disparate strands of evidence that bear on this association. As the authors note, previous attempts to synthesize this literature have been " narrative reviews with inconsistent conclusions. " By contrast, their meta-analysis adopts a systematic and comprehensive approach. They took great care to collect results from as many sources as possible and to check for publication bias. Its results demonstrate a remarkable strength and consistency of evidence for some association " writ broad. " Thus, it demonstrates that we would be foolish to overlook the potential contribution of childhood adversity when we study the causes of psychoses. Nonetheless, we believe that the authors' conclusion— that there is a strong association between adverse childhood experiences prior to age 18 and risk of psychosis— is too strong. The susceptibility of these studies to bias, discussed below, poses a challenge to such a straightforward interpretation of the meta-analysis. The heteroge-neity of the studies introduces a further challenge. These challenges have to be directly confronted in order to make further progress in this field. Many readers might assume that the conclusion of a meta-analysis should be given much more weight than that of a narrative review. The uncertainties raised by particular studies appear to be overridden by the large numbers of individuals and of designs that can be included in a meta-analysis. However, this is not always true, 4 and the association between childhood adversity and psy-chosis provides an instructive example. The central problem in this field is that in almost all studies, the measure of childhood adversity is weak and is susceptible to bias that could create an artifactual association with psychosis. This is not a problem that can be solved by meta-analysis. Pulling together many studies that share a similar bias will produce a biased result. No matter how …