There is also a need to integrate the vast and varied literature examining parental factors in the development of childhood anxiety and depression. Various reviews have attempted to do this, but are limited in a number of ways. Firstly, some reviews only include studies with a certain type of study design (e.g., cross-sectional only; McLeod et al., 2007a and McLeod et al., 2007b). This is mainly because there were too few studies with other designs (e.g., longitudinal) to include meaningfully in meta-analyses. Moreover, even when it is available, data from longitudinal studies are often difficult to extract for meta-analyses because of widely varying analytic approaches, including adjustments for different covariates (e.g. baseline symptoms, different socio-demographic measures) in analytic models.