Multivariate meta-analysis: modelling the heterogeneity mixing apples and oranges; dangerous or delicious?

Meta-analysis may be broadly defined as the quantitative review and synthesis of the results of related but independent studies. For the simple case where meta-analysis concerns only one outcome measure in each study, the statistical methods are well established now. However, in many practical situations there are several outcome measures presented in the individual studies included in a meta- analysis. In that case analyzing each outcome measure separately in a univariate manner is often suboptimal, and analyzing all outcome measures jointly using multivariate methods is indicated. For many situations with multivariate outcome, appropriate meta-analytic method