turn is likely to predict the viability of brain tissue. This imposes considerable limitations to internal validity. On a similar note, the time-horizon of epigenetic changes is unclear—it is possible, therefore, that epigenetic changes that may not induce concomitant changes in gene expression may yet influence gene expression at a later point in the life course. In that regard, studies should consider the downstream influences of epigenetic change on gene expression and psychopathology at multiple points in the life course in order to strengthen causal inference.
