cases and controls.[37] However, given the cross-sectional design of the study, it is impossible to ascertain the temporality of the relationship between these methylation differences and depression. While it is plausible that these changes are involved in the etiology of depression, it is also possible that they may be the result of depression itself. In this way, the question of temporality between epigenetic modifications and pathology remains a substantial challenge to understanding the role of epigenetic modification in psychiatric disease.
