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Understanding the etiology of mental health impairment is currently undergoing a revolution, with advances in genomics and the knowledge that a convergent set of transdiagnostic liabilities account for the origins of disparate psychiatric syndromes. Such liabilities, collectively referred to as the "p-factor", reinforce theories of multifinality and early causal influence on enduring psychiatric syndromes. It is within this context that there exist new opportunities to more precisely identify which individuals in a population may be most vulnerable to adverse early experiences, and to clarify causal mechanisms underlying observed associations between adverse experiences and enduring behavioral outcomes. This is a systematic review of studies whose designs are adequate to address competing hypotheses of causation inferred by well-documented associations between maternal childhood trauma (MCT) and offspring behavioral outcome (OBO). Electronic databases were searched using a series of seven key words and phrases related to MCT and child behavioral outcome. This yielded a total of 506 articles, however only thirteen fulfilled the selection criteria for this review, by having study designs that were informative with respect to direction or mechanism of causation of the observed associations. These studies nevertheless comprised a total sample size of 30,188 mother-offspring dyads which are the focus of this report. Ultimately, genetic factors mediated a significant share of the association between MCT and OBO. In several studies, the genetic influences fully accounted for the association, suggesting formidable relationships between inherited liability and environmental exposure that are important to consider in social support of young families affected by MCT.