Epidemiological Evidence for Influences of Non-genetic Transgenerational Inheritance on Child and Adolescent Development

Our use of the term ‘Non-genetic transgenerational inheritance’ concerns the influence of environmental exposure to one generation on phenotypes in later generations in the absence of changes in the structure of the DNA. Although animal experiments have shown that the phenomenon exists in plants and animals, many scientists have expressed doubt as to whether this type of inheritance is detectable in humans. In this chapter, we describe the observational epidemiological data that has been published and evaluate the evidence for this type of inheritance. We mainly concentrate on the environmental exposures concerning famine, cigarette smoke and radiation, and chart the associations between pre-conception and prenatal exposures. We describe associations between these exposures and outcomes for the offspring and grandchildren. In general, we demonstrate frequent evidence of sex-specific differences in the likelihood of particular phenotypes, depending on whether it is the maternal or paternal ancestor who is exposed. We also show that the timing of the exposure is often important regarding specific outcomes, with particular emphasis on the 4-5 years before puberty for preconception exposures and the trimester of pregnancy for prenatal exposures. The evidence for non-genetic transgenerational inheritance is increasing. Interestingly, the consequences of exposures that are harmful to one generation often have a beneficial effect on a subsequent generation. It is important that future epidemiological studies are planned to collect information concerning previous and/or subsequent generations so that transgenerational consequences of exposures, such as medications or pesticides, can be charted.