Can Environmentally Induced Epigenetic Changes be Trans-Generationally Inherited by Offspring, Resulting in the Expression of Psychological, Behavioural, or Psychiatric Phenotypes? A Systematic Review

Background
Epigenetic modifications have been found to be associated with some psychiatric conditions. Environmental stressors can cause heritable changes to the epigenome. Thus there is a possibility that parental epigenotype could contribute to the expression of a psychiatric phenotype in offspring. Here we summarise and evaluate research about trans-generational epigenetic inheritance and its association with behavioural, psychological and psychiatric phenotypes.

Methods
Databases used included EMBASE <1947-Present>, Ovid MEDLINE(R) <1946 to September Week 1 2014> & PsycINFO <1806 to September Week 1 2014>. Studies were included if at least two generations were assayed on both epigenetic outcomes and behavioural/psychological/psychiatric outcomes. Given the limited available data, a meta-analysis was currently not appropriate.

Findings
Results were heterogeneous and there were many different outcomes. Generally behavioural alterations co-occurred with epigenetic modifications. There was some evidence of inheritance of both these outcomes between generations. Clinically relevant changes to gene expression levels and neuroanatomy were observed in several cases. Possible modes of epigenetic transmission from the experimentally exposed group to subsequent generations were implicated in some studies.

Conclusions
Despite the idea of epigenetics mediating trans-generational effects of the environment on brain and behaviour being widely touted, there is currently very little evidence. Moreover, mechanisms mediating such processes are unknown and thus whether epigenetic alterations induce behavioural change is currently still a matter of debate.

Author(s):

Rachel A Caddick^* and Anthony R Isles

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