Epigenetic mechanisms are affected by several factors and processes including development in utero and in childhood, environmental chemicals, drugs and pharmaceuticals, aging, and diet. DNA methylation is what occurs when methyl groups, an epigenetic factor found in some dietary sources, can tag DNA and activate or repress genes. Histones are proteins around which DNA can wind for compaction and gene regulation. Histone modification occurs when the binding of epigenetic factors to histone “tails” alters the extent to which DNA is wrapped around histones and the availability of genes in the DNA to be activated. All of these factors and processes can have an effect on people’s health and influence their health possibly resulting in cancer, autoimmune disease, mental disorders, or diabetes among other illnesses. National Institutes of Health

Behavioral epigenetics is the field of study examining the role of epigenetics in shaping animal (including human) behaviour.^[1] It is an experimental science that seeks to explain how nurture shapes nature,^[2] where nature refers to biological heredity^[3] and nurture refers to virtually everything that occurs during the life-span (e.g., social-experience, diet and nutrition, and exposure to toxins).^[2] Behavioral epigenetics attempts to provide a framework for understanding how the expression of genes is influenced by experiences and the environment^[4] to produce individual differences in behaviour,^[5] cognition^[2] personality,^[6] and mental health.^[7][8]

Epigenetic gene regulation involves changes other than to the sequence of DNA and includes changes to histones (proteins around which DNA is wrapped) and DNA methylation.^[9] These epigenetic changes can influence the growth of neurons in the developing brain^[10] as well as modify activity of the neurons in the adult brain.^[11][12] Together, these epigenetic changes on neuron structure and function can have a marked influence on an organism’s behavior.^[1]