Environment is a broad term that can include things like nutrition, exposure to toxins, education, housing. family and social relationships, and so forth.

When any experience is perceived as threatening, either because of external threats or because of internal, imagined threats or anxiety, the same physiological processes are activated.

Chronic or traumatic stress can alter DNA patterns via the process we just described.

It’s called methylation because methyl molecules are chemically added to a DNA sequence, most often causing the gene activity to turn off.

Methylation is one of the best understood epigenetic process and it’s been studied extensively in genes related to the stress and immune systems. When genes are methylated, they are ‘read’ differently and generally suppress gene activity.

A final thing to note is that these chemical modifications to gene activity, produced by environmental exposure, tend to persist and can be inherited by offspring.