Memes are information encoded in the brain that can be disseminated and replicated.  Memory, in the form of connections of neural clusters forming long-term potentiation (LTP), is the fundamental building block of memes.

Perception of sensory stimuli is compared with pre-existing neural connections in the association cortices (memes), resulting in a stress or salutary interpretation.  LTP and meme-formation occurs when the resulting perception is affectively laden.  Meme-mediated stress-response may cause local methylation of certain genes (e.g., glucocorticoid receptor expression in hippocampus), deactivating them.  Nurturing memes may cause acetylation and thus reactivate the genes.  Such meme-instigated activation/deactivation of specific genes during early childhood may determine the vulnerability of individuals to stress in later life.  For example, the serotonin transporter promoter gene short allele (5HTTLPR s/s) has been shown to interact with childhood abuse and later stress in the risk of depression and suicidality.  Studies of migrants show that those with vulnerabilities are likely to develop major psychiatric illness when migration is seen as stressful, and the symptoms of the psychiatric illnesses reflect cultural memes prior to migration.  In spite of the presence of severe stress, social support has been shown to reduce the risk of posttraumatic stress disorder and other conditions. 

Why certain individuals, and not others, develop the disorders may depend on epigenesis, memes introduced early in life, and meme-processing.  Memes may be manipulated through techniques such as relaxation. Memes as replicators may augment the effect of a stressful event as the stressful event is repeatedly replicated in the media.  Social support may neutralize the replicating stress memes through propagation of nurturing memes from the social network.

Environment affects genes through memes, the neural connections representing memory of a sensory event. Memes that entered the brain in early life have a lasting effect, together with epigenesis, in future vulnerability to stress and pathogenesis.  As replicators, stress memes may be self-augmenting, but may be attenuated by nurturing memes of social support. Longevity may represent a happy combination of salutary genes and salutary memes.