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The transmission of human experience from one generation to the next has occupied the minds of thinkers from Aristotle and Plato to Darwin and Freud and beyond. In recent years, genetics and epigenetics have figured into the explanation with increased prominence and nuance. Coined in 1942 by the British philosopher and biologist C. H. Waddington,
the term epigenetics refers to heritable changes in phenotype that—unlike those of genetics—do not involve alterations to the underlying DNA sequence. Epigenetics allows for events in the mother's or the father's life to be passed along to their offspring at a molecular genetic level. Recently, epigenetic research has moved into the realm of psychiatry to help account for the intergenerational transmission of traumatic experience. This new research has deep implications for psychoanalysis.
In a recent study published in the American Journal of Psychiatry, Yehuda and colleagues measured the distinct influences of maternal and paternal PTSD on psychiatric illness (phenotype), DNA methylation (epigenetics), and glucocorticoid sensitivity (proposed as a link between phenotype and epigenetics) in 80 adult offspring of Holocaust survivors and 15 demographically matched controls. Recognizing that increased glucocorticoid sensitivity confers greater susceptibility to anxiety and depression, the researchers hypothesized that inheritable patterns in DNA methylation would impact the glucocorticoid receptor in ways that would increase the rate of PTSD among adult offspring.
The investigators assessed psychiatric illness via the Structured Clinical Interview for DSM-IV (SCID) and psychometric tests administered by clinical psychologists for anxiety, depression, dissociation, relationship style, childhood trauma, and perceived emotional health. They calculated DNA methylation of the glucocorticoid receptor promoter gene by PCR amplification of 39 base pair sites in mononuclear cells obtained from morning blood samples. Finally, they per