Abstract
Leo Sher, Rockville, MD, USA:
Dani Rowland-Klein and Rosemary Dunlop did an excellent job describing the transmission of trauma across generations and the psychological state of children of Holocaust survivors [1]. I would like to offer some comments on their paper.
It has long been recognised that behavioural traits run in families. In 1621, Robert Burton wrote in his book The Anatomy of Melancholy that the ‘inbred cause of melancholy is our temperature, in whole or part, which we receive from our parents’ [2]. Evidence from contemporary twin, family and adoption studies and molecular genetic research supports the Burton's point of view that behaviour has a firm genetic basis. Behavioural genetic research has shown that there is a very considerable genetic component to normal personality traits, cognitive abilities and psychopathology [3–9]. Some behavioural disorders may have a larger genetic component than medical diseases, such as hypertension or ischemic heart disease [3].
Between 30 and 60% of the variance in many personality traits is inherited [3]. In the ‘Minnesota Study’ on measures of interests, skills and personality traits, the identical twins reared apart had correlations between 34 and 78% [4]. Fraternal twins studied by the same researchers had correlations between 7 and 39% [5]. It has been found in studies of young twins that fearfulness (behavioural inhibition) and shyness are heritable [6]. An interaction between the dopamine D4 receptor gene and the serotonin 2C receptor gene has a substantial effect on the trait of reward dependence (sentimentality and sensitivity to others, and persistence) [7]. A functional polymorphism in a regulatory sequence for the serotonin transporter gene is associated with the emotional triad of neuroticism, depression and anxiety [8]. There are many more studies and observations which suggest considerable influence of genetic factors on normal and pathological personality traits and behaviour [3], [6], [7], [9].
Dani Rowland-Klein and Rosemary Dunlop [1], as well as other authors [10], [11], report that children of Holocaust survivors have some specific personality features. Some of these traits may be in part biologically inherited (i.e. inscribed in genes). It is possible that these features might help their parents to survive the horror of the Holocaust. These personality features may be pathological and maladaptive during the peacetime in the modern, rich, Western society, but the same behavioural traits might have been useful and helpful during the Second World War.
Contemporary research findings challenge most theories that consider child-rearing practices and environmental events the primary sources of variance in human personality [12]. It has been suggested that the term ‘nature versus nurture’ should be replaced by the term ‘nurture via nature’. Future research may clarify the role of genetic and environmental factors in the mechanisms of human behaviour.