Differential susceptibility

The differential susceptibility theory proposed by Jay Belsky[1] is another interpretation of psychological findings that are usually discussed according to the diathesis-stress model.

[5] These theories suggested that some "vulnerable" individuals, due to their biological, temperamental and/or physiological characteristics (i.e., "diathesis" or "risk 1"), are more vulnerable to the adverse effects of negative experiences (i.e., "stress" or "risk 2"), while other "resilient" individuals are not affected by these negative experiences (see Figure 1).

As a result, and as a fitness optimizing strategy involving bet hedging,[10] natural selection might have shaped parents to bear children varying in plasticity.

Importantly, natural selection might favour genetic lines with both plastic and fixed developmental and affective patterns.

This line of evolutionary argument leads to the prediction that children should vary in their susceptibility to parental rearing and perhaps to environmental influences more generally.

As it turns out, a long line of developmental inquiry, informed by a "transactional" perspective,[12] has more or less been based on this unstated assumption.

Belsky, Bakermans-Kranenburg, & Van IJzendoorn, (2007) delineated a series of empirical requirements—or steps—for evidencing the differential susceptibility hypothesis.

Bakermans-Kranenburg and Van IJzendoorn (2006) were the first to test the differential susceptibility hypothesis as a function of Genetic Factors regarding the moderating effect of the dopamine receptor D4 7-repeat polymorphism (DRD4-7R) on the association between maternal sensitivity and externalizing behavior problems in 47 families.

Table 1. List of Proposed Susceptibility Factors that emerge across studies, according to Belsky and colleagues.