Children react to environmental influences, such as parenting style, differently. Recent genetic studies have found that some children are affected more than others by environmental factors right from the start. They are born more susceptible to both positive and negative environment. This phenomenon is summarized in the Differential Susceptibility Hypothesis.
What is Differential Susceptibility
Differential susceptibility to environmental influence summarizes the observations that some individuals are disproportionately more susceptible to both negative and positive environmental conditions. It explains why people react differently to apparently same environment1.
Children vary in whether or not, or the degree to which, they are affected by the environment. That is, children vary in their susceptibility to rearing influence2.
Individuals with heightened susceptibility are more plastic or malleable. They are more sensitive to both beneficial and adverse rearing environments in early childhood3. This enhanced sensitivity to environmental influences can result in enduring developmental changes4.
Susceptibility to environmental influences is rooted in the biology of the nervous system. But besides neurobiology, experiences during the early years and early child care also play a role in determining individual differences in susceptibility5.
Diathesis Stress Model vs Differential Susceptibility Hypothesis
The Differential Susceptibility Hypothesis differs from the Diathesis Stress Model in how susceptible individuals are not just more vulnerable to negative conditions but they are more plastic to both positive and negative environment.
Decades of research demonstrates that exposure to environmental adversity, such as child maltreatment, unsupportive parenting, or negative life events, places children at elevated risk for developing antisocial behavior and psychopathology6. However, not all children would develop psychological or physical disorders under those conditions.
For over 30 years, the causes of this phenomenon are dominated by the Diathesis Stress Model (also known as the Dual Risk Model), which states that children with ‘difficult’ temperaments, or who carry certain risk allele, e.g. the s allele, are more likely to result in maladaptive outcomes when facing different stressors. Some individuals are predisposed or more vulnerable to certain health problems or psychological disorders than others.
The model, first proposed in the 1970s, serves to explain why some people are vulnerable to the negative effects of adversity while others remain unaffected and are more resilient7.
But psychologists have found that this model is largely incomplete. It doesn’t lend itself to a convincing explanation to why this is a desirable human trait.
Differential Susceptibility model addresses exactly this shortcoming.
In the differential susceptibility model, some individuals are more susceptible to both positive and negative conditions, in a for-better-and-for-worse manner. Hence, the susceptible characteristics are not liabilities, but plasticity traits8. Given supportive rearing and social environment, these people can reap the most benefit.
The Origin of Developmental Theories
From an evolutionary perspective, both supportive and adverse childhood environment have been part of human experience throughout our history. Differential susceptibility allow the human species to adapt to both kinds of contexts9.
Two different hypotheses, DST and BSCT, have emerged to interpret the existence of individual susceptibility to the environment.
While DST addresses the role of nature in natural selection, BSCT addresses the role of nurture. Although these two theories are unique, they do not exclude each other. In fact, they converge on the fact that susceptibility to rearing influence is an desirable evolutionary neurodevelopmental phenomenon in human development.
Differential-Susceptibility Theory (DST)
DST, proposed by Jay Belsky at the University of California, Davis, suggests that developmental plasticity is based on evolutionary biology and natural selection.
Evolutionarily, it is advantageous that children, especially within a family, vary in their susceptibility to both adverse and beneficial effects of rearing influence, because parents could not know for certain what rearing environment would maximize children’s survival. Differential susceptibility is proposed as a bet-hedging strategy in human evolution.
If an effect of the environment is proven counterproductive, the less susceptible children will be less affected. On the other hand, if a parenting style is proven beneficial, the more malleable offspring will benefit more.
This genetic variation allows the genes proven adaptable to the environment to pass on. As a result, humans, unlike other animals, can adapt to drastically different climates all across the world10,11.
Biological Sensitivity to Context Thesis (BSCT)
BSCT, proposed by Boyce from the University of California, Berkeley and Ellis from the University of Arizona, suggests that natural selection allows a child’s stress reactivity to develop adaptive outcomes according to their rearing environment12,13.
In stressful environments, children’s chances of survival and eventual reproduction is increased if they develop heightened sensitivity and vigilance to threat. The adaptation to childhood adversity “makes the best of a bad situation”14.
On the other hand, in supportive and enriched environments, increased reactivity allows children to adapt reproductively relevant processes and behaviors optimally such as growth, status, fertility, and offspring quality.
Under the BSCT regime, differential susceptibility is the result of the human stress-response system adapting to individual’s respective environment in early life.
Susceptibility factor is therefore more of a developmentally regulating strategy than a vulnerability or risk factor, even if those strategies may be harmful in terms of the long-term welfare of the individual or society as a whole in normal conditions.
Differential Susceptibility Markers
Differential susceptibility hypothesis has shed immense light on why children react differently to the same environment or parenting style.
Researchers have identified several potential differential susceptibility factors, called plasticity markers. These markers predict the differential susceptibility nature when interacting with the environment15.
There are three types of plasticity markers or factors:
- phenotypic (genetically related factor you can “see”)
- endophenotypic (genetically related factor “inside”)
- gene environment interaction
Here are some examples of these markers and the effects of their Parenting x Environment interaction.
Difficult temperament is defined as low inhibitory control, high dispositional frustration, high activity level and/or low soothability. It is a phenotypic factor (factor you can “see”) that demonstrates the differential nature of the child behavior.
In one study, researchers tracked the levels of externalizing behavior problems in a group of 16 to 19-month-old boys with difficult temperament. After 6 months, the boys who had mothers with high maternal sensitivity and infrequent use of negative control had the least increase in problem behavior. Those with highly insensitive mothers who relied heavily on negative control had the largest increase in behavioral issues. This effect was only found in the boys with difficult temperament16.
Every parent dreams of having a baby with easy temperament. These babies sleep better, eat better, tantrum less, and listen more. While having a difficult temperament predicts worse outcomes if the child is exposed to bad parenting17, it also predicts more positive outcomes if the child is raised with good parenting practice18.
Respiratory Sinus Arrhythmia & Cortisol Level
Respiratory Sinus Arrhythmia (RSA) & Cortisol reactivity are both endophenotypic factors (factor “inside”) of differential susceptibility.
RSA is related to an individual’s capacity to regulate stress while cortisol is linked to impulsivity, poor self control, peer rejection and aggression. These two markers are a gauge of stress reactivity, which in turn measures biological sensitivity to the environment.
In a study of 338 children of the age 5 to 6, researchers have found that children with high biological sensitivity, as measured by RSA and cortisol levels, showed the highest levels of conduct problems in negative family environment, but the highest levels of competence in positive family environment19.
5-HTTLPR is a genotype factor in the gene environment interaction effects (denoted as GxE). It is a polymorphism in the serotonin transporter gene area.
Neuroscientists have found that positive emotion was protective against psychiatric disorder. Children who have high levels of positive emotion are more resilient and have better self regulation. Those who have low levels are linked to depression and other psychological disorders.
Neurodevelopment study has shown that young people who carry two functional copies of the S’S’ 5-HTTLPR allele are more genetically susceptible to the quality of parenting. They have significantly more positive emotion when reared in supportive parenting environments and significantly lower levels of positive emotions in unsupportive environments.
On the other hand, those with at least one copy of the L 5-HTTLPR allele showed relatively consistent levels of positive emotion across both the supportive and unsupportive parenting environments. These findings are consistent with the differential susceptibility hypothesis20.
Differential Susceptibility and Parenting
Whether, how, and to what extent parenting affects a child’s development has been a longstanding interest to developmental psychologists, child psychology researchers, parents and educators.
Although there is an enormous amount of studies consistently proving parenting’s effects on child development, these correlational research is open to question regarding cause and effect. The question of why a shared environment in the form of parenting often cannot explain the variance in developmental outcomes among siblings remains.
In addition, researchers consistently find that parenting of identical twins is more similar than parenting of fraternal twins and that two biological siblings typically experience more similar parenting than do two adopted children.
The discovery of neurobiologically susceptibility has provided a much needed additional perspective on this “does parenting matter” question.
A shared childhood environment can provide similar experiences, but it can affect different children in different ways, including some not at all. When this happens, the shared-environment component in behavior-genetic research becomes a non-shared environment component.
Due to genetic sensitivity, the influence of life stress on a child’s development are “neither as unambiguous as earlier researchers suggested nor as insubstantial as behavior-genetics researchers claim.”21
As parents, while we cannot change our biological makeup, we can make the rearing environments safe and supportive for even the most sensitive children to thrive.
- 1.Ellis BJ, Boyce WT, Belsky J, Bakermans-Kranenburg MJ, van Ijzendoorn MH. Differential susceptibility to the environment: An evolutionary–neurodevelopmental theory. Dev Psychopathol. Published online January 24, 2011:7-28. doi:10.1017/s0954579410000611
- 2.Belsky J. Differential Susceptibility to Rearing Influence: An Evolutionary Hypothesis and Some Evidence. In: Origins of the Social Mind: Evolutionary Psychology and Child Development. Guilford Press; 2005:139–163.
- 3.Bakermans-Kranenburg MJ, van IJzendoorn MH. Research Review: Genetic vulnerability or differential susceptibility in child development: the case of attachment. Journal of Child Psychology and Psychiatry. Published online December 2007:1160-1173. doi:10.1111/j.1469-7610.2007.01801.x
- 4.Boyce WT. Differential Susceptibility of the Developing Brain to Contextual Adversity and Stress. Neuropsychopharmacol. Published online September 22, 2015:142-162. doi:10.1038/npp.2015.294
- 5.Lutha S, Cicchetti D. The construct of resilience: implications for interventions and social policies. Dev Psychopathol. 2000;12(4):857-885. doi:10.1017/s0954579400004156
- 6.Shonkoff JP, Boyce WT, McEwen BS. Neuroscience, Molecular Biology, and the Childhood Roots of Health Disparities. JAMA. Published online June 3, 2009:2252. doi:10.1001/jama.2009.754
- 7.Walker EF, Diforio D. Schizophrenia: A neural diathesis-stress model. Psychological Review. Published online 1997:667-685. doi:10.1037/0033-295x.104.4.667
- 8.Belsky J, Pluess M. Beyond diathesis stress: Differential susceptibility to environmental influences. Psychological Bulletin. Published online 2009:885-908. doi:10.1037/a0017376
- 9.Belsky J. Variation in Susceptibility to Environmental Influence: An Evolutionary Argument. Psychological Inquiry. Published online July 1997:182-186. doi:10.1207/s15327965pli0803_3
- 10.Belsky J. Theory Testing, Effect-Size Evaluation, and Differential Susceptibility to Rearing Influence: The Case of Mothering and Attachment. Child Development. Published online August 1997:598. doi:10.2307/1132110
- 11.Belsky J, Bakermans-Kranenburg MJ, van IJzendoorn MH. For Better and For Worse. Curr Dir Psychol Sci. Published online December 2007:300-304. doi:10.1111/j.1467-8721.2007.00525.x
- 12.BOYCE WT, ELLIS BJ. Biological sensitivity to context: I. An evolutionary–developmental theory of the origins and functions of stress reactivity. Develop Psychopathol. Published online May 12, 2005. doi:10.1017/s0954579405050145
- 13.Ellis BJ, Boyce WT. Differential susceptibility to the environment: Toward an understanding of sensitivity to developmental experiences and context. Dev Psychopathol. Published online 2011:1-5. doi:10.1017/s095457941000060x
- 14.Hinde RA, Stevenson-Hinde J. Attachment: Biological, Cultural and Individual Desiderata. Human Development. Published online 1990:62-72. doi:10.1159/000276503
- 15.Belsky J, Jonassaint C, Pluess M, Stanton M, Brummett B, Williams R. Vulnerability genes or plasticity genes? Mol Psychiatry. Published online May 19, 2009:746-754. doi:10.1038/mp.2009.44
- 16.van Aken C, Junger M, Verhoeven M, van Aken MAG, Deković M. The interactive effects of temperament and maternal parenting on toddlers’ externalizing behaviours. Inf Child Develop. Published online 2007:553-572. doi:10.1002/icd.529
- 17.Morris AS, Silk JS, Steinberg L, Sessa FM, Avenevoli S, Essex MJ. Temperamental Vulnerability and Negative Parenting as Interacting Predictors of Child Adjustment. J Marriage and Family. Published online May 2002:461-471. doi:10.1111/j.1741-3737.2002.00461.x
- 18.Kochanska G, Aksan N, Joy ME. Children’s fearfulness as a moderator of parenting in early socialization: Two longitudinal studies. Developmental Psychology. Published online 2007:222-237. doi:10.1037/0012-1622.214.171.124
- 19.Obradović J, Bush NR, Stamperdahl J, Adler NE, Boyce WT. Biological Sensitivity to Context: The Interactive Effects of Stress Reactivity and Family Adversity on Socioemotional Behavior and School Readiness. Child Development. Published online January 2010:270-289. doi:10.1111/j.1467-8624.2009.01394.x
- 20.Hankin BL, Nederhof E, Oppenheimer CW, et al. Differential susceptibility in youth: evidence that 5-HTTLPR x positive parenting is associated with positive affect ‘for better and worse.’ Transl Psychiatry. Published online October 2011:e44-e44. doi:10.1038/tp.2011.44
- 21.Collins WA, Maccoby EE, Steinberg L, Hetherington EM, Bornstein MH. Contemporary research on parenting: The case for nature and nurture. American Psychologist. Published online 2000:218-232. doi:10.1037/0003-066x.55.2.218