Michael Pluess

Vulnerability genes or plasticity genes

The classic diathesis–stress framework, which views some individuals as particularly vulnerable to adversity, informs virtually all psychiatric research on behavior–gene–environment (G × E) interaction. An alternative framework of ‘differential susceptibility’ is proposed, one which regards those most susceptible to adversity because of their genetic make up as simultaneously most likely to benefit from supportive or enriching experiences—or even just the absence of adversity. Recent G × E findings consistent with this perspective and involving monoamine oxidase-A, 5-HTTLPR (5-hydroxytryptamine-linked polymorphic region polymorphism) and dopamine receptor D4 (DRD4) are reviewed for illustrative purposes. Results considered suggest that putative ‘vulnerability genes’ or ‘risk alleles’ might, at times, be more appropriately conceptualized as ‘plasticity genes’, because they seem to make individuals more susceptible to environmental influences—for better and for worse.

Vantage Sensitivity: Individual Differences in Response to Positive Experiences

The notion that some people are more vulnerable to adversity as a function of inherent risk characteristics is widely embraced in most fields of psychology. This is reflected in the popularity of the diathesis-stress framework, which has received a vast amount of empirical support over the years. Much less effort has been directed toward the investigation of endogenous factors associated with variability in response to positive influences. One reason for the failure to investigate individual differences in response to positive experiences as a function of endogenous factors may be the absence of adequate theoretical frameworks. According to the differential-susceptibility hypothesis, individuals generally vary in their developmental plasticity regardless of whether they are exposed to negative or positive influences--a notion derived from evolutionary reasoning. On the basis of this now well-supported proposition, we advance herein the new concept of vantage sensitivity, reflecting variation in response to exclusively positive experiences as a function of individual endogenous characteristics. After distinguishing vantage sensitivity from theoretically related concepts of differential-susceptibility and resilience, we review some recent empirical evidence for vantage sensitivity featuring behavioral, physiological, and genetic factors as moderators of a wide range of positive experiences ranging from family environment and psychotherapy to educational intervention. Thereafter, we discuss genetic and environmental factors contributing to individual differences in vantage sensitivity, potential mechanisms underlying vantage sensitivity, and practical implications.

The Nature (and Nurture?) of Plasticity in Early Human Development.

The effect of early experience is a long-standing concern in developmental psychology. Gaining further insight into the nature of human plasticity is central to efforts to prevent problems in development from arising and promote positive functioning. Evolutionary reasoning suggests that children should vary in their susceptibility to environmental influences, including parenting. Evidence indicates that rather than some children, such as those with negatively emotional temperaments or certain genotypes, being simply more vulnerable to the adverse effects of negative experiences, as commonly assumed, they may actually be more susceptible to both positive and negative experiences. In addition to raising questions about the nature of plasticity in human development, this article highlights unknowns regarding the role of nature and nurture in shaping individual differences in plasticity, including whether recent research linking maternal stress during pregnancy with child behavior problems illuminates a process whereby fetal programming shapes the childs susceptibility to postnatal environmental influences. Throughout this article, we raise concern about the potentially distorting influence that psychologys disproportionate focus on the adverse effect of negative experiences on developmental problems has on our understanding of human plasticity, and we propose that researchers should pay more attention to the positive side of the plasticity equation.

Differential Susceptibility to Rearing Experience: The Case of Childcare.

BACKGROUND Inconsistencies regarding developmental effects of non-maternal childcare may be caused by neglecting the possibility that children are differentially susceptible towards such experiences. METHOD Interactions between difficult/negative child temperament and childcare type, quantity, and quality on teacher-rated behavior problems and social competence at 54 months and in kindergarten were investigated via multiple regression using data from the NICHD Study of Early Child Care. RESULTS Childcare quality interacted with infant negativity in predicting behavior problems and social competence, whereas effects of quantity and type were independent of child temperament. Consistent with Belskys (1997) differential susceptibility hypothesis, children with difficult temperaments as infants exhibited both more behavior problems when faced with low quality care and fewer when experiencing high quality care than children with easy temperaments. CONCLUSIONS Negatively-emotional infants appear to be more affected by the quality of care they experience - both negatively and positively - than other young children.

Differential Susceptibility to Parenting and Quality Child Care

Research on differential susceptibility to rearing suggests that infants with difficult temperaments are disproportionately affected by parenting and child care quality, but a major U.S. child care study raises questions as to whether quality of care influences social adjustment. One thousand three hundred sixty-four American children from reasonably diverse backgrounds were followed from 1 month to 11 years with repeated observational assessments of parenting and child care quality, as well as teacher report and standardized assessments of childrens cognitive-academic and social functioning, to determine whether those with histories of difficult temperament proved more susceptible to early rearing effects at ages 10 and 11. Evidence for such differential susceptibility emerges in the case of both parenting and child care quality and with respect to both cognitive-academic and social functioning. Differential susceptibility to parenting and child care quality extends to late middle childhood. J. Belsky, D. L. Vandell, et al.s (2007) failure to consider such temperament-moderated rearing effects in their evaluation of long-term child care effects misestimates effects of child care quality on social adjustment.

Beyond risk, resilience, and dysregulation: Phenotypic plasticity and human development

We provide a theoretical and empirical basis for the claim that individual differences exist in developmental plasticity and that phenotypic plasticity should be a subject of study in its own right. To advance this argument, we begin by highlighting challenges that evolutionary thinking poses for a science of development and psychopathology, including for the diathesis-stress framework that has (fruitfully) guided so much empirical inquiry on developmental risk, resilience, and dysregulation. With this foundation laid, we raise a series of issues that the differential-susceptibility hypothesis calls attention to, while highlighting findings that have emerged over just the past several years and are pertinent to some of the questions posed. Even though it is clear that this new perspective on Person × Environment interaction is stimulating research and influencing how hypotheses are framed and data interpreted, a great many topics remain that need empirical attention. Our intention is to encourage students of development and psychopathology to treat phenotypic plasticity as an individual-difference construct while exploring unknowns in the differential-susceptibility equation.

Serotonin transporter polymorphism moderates effects of prenatal maternal anxiety on infant negative emotionality.

BACKGROUND Consistent with the fetal programming hypothesis, effects of maternal prenatal anxiety have been found to predict various measures of infant temperament in the early postnatal period. In recent years, a polymorphism in the serotonin transporter gene (5-HTTLPR) emerged as a moderator of diverse environmental influences on different outcomes, with individuals carrying the short allele being generally more vulnerable to adversity. METHODS We tested whether the association between self-reported maternal anxiety at 20 weeks gestation (Brief Symptom Inventory) and mother-rated infant negative emotionality at 6 months after birth (Infant Behavior Questionnaire-Revised) would be moderated by the 5-HTTLPR in a large Dutch cohort sample (n = 1513). We hypothesized that infants carrying the 5-HTTLPR short allele would be more susceptible and therefore more affected by both low and high prenatal maternal anxiety vis-à-vis negative emotionality than other genotypes. RESULTS Findings of a significant gene × environment interaction (B = .65, p = .01) were supportive of a vulnerability model, with infants carrying the short allele being more negatively emotional when mothers reported anxiety during pregnancy, whereas there was no difference between genotypes on negative emotionality when maternal anxiety was low. CONCLUSIONS The association between maternal anxiety during pregnancy and negative emotionality in early infancy was significant in infants carrying one or more copies of the short allele but not in those homozygous for the long allele. The 5-HTTLPR short allele might increase vulnerability to adverse environmental influences as early as the fetal period.

Distinguishing ordinal and disordinal interactions.

Re-parameterized regression models may enable tests of crucial theoretical predictions involving interactive effects of predictors that cannot be tested directly using standard approaches. First, we present a re-parameterized regression model for the Linear × Linear interaction of 2 quantitative predictors that yields point and interval estimates of 1 key parameter-the crossover point of predicted values-and leaves certain other parameters unchanged. We explain how resulting parameter estimates provide direct evidence for distinguishing ordinal from disordinal interactions. We generalize the re-parameterized model to Linear × Qualitative interactions, where the qualitative variable may have 2 or 3 categories, and then describe how to modify the re-parameterized model to test moderating effects. To illustrate our new approach, we fit alternate models to social skills data on 438 participants in the National Institute of Child Health and Human Development Study of Early Child Care. The re-parameterized regression model had point and interval estimates of the crossover point that fell near the mean on the continuous environment measure. The disordinal form of the interaction supported 1 theoretical model-differential-susceptibility-over a competing model that predicted an ordinal interaction.

5-HTTLPR moderates effects of current life events on neuroticism: differential susceptibility to environmental influences.

Research chronicling links between a polymorphism in the serotonin-transporter gene (5-HTTLPR) and neuroticism has yielded inconsistent results. One possible explanation for this inconsistency is that any gene-phenotype association is obscured by a gene-X-environment (GXE) interaction. We studied a healthy non-clinical sample (N=118) to determine whether the 5-HTTLPR interacts with current life events in predicting neuroticism. The differential-susceptibility hypothesis led to the prediction of such an interaction, reflecting the fact that individuals with short alleles would be affected more by both negative and positive life events than those homozygous for long alleles. Participants completed questionnaires concerning recent life events and neuroticism. The 5-HTTLPR was genotyped using a standard protocol with DNA extracted from oral fluid. For those homozygous for the short allele, more negative life events proved related to greater neuroticism, whereas more positive life events proved related to less neuroticism. No such association emerged in the case of those homozygous for the long allele. Whereas neuroticism is likely to be an especially stable trait in individuals homozygous for the long allele, this may be less so the case for those carrying short alleles.

Maternal trait anxiety, emotional distress, and salivary cortisol in pregnancy

Animal models suggest that stress-induced hormonal changes in the mother during pregnancy lead to enduring changes in the fetus and empirical links between prenatal maternal stress and negative child development have been discerned repeatedly in human studies. But the role of heritable personality traits has received little attention in the latter work. The goal of the current study was to investigate the relationship between maternal personality, psychological measures of maternal distress and maternal salivary cortisol during pregnancy. Maternal reports of personality (16 PF) and stress-related psychological measures (depression, pregnancy-related anxiety, perceived stress, negative life events) as well as salivary cortisol samples of 66 healthy pregnant women were collected in early and late pregnancy. Maternal trait anxiety proved related to all stress-related psychological measures and high anxiety predicted low baseline cortisol awakening levels in early pregnancy. Maternal trait anxiety is related to both psychological and biological stress measures during pregnancy.