More nature-nurture: Low-birth-weight children are particularly vulnerable to environmental influences

The interaction between nature (genes often) and nurture is a fascinating field of research. New research focuses on low-birth-weight children.

From the press release:

Psychologists put competing development models to the test

Low birth weight children are more vulnerable to environmental influences than infants born with normal weight. When brought up with a great deal of sensitivity, they will be able to catch up in school, but on average they will not become better students than normal birth weight children. This result, provided by an international psychologist team, has confirmed the so-called diathesis-stress model of development for low birth weight populations. The researchers report their findings in the Journal of Child Psychology and Psychiatry.

Theories on how environmental factors affect development

Psychological theories assume that some children are more susceptible to environmental influences than others – regardless if those influences are positive or negative. Unlike the diathesis-stress model, the new differential susceptibility model assumes that children who are particularly susceptible will outperform less susceptible children under optimal environmental conditions, even though their increased susceptibility may be due to a risk factor such as difficult temperament. Together with colleagues from the UK and the USA, Dr Julia Jäkel from the work unit Developmental Psychology at the Ruhr-Universität Bochum analysed which of these two models best represents low birth weight children’s development.

Data of 922 children analysed

In their analysis, the researchers studied 922 children with a birth weight between 600 and 5140 grams. The data were derived from the Bavarian Longitudinal Study. The study team had assessed maternal sensitivity via standardised behaviour observations of mother-child interactions at age six years. At age eight, all children underwent a series of standardised tests assessing their mathematic, reading and writing competencies. The researchers compared the academic performance of children with a very low birth weight, i.e. less than 1500 grams, resp. low birth weight (1500 to 2499 grams), with the performance of children with a normal birth weight of at least 2500 grams.

Makes evolutionary sense

The differential susceptibility model has an evolutionary background. “Even if all parents in one generation would raise their children in a completely wrong way, every individual child would develop differently, because some of them would not be affected by bad parenting,” says Dr Julia Jäkel. “This is what ensures the survival of our species.”

Abstract of the research:

Background
Differential Susceptibility Theory (DST) postulates that some children are more affected – for better and for worse – by developmental experiences, including parenting, than others. Low birth weight (LBW, 1,500–2,499 g) may not only be a predictor for neurodevelopmental impairment but also a marker for prenatally programmed susceptibility. The aim was to test if effects of sensitive parenting on LBW and very LBW (VLBW, <1,500 g) versus normal birth weight (NBW, ≥2,500 g) children’s academic achievement are best explained by a differential susceptibility versus diathesis-stress model of person-X-environment interaction.

Methods
Nine hundred and twenty-two children ranging from 600 g to 5,140 g birth weight were studied as part of a prospective, geographically defined, longitudinal investigation of neonatal at-risk children in South Germany (Bavarian Longitudinal Study). Sensitive parenting during a structured mother–child interaction task was observed and rated at age 6 years. Academic achievement was assessed with standardized mathematic, reading, and spelling/writing tests at age 8 years.

Results
Maternal sensitivity positively predicted the academic achievement of both LBW (n = 283) and VLBW (n = 202) children. Confirmatory-comparative and model-fitting analysis (testing LBW vs. NBW and VLBW vs. NBW) indicated that LBW and VLBW children were more susceptible than NBW to the adverse effects of low-sensitive, but not beneficial effects of high-sensitive parenting.

Conclusions
Findings proved more consistent with the diathesis stress than differential-susceptibility model of person-X-environment interaction: LBW and VLBW children’s exposure to positive parenting predicted catch-up to their NBW peers, whereas exposure to negative parenting predicted much poorer functioning.

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