Frequency of Infant Stroking Reported by Mothers Moderates the Effect of Prenatal Depression on Infant Behavioural and Physiological Outcomes

Abstract

Animal studies find that prenatal stress is associated with increased physiological and emotional reactivity later in life, mediated via fetal programming of the HPA axis through decreased glucocorticoid receptor (GR) gene expression. Post-natal behaviours, notably licking and grooming in rats, cause decreased behavioural indices of fear and reduced HPA axis reactivity mediated via increased GR gene expression. Post-natal maternal behaviours may therefore be expected to modify prenatal effects, but this has not previously been examined in humans. We examined whether, according to self-report, maternal stroking over the first weeks of life modified associations between prenatal depression and physiological and behavioral outcomes in infancy, hence mimicking effects of rodent licking and grooming. From a general population sample of 1233 first time mothers recruited at 20 weeks gestation we drew a stratified random sample of 316 for assessment at 32 weeks based on reported inter-partner psychological abuse, a risk to child development. Of these 271 provided data at 5, 9 and 29 weeks post delivery. Mothers reported how often they stroked their babies at 5 and 9 weeks. At 29 weeks vagal withdrawal to a stressor, a measure of physiological adaptability, and maternal reported negative emotionality were assessed. There was a significant interaction between prenatal depression and maternal stroking in the prediction of vagal reactivity to a stressor (p = .01), and maternal reports of infant anger proneness (p = .007) and fear (p = .043). Increasing maternal depression was associated with decreasing physiological adaptability, and with increasing negative emotionality, only in the presence of low maternal stroking. These initial findings in humans indicate that maternal stroking in infancy, as reported by mothers, has effects strongly resembling the effects of observed maternal behaviours in animals, pointing to future studies of the epigenetic, physiological and behavioral effects of maternal stroking.

Sex differences in the associations between vagal reactivity and oppositional defiant disorder symptoms

“…The study design has been previously described (Sharp, Hill, Hellier, & Pickles, 2015; Sharp et al., 2012; Tibu et al., 2014). Recruited from consecutive attendees at the 20‐week prenatal check, the full cohort of 1,233 primiparous mothers with a mean age of 26.8 years ( SD  = 5.8, range 18–51) were all women who gave birth to a live, singleton baby eligible for longitudinal follow‐up.…”

“…The patterns of RSA across the five procedures were very similar in males and females, and there were no significant sex differences in any procedure (Tibu et al., 2014). A principal components analysis yielded a single factor with an eigenvalue of 3.54 that explained 70.73% of the total variance (Sharp et al., 2012). All five RSA values loaded highly on to the factor (factor loadings .86, .84, .84, .84, .82) supporting the existence of a latent variable which could be construed as ‘resting’ or ‘baseline’.…”

Mapping early environment using communication deviance: A longitudinal study of maternal sensitivity towards 6-month-old children

“…This two stage stratified design enables intensive measurement in the subsample, including assessment of CD and maternal sensitivity, while collection of other measures across the extensive sample allows weighting back of the findings from the intensive subsample to give general population estimates. A detailed flowchart of the sampling and recruitment procedure can be found elsewhere (Sharp et al, 2012) …”

“…Described in detail in Sharp et al (2012) the full cohort of 1233 WCHADS mothers with live singleton births have participated in several waves of assessment but a stratified random sub-sample of 316 was drawn for additional more intensive assessment. FMSS at 32 weeks gestation were available for 287 women in the intensive sub-sample and 272 mother-infant dyads were later observed in interaction at 29 weeks.…”

Measurement of callous-unemotional traits in very young children: a psychometric and validity study from 2.5 to 5.0 years

“…All women gave written informed consent at the point of recruitment in the antenatal clinic. The study used a two stage stratified design in which a consecutive general population sample (the 'extensive' sample) is used to generate a smaller 'intensive' sample stratified by psychosocial risk with more detailed measurement over time and both are followed in tandem (Sharp et al, 2012). …”