Associations between Maternal Postnatal Depression and Infants’ Social Learning Abilities Oliver Perra, Rebecca Phillips, Rhiannon Fyfield, Cerith Waters, Dale F. Hay, & the Cardiff Child Development Study Team Method Families (N=332) enrolled on the Cardiff Child Development Study (CCDS), a nationally representative prospective longitudinal study of first born children in Wales, UK. Acknowledgements The research was supported by MRC Programme Grant GO to Dale F. Hay at Cardiff University. We thank other members of the CCDS team and all the families from the CCDS who gave so generously of their time. Introduction Previous research has provided evidence of links between maternal postnatal depression (PND) and cognitive development of the child. However, relatively few studies have investigated the potential mechanisms that might explain these associations. Some studies suggest that maternal PND may act by disrupting infants’ learning abilities. Aims of this study To test whether exposure to maternal PND disrupts infants learning experiences, we investigated if infants of mothers who experienced PND were less successful in social learning tasks. These tasks tested 12-month-olds’ imitation of instrumental and arbitrary actions displayed by an adult model. Furthermore, in order to investigate the characteristics of mother-infant interaction that may explain the effect of maternal PND, we also tested if PND mothers were less likely to express positive affect and use infant-focused speech, and, if so, whether these dimensions of mother-infant interaction influenced infants’ subsequent social learning abilities. Pregnancy home visit Interviews with mothers and fathers Early infancy home visit (mean age 6.6) Parental interview; Infant- caregiver observations (88% mothers) in 3 tasks: free play; activity board interaction; feeding task. 3 rd Trimester Pregnancy (N=332) Birth 6 months (N=301) 12 months (N=275) Late infancy laboratory visit (mean age 12.8) Tests of infants’ abilities and observation of peer interaction Measures Mother’s psychopathology before and after childbirth. Assessed using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN: Wing et al., 1990). Coded according to DSM-IV diagnostic criteria for Depressive Disorder prior to conception, during the pregnancy or in the first six-months postpartum. Inter-rate agreement was acceptable (Cohen’s kappa ranging from.79 to.81). Socio-demographic adversity during pregnancy index. Created using Principal Component Analysis. Indicators: (a) failure to achieve basic educational attainments; (b) mother in her teens; (c) mother not legally married; (d) mother not in a stable relationship; (e) mother classified as working class. All items contributed to a single component explaining 77% of shared variance. Parents’ positive affect (positive and laughing) in the early infancy home visit. Coded using 10-sec interval time sampling across the parent-infant interaction tasks. A measurement model was used to generate a single factor score. Independent observers recorded 34% of the videos with good agreement (median ICC=.96). Maternal speech during the Activity Board Task (early infancy home visit). Speech transcribed and separated into temporal units of 5 sec (24 units per participant). Each 5-sec interval in which mother spoke was subsequently coded in terms of references to the infants’ thoughts and feelings. Two independent raters coded 10% of participants with median agreement κ =.90. Results Incidence of Postnatal Depression: 34 women (11% of those interviewed, which is in line with prevalence rates) met DSM-IV criteria for depression in the first 6 months postpartum. Half of them had been depressed in pregnancy. Women with PND had experienced a higher level of socio-economic adversity compared to non-depressed women. Infants’ imitation: 253 completed the task. 174 (69%) imitated a modelled action at least once across the two tasks. The instrumental action was imitated by 63% of the sample, while the arbitrary action was imitated by 22%. PND and infants’ imitation: Differences in imitation were particularly evident in the arbitrary imitation task (Fisher’s exact test p=.040, 1-sided), compared to the instrumental imitation task (Fisher’s exact test p>.05). Only 1 infant (5%) whose mother met criteria for PND imitated in the arbitrary imitation task, compared to 53 (24%) of the other infants. Overall, infants of women who had experienced PND imitated significantly less across the two tasks compared to infants not exposed to maternal PND, χ 2 (1)= 4.52, p =. 03, see Figure 3. A logistic regression confirmed exposure to PND was associated with reduced odds of imitation (OR=.28; 95% CI.10 to.76). This association was not explained by socio- demographic adversity. Figure 1. Study design and procedure PND, Infant-Focused Speech and Imitation Ability: Maternal expression of positive affect was not associated with imitation, while infants who imitated at 12 months had been more likely to hear mothers using speech about the infant’s feelings and thoughts at 6 months, t(217)= -2.29, p =.02. A logistic regression indicated that significant associations between imitation at 12 months and PND were observed even when controlling for the association between imitation and maternal speech about the infant’s thoughts and feelings. PND was associated with a significant reduction in the odds of displaying imitation at 12 months, see Table 1. Figure 3. Imitation in at least one task by PND Instrumental and Arbitrary Imitation tasks. Adapted from Carpenter, Nagell & Tomasello (1998). A specially designed box was embedded with three objects (Figure 2). A 1-min baseline period where the infant played with the box, followed by the two tasks. In each task, the experimenter demonstrated an action 3 times and then asked the infant to do the same (1 min). Order of tasks was counterbalanced. Instrumental action task: the model manipulated a structural feature of the box, e.g., a lever, leading to a contingent outcome. Arbitrary action task: the experimenter made an arbitrary hand movement (e.g., tapping on the surface of the box), which led to a different contingent outcome. Inter-agreement based on 25% of cases: κ =.83. Discussion The study provides support for a link between exposure to PND and cognitive outcomes (e.g. Murray, 1992). Maternal PND may exert specific effects on learning abilities (Hay, 1997). Infants displayed difficulties particularly in imitation of arbitrary actions: this type of imitation is less likely to rely on the affordances provided by the object and is considered a more robust test of true imitation (Carpenter, Nagell, & Tomasello, 1998). Mothers’ speech about the infant’s thoughts and feeling fostered imitation. Infant-focused maternal speech is also associated with infants’ joint attention (Roberts et al., 2013). This dimension of parent-infant early interactions may play an important role in fostering socio-cognitive development. Overall, the results suggest that depression after childbirth may impact negatively on infants’ early learning environments. More theoretically- guided studies on early cognitive and socio-cognitive development are needed to understand the mechanisms underlying the effect of PND. Figure 2. The imitation box