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|کد مقاله||سال انتشار||تعداد صفحات مقاله انگلیسی||ترجمه فارسی|
|38118||2012||12 صفحه PDF||سفارش دهید|
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Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : Infant Behavior and Development, Volume 35, Issue 4, December 2012, Pages 803–814
Abstract The effect of maternal depression on the trajectories of cognitive development was studied in 26 infants with depressed mothers as compared to a group of 24 infants with non-depressed mothers. The infants were tested on Mullen Scales of Early Learning when they were 6, 12 and 18 months old. Mothers reported their depressive symptoms over the follow ups. The study also investigated if there were sex differences in the cognitive trajectories. Multilevel modeling analyses revealed that infants of depressed mothers had a stable lower cognitive score over the period 6–18 months of age as compared to the infants of non-depressed mothers, and that the girls tended to increase their cognitive scores as compared to the boys over the same time period. The results are discussed in light of the stability of depression symptoms over the follow up and sex differences in cognitive development.
. Introduction The effects of maternal postnatal depression on child cognitive functioning are inconsistent. Some research shows a relation between maternal depression and reduced cognitive performance (Hay et al., 2001 and Murray, 1992). Others find a relation under specific conditions such as chronic depression, or for specific groups such as male infants or low educated parents (Hay and Kumar, 1995 and Murray et al., 1993). In an attempt to explain the inconsistency in results, researchers have looked to the timing and duration of depression and gender interactions. Different types of studies have demonstrated that maternal depression of longer duration in infancy is contributing to poorer cognitive development in infants and older children (Cicchetti et al., 2000, NICHD, 1999a, NICHD, 1999b, Petterson and Alison Burke, 2001 and Sutter-Dallay et al., 2011). The impact of brief and less chronic depression on child cognitive development is less clear, but there are some studies indicating that even brief postnatal depression may have long lasting effect on cognitive development (Hay et al., 2001). Still, it is unclear how maternal postnatal depression is related to individual change in cognitive abilities since few have done longitudinal studies with repeated measures of cognitive capacity. One exception is a stud by Feldman and Eidelman (2009) who investigated if vagal tone and maternal postpartum depressive symptoms influenced premature infants’ trajectory of cognitive development assessed at infant corrected ages 6, 12 and 24 months and again at 5 years. Their results showed different timing of the two factors: higher vagal tone increased the rate of cognitive development across the first years of life, whereas maternal postpartum depressive symptoms interfered with development in the preschool years. Unfortunately, they did not track depressive symptoms during the follow-up period, neither did they use clinical interview for depression, so it is uncertain which aspect of maternal depression, the early timing or the severity or chronicity that was influencing the change in cognitive development in the preschool years. The current study aimed to investigate if maternal clinical depression and gender are related to change in infant cognitive abilities through the first 18 months of life. 1.1. Maternal depression and change in infant cognitive development Murray, Hipwell, Hooper, Stein, and Cooper (1996) and Murray (1992) measured object permanence tasks in a group of 9 months old infants with postnatal depressed mothers, and tested their cognitive abilities at 18 months and again at 5 years of age. At 9 months infants with depressed mothers performed less well than infants in a control group with healthy mothers on the object permanence task. At 18 months of age there were no overall effects of maternal depression, although boys and infants in families with lower socioeconomic status were affected by maternal depression. At follow-up at 5 years of age there were no relations between concurrent maternal depressions and the severity or duration of postnatal depression, also the boys and disadvantaged groups exposed to maternal postnatal depression were accomplishing as well as the non-depression group. Even though the infants of depressed mothers were initially inferior on the object permanence tasks they were gradually performing as well as the comparison group on the cognitive tests. In another longitudinal study (Hay et al., 2001) it was shown that children exposed to maternal postnatal depression had lower cognitive abilities when assessed on WISC at 4 and 11 years of age as compared to children with non-depressed mothers. The difference persisted after control for both concurrent depression and maternal IQ. The differential results may partly be due to differential social contexts, such as the quality of education that might have influenced the children's cognitive performance (Bronfenbrenner, 1979 and Murray et al., 1996). Sutter-Dallay and colleagues (2010) assessed both maternal depressive symptoms and infant cognitive development repeatedly during the infants’ two first years of life. They found a significant relation between maternal depressive symptoms at infant age 6 weeks and infant cognitive development over the two first years of life. When taking into account the mothers’ subsequent depressive symptoms over the two first years of life, this relation was reduced to a statistically insignificant trend. They also found that depressive symptoms at infant age 6 weeks strongly predicted the symptoms levels in mothers at all follow up assessments. The results suggest that the effect of early maternal depression on infant cognitive development is partly mediated by subsequently elevated depressive symptoms. In summary, the results from the previous longitudinal studies suggest that there is a change in children's cognitive abilities over time that is related to maternal postnatal depression, but it is unclear how this change is taking place. It is also unclear how early it is possible to assess a relation between maternal depression and change in children's cognitive performance. The human brain is developing structurally and functionally over a much longer time span as compared to other primates (Johnson, 2005). This implies that the developing child will be affected differentially by the environment at different phases in development. The influence of maternal depressive symptoms on the young child's cognitive performance could vary as a function of timing in brain development and the duration of exposure to maternal depression. The very young infant's brain and perceptual system are tuned to detecting contingency between its own reactions and environmental events. Also, the young infants’ immobility demands that caregivers in some way bring the social and physical environment to them. Exposure to an insensitive and depressed mother from a very early age and for a longer period may turn the infant into a state of learned helplessness (Seligman, 1975). Kaplan and colleagues (2011) showed that 1-year old infants of currently depressed mothers with prenatal depression onset, to a lesser degree took advantage of infant-directed speech produced by a non-depressed mother as compared to infants with currently exposure to maternal depression with later onset. Their results suggested that the infants had generalized their response to infant-directed speech from the depressed mothers’ to the non-depressed mothers’ speech. A depressed mothers’ speech to her infant is less pitched (Kaplan, Bachorowski, Smoski, & Zincer, 2001) and refers less to the infants’ agency (Murray et al., 1993). Infants exposed to a self-occupied mother may gradually tune out from her because there are less reinforcing activities like imitation and expansion of the infants’ experience. Infants exposed to maternal depression for a longer time may generally come to expect less stimulating responses from women. On the other hand, exposure to maternal depression may also fail to support later developing functions, such as the child's autonomy (Kochanska & Leon, 1991), verbal IQ (Cicchetti et al., 2000) and executive functions in toddlerhood and childhood (Rohrer, Cicchetti, Rogosch, Toth, & Maughan, 2011). Feldman and Eidelman (2009) found that maternal depressive symptoms measured before discharge had its strongest impact on infants’ trajectories of cognitive development between 2 and 5 years of age. The researchers concluded that depressive mothers may have special difficulties in supporting functions emerging at preschool age, such as the child's independence, executive functions and peer friendships. It is also possible that changes in the environment like recovery from depression or healthy paternal care will allow the child to catch up in development, though some treatment studies have failed to document any change in cognitive development (Grace et al., 2003 and Gunlicks and Weissman, 2008). Alternatively there might be a stable relation between maternal depression and infant cognitive ability. If postnatal maternal depression is stable throughout infancy it may be expected to exert a stable influence on infant cognitive abilities. 1.2. Sex differences and change in infant cognitive development Researchers who have claimed early sex differences in cognitive development have argued that boys are more oriented towards objects and systemizing as compared to girls (Baron-Cohen, 2003, Maccoby and Jacklin, 1974 and Spelke, 2005). There are indeed some differences between boys and girls in cognitive development where the boys tend to lag behind girls with several weeks of development. Boys’ depth vision mature later, and boys are generally slower in the emergence of knowledge about moving objects (Kotovsky & Baillargeon, 1998). Moreover, girls seem to have better recall memory when searching for an object in a new place (Piaget's AB-error) as compared to boys (Diamond, 1985). The pointing gesture is emerging earlier in girls, and girls have been found to use gesture–word combinations and two word utterances 3 months earlier than do boys (Özçalýþkan & Goldin-Meadow, 2010). Boys also seem to be more negative, show less interest in social play and need more external scaffolding in emotion regulation, which may leave them less time to explore the world. Girls need less scaffolding in emotion regulation and potentially have more time to spend on cognitive stimulating activities when they interact with their caregivers (Tronick and Reck, 2009 and Weinberg et al., 1999). Even though the boy is performing within the normal range of development it may be more difficult for a depressed mother to meet his enhanced needs for emotion regulation. Therefore boys with a disengaged, depressed mother may be left more alone with their negative emotions. They may require more time in coping and thus give boys less opportunity to take part in stimulating activities as compared to female infant (Grace et al., 2003, Hay et al., 2001 and Murray et al., 1993). The present report originates from a longitudinal study of two groups of infants – one with clinically depressed mothers and a group with non-depressed mothers. The depressed mothers in the present study were offered treatment in the public health system for maternal depression available to all depressed mothers in Norway. This treatment consists of various forms of therapeutic interventions as psychotherapy, medical treatment and/or parent–infant therapy implemented to reduce the impact of maternal depression on children. Nearly all of the depressed mothers took part in some therapeutic interventions (96.2%) and the majority of the depressed mothers took part in parent–infant therapy with their infant (84.6%). In the present study we investigated the relation between change in cognitive abilities during a period of infancy and maternal depression. Since male infants generally tend to lag behind the females a few months in development, infant gender was included in the analysis as a covariate. It was expected that girls would have higher rate of cognitive development as compared to the boys. The few published studies of the effect of maternal depression symptoms on infant cognitive trajectories have reported mixed findings at which age maternal depression symptoms exert greatest influence, throughout infancy (Sutter-Dallay et al., 2011) or in the preschool period (Feldman & Eidelman, 2009). In present study it was expected that infants of clinically depressed mothers at 6 months would show lower cognitive abilities, but that the two groups would become more similar over time.
نتیجه گیری انگلیسی
. Results 3.1. Diagnostic information A total of 57 mother infants-dyads were recruited. As shown in Fig. 1, 29 were recruited to the depression group. Mothers who fulfilled the criteria for a clinical depressive episode when their infants were between 4 and 6 months old, were included in the depression group (n = 27), and two mothers were excluded as they did not fulfill criterion for an ongoing depression disorder. Most of the depressed mothers (70.4%) also received an anxiety diagnosis and four of the mothers with both depression and anxiety disorders also fulfilled the criteria for a personality disorder. Nearly all depressed mothers were under treatment for their depression (96.2%). Most of the depressed mothers took part in parent–infant therapy (84.6%). A total of 28 mother–infant dyads were recruited to the nondepressed group. Two mothers from this group scored above the threshold on CES-D. One was excluded from the study since she were not reachable to schedule the time for assessment at infant age 6 months. The second mother was allocated to the diagnostic interview mentioned above. Thus, a total of 26 dyads participated at the first assessment and all of these mothers scored 13 or lower on the CES-D and constituted the nondepressed group. Infants with birth weight less than 2500 g were excluded from further analyses (n = 3, one from the depression group and two from the nondepressed group). The total sample then consisted of 50 dyads; 26 depressed and 24 non-depressed dyads. In the depressed group there were 13 girls and 13 boys, in the nondepression group there were 12 girls and 12 boys. 3.2. Demographic information and obstetric health history As shown in Table 1, the depressed mothers and the non-depressed mothers were not significantly different in age or in education level (p = .24). Mothers in both groups had overall high level of completed education. The most frequent degree earned among mothers in the non-depressed and the depressed group was Master/PhD degree (50.0% and 42.3%, respectively). Most of the children were living with two parents. There were no significant differences between the infant groups if they had siblings or not (p = .15) or in number of children in the family (p = .48). The majority, 80.8% of the depressed mothers reported to have been mentally ill during pregnancy as compared to none in the non-depressed group. Also, the infants with depressed mothers had significant lower birth weight as compared to infants of non-depressed mothers (t(48) = 3.14, p = 003). Table 1. Between groups comparisons of demographic variables. Non-depressed Mean (SD) (n = 24) Depressed Mean (SD) (n = 26) Statistics Mother age (years) 32.08 (3.64) 32.19 (3.96) t(48) = −.10 p = .92 Education Master/PhD Master/PhD z = −1.176, p = .24 Living with two parents (%) 100 88.5 χ2(1) = 2.95, p = .24 Mental illness during pregnancy (%) 0 80.8% χ2(1) = 33.42, p < .001 Prenatal smoking (%) 0 3.8 χ2(1) = .94, p = .33 Psychotropic medication close to pregnancy (%) 0 7.7 χ2(1) = 1.92, p = .17 Prematurity (<37 GAa week, %) 4.2 11.5 χ2(1) = .92, p = .34 Baby birth weight (g) 3738 (538) 3299 (449) t(48) = 3.14, p = .003 Baby age (days) 192.67 (15.75) 199.50 (26.98) t(48) = −1.08, p = .29 Boys (%) 50 50 χ2(1) = 0.07, p = .79 Baby birth weight (g) 3738 (538) 3299 (449) t(48) = 3.14, p = .003 Siblings (%) 50 26.9 χ2(1) = 2.82, p = .15 Number of children 1.58 1.42 t(48) = .71, p = .48 Mother–infant interaction therapy (%) 0 84.6 χ2(1) = 36.26, p = .00 a GA, gestational age. Table options 3.3. Maternal depression symptoms measured by CES-D One self-report of maternal depressive symptoms was missing at infant age 12 months (due to attrition), and three were missing at 18 months. All missing self-reports stemmed from the depressed group (2 due to attrition and 1 did not return the questionnaire). As expected, the depressed mothers reported significantly more symptoms of depression at 6, 12 and 18 months of age as compared to the non-depressed group (p < .001) (see Table 2). Even though the depressed mothers tended to report lower levels of depression symptoms at the follow-ups as compared to levels reported at infant age 6 months old, they continued on average to report clinical levels of depression symptoms (>18). The non-depressed mothers reported on average low levels of symptoms at all three assessment points. Table 2. Between groups comparisons of CES-D.a CES-Da Non-depressed Depressed Statisticsc [95% CI]d n Mean (SD)b n Mean (SD)b 6 months 24 5.58 (3.17) 26 25.51 (12.55) t(48) = −7.93 *** [.51, .85] 12 months 24 6.33 (3.97) 25 18.96 (12.23) t(47) = −4.75 *** [.28, .68] 18 months 24 6.54 (5.04) 23 18.74 (12.06) t(45) = −4.64 *** [.28, .71] a Center for Epidemiological Studies Depression Scale. b Raw scores of CES-D displayed for easier interpretation. c log10 transformed values are applied in statistic test. d 95% confidence interval. *** p < .001. Table options 3.4. Life stress The depressed and non-depressed mothers reported on average Life Stress below clinical range when the infants were 6 and 12 months old; the depressed mothers reported Life Stress at 6 months mean = 10.24, SD = 7.66 and at 12 months mean = 8.15, SD = 9.46 where as the nondepressed mothers reported mean = 9.04, SD = 7.28 at 6 months and mean = 7.54, SD = 6.90 at 12 months of age. There were no significant differences between the depressed and non-depressed mothers in reported Life Stress at 6 nor 12 months of age (p = .58 and p = .81). 3.5. Maternal parenting style at infant age 6 months Depressed mothers were rated as significantly lower in parenting style (M = 3.03 SD = .74) during play with their 6 moth old infant as compared to the non-depressed mothers (M = 3.85 SD = .54) (t(45.47) = 4.5 p = .000). 3.6. Preliminary analyses of MSEL As shown in Table 3, relations between maternal education, birth weight, maternal parenting style, life stress at 6 and 12 months and MSEL was not significant. Life stress at 6 and 12 months were negatively correlated with maternal education (p = .016 and p = .018, respectively) indicating that mothers with higher education were experiencing less life stress. Maternal education, birth weight, life stress and maternal parenting style were dropped from further analyses of MSEL. Table 3. Correlations between study variables. Study variable 1 2 3 4 5 6 7 1. MSELa 18 months 2. MSELa 12 months .654** 3. MSELa 6 months .216 .233 4. Birth weight .201 .271 .162 5. Maternal educationb .259 .193 −.024 −.146 6. Maternal parenting style .101 .140 .108 .221 .026 7. Life stress 6 months −.222 −.092 .011 .055 −.341* −.036 8. Life stress 12 months −.172 .217 .102 .167 −.355** .014 .573** a MSEL, Mullen Scales of Early Learning Composite Score. b Spearman's rho correlation. * p < .05. ** p < .01. Table options 3.7. Cognitive trajectories As shown in Table 4, the empty model, model 1, showed significant intercept (estimate = 98.07 SE = 1.87) and non-significant linear time coefficient (estimate = −.32, SE = .22). In the second model the quadratic time coefficient was included in the fixed effect, and a linear time coefficient was added to the random effects. Model 2 demonstrated better fit to data as expressed in a lower median AIC than did model 1; it also explained 40% of the total variance in model 1. Since model 2 did not include any covariates it estimated the average growth curve in MSEL. This model indicates that the entire sample, on average, was within the normal range at 6 months of age (estimate = 95.50, SE = 1.53), and that the entire sample, on average, tended to increase their scores on MSEL over development from 6 to 12 months of age as expressed in the “month” parameter (estimate = 2.25 SE = .64), thus performing lower on MSEL over time from 12 to 18 months of age as expressed in the quadratic parameter “months × months” (estimate = −.21 SE = .05). Table 4. Results of longitudinal multilevel modeling predicting MSEL.a Parameter Model 1 Est (SE) Model 2 Est. (SE) Model 3 Est. (SE) Fixed effect Intercept 98.07*** (1.87) 95.50*** (1.53) 100.24*** (2.40) Month −.319 (.22) 2.25** (.64) 1.82** (.71) Month × month −.21*** (.05) −.21*** (.05) Girl −2.49 (2.73) Depression −6.73** (2.72) Girl × month 1.12** (.42) Depression × month −.33 (.42) Random parameters Variance between individuals 42.97* (21.18) 20.25 (16.78) 10.07 (13.87) Variance within individuals 1.01** (.37) .72* (.30) Residual 142.25** (22.48) 89.68** (16.91) 87.37** (16.11) AIC median 1210.870 1184.463 1172.967 a MSEL, Mullen Scales of Early Learning Composite Score; AIC, Akaike's Information Criterion. * p < .05. ** p < .01. *** p < .001. Table options In model 3 maternal depression and infant gender were added as covariates. This model demonstrated a better fit, median AIC was 1172.967, and explained 49.6% of total unexplained variance on level 2 in model 2. Model 3 showed that maternal depression was significantly related to MSEL (estimate = −6.73, SE = 2.72). There was no significant interaction between depression and time, so the prediction of a different time course for infants with depressed mothers was not supported. Since the infants with the depressed mothers had a stable lower MSEL over the follow up as compared to the infants with nondepressive mothers, the estimated decrease in MSEL as expressed in the quadratic parameter “month × month” (estimate = −.21, SE = .05), may be especially severe for infants with depressed mothers, pushing them into the lower normal range of MSEL from age 12 to 18 months. As expected, there was a significant interaction between infant gender and time (estimate = 1.12, SE = .42), indicating that the girls increased more in MSEL from 6 to 18 months as compared to the boys. So boys with depressed mothers seemed to have the lowest trajectories in MSEL over the follow-up.