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Abstract To separate effects of maternal depression on infant cognitive versus language development, 1-year-olds were assessed using the revised Bayley Scales of Infant and Toddler Development (BSID-III). Percentile scores on the Bayley Expressive Communication (EC) subscale were significantly negatively correlated with maternal self-report scores on the Beck Depression Inventory (BDI-II). However, mothers’ BDI-II scores did not correlate with infant percentile scores on the general cognitive (COG) or receptive communication (RC) subscales. Boys had significantly lower percentile scores than girls on the RC and EC scales, but did not differ on the Cog scale. Gender and maternal depression did not significantly interact on any of the scales. These findings suggest problems with expressive communication precede, and may at least partially account for, apparent deficits in general cognitive development.

1. Introduction Maternal depression in the postpartum period, either by itself or in conjunction with other factors such as child gender, the presence of contextual risk, or the chronicity and timing of the mother's depression, has been linked to multiple effects on child cognitive and linguistic development (Coghill et al., 1986, Feldman and Eidelman, 2009, Grace et al., 2003, Hay and Kumar, 1995, Kurstjens and Wolke, 2001, Murray et al., 1993, NICHD, 1999, Petterson and Albers, 2001, Sohr-Preston and Scaramella, 2006, Sutter-Dallay et al., 2011 and Whiffen and Gotlib, 1989). These effects have been most often attributed to disruptions in depressed caregivers’ ability to support or “scaffold” infant state and behavior, with resulting deficits in infants’ extraction of information about environmental contingencies (e.g., Hay, 1997). However, beyond effects on general cognitive processes, recent research has suggested that parents scaffold pre-linguistic infants’ speech perception and rudimentary language development to an extent not previously recognized (Kuhl, 2007). If so, then in cases in which such scaffolding is likely disrupted – as in postpartum depression (Bettes, 1988) – early effects on infant communicative development, separate from effects on general cognitive development, may be observable. In fact, because in some earlier assessments measures of cognitive development were heavily dependent on infant communicative skills, effects that have been attributable to delays in cognitive development may instead be partly or wholly attributable to delays in language development. The purpose of the present paper is to report such findings. The evidence for effects of maternal depression on infant communicative development comes both from laboratory-based studies on pre-linguistic infants and outcome studies focused on infancy, the toddler years, and beyond. Caregivers support infant communicative development in a number of ways, including through the quantity and quality of vocal stimulation they provide, along with the extent to which it is contingent on infant behavior (Huttenlocher, Haight, Bryk, Seltzer, & Lyons, 1991; Rollins, 2003). For example, a child's developing vocabulary is predicted to some extent by the amount and complexity of language stimulation the mother gives (Gleitman, Newport, & Gleitman, 1984; Hart & Risley, 1995; Huttenlocher et al., 1991). In addition, when addressing infants, parents tend to exaggerate changes in vocal pitch, hyperarticulate vowels, and produce slowed, simplified, and repetitive utterances (Fernald, 1984). Evidence indicates that this infant-directed speech (IDS) is especially effective at promoting important foundational processes for pre-linguistic infants, including phoneme discrimination (Liu, Kuhl, & Tsao, 2003), word segmentation (Thiessen, Hill, & Saffran, 2005), word learning and memory (Ma et al., 2011 and Singh et al., 2009), and the detection of phrase boundaries (Jusczyk et al., 1992). Consistent with the hypothesis that IDS highlights key aspects of linguistic stimuli for the infant, mothers of 1-year-old infants who produce IDS with relatively greater pitch modulation also report their children have higher concurrent productive vocabulary (Porritt, Zinser, Bachorowski, & Kaplan, 2014). More broadly, recent evidence suggests that the volume of infant-directed speech in the home environment has an effect on the efficiency of child language processing, with resulting effects on the rate of language growth (Weisleder & Fernald, 2013). However, depressed mothers exhibit differences relative to non-depressed mothers in the pitch characteristics, linguistic content, degree of contingent delivery, and degree of infant focus in their speech (Bettes, 1988, Breznitz and Sherman, 1987, Herrera et al., 2004, Murray et al., 1993, Porritt et al., 2014, Reissland et al., 2003 and Zlochower and Cohn, 1996). Thus, there are clear deficits in the kinds of maternal behavior thought to promote rudimentary language development, and these may be a root cause of later delays in vocabulary development. Consistent with the language-promoting effects of infant-directed speech, some evidence suggests a delay in the “perceptual commitment” to the parents’ native language for infants of depressed mothers. Whereas infants typically exhibit the ability to discriminate non-native phonemes at 6 months, but lose this ability toward the end of the first year as they commit to their native language (Werker & Lalonde, 1988), infants of depressed mothers showed poor discrimination of non-native phonemes at 6 months, but better-than-normal discrimination of non-native phonemes at 10 months (Weikum, Oberlander, Hensch, & Werker, 2012). Direct links have been established between native speech sound discrimination and later word learning (Tsao et al., 2004 and Werker and Yeung, 2005). Interestingly, infants of mothers who had taken selective serotonin reuptake inhibitors (SSRIs) during gestation showed an opposite effect: faster commitment to the native language, possibly attributable to neurochemical acceleration of brain development (Weikum et al., 2012). Taken together, this research suggests that delays in language development may start very early in the lives of infants of depressed mothers, and highlights some potential behavioral mechanisms. Although not specifically tied to the ways in which mothers talk to their infants, delays in language development have been observed in several large-scale outcome studies with children of depressed mothers. For example, the NICHD Early Child Care Research Network (1999) followed a large sample of mothers and infants at 6, 15, 24, and 36 months, and assessed general cognitive and language development at 36 months. After demographic risk factors had been taken into account, relative to infants whose mothers had no epochs with elevated self-report scores of depression, children of mothers with chronically or occasionally elevated depression scores not only performed more poorly on an assessment of “school readiness” – which included items on color recognition, letter identification, number/counting skills, comparisons, and shape recognition – but also on a measure of verbal comprehension and expressive language. Expressive language scores were lower for children of mothers with chronically elevated than occasionally elevated scores. Possibly related to maternal scaffolding of infant language development as outlined above, these differences were mediated by ratings of maternal sensitivity coded from separate play sessions averaged across the 4 multiple assessment ages. Similar outcomes were reported by Stein, Malmberg, Sylva, Barnes, and Leach (2008), who performed a longitudinal study on the effects of maternal depression on child language development at 36 months, with an explicit focus on the roles of parenting and socio-demographic risk factors. Structural equation modeling suggested that maternal depressive symptomology had an indirect effect on language development, and that the pathway was through the negative effects of depression on the quality of the mother's early observed caregiving. The negative effect of elevated maternal depressive symptoms on caregiving was stronger for socioeconomically more disadvantaged families, but there was no moderating effect of SES on the path between caregiving and language. Several smaller studies have yielded similar conclusions. For instance, Milgrom, Westley, and Gemmell (2004) reported that 42-month-old children of mothers who had been treated as inpatients for major depression in the perinatal period had significantly lower full-scale WPPSI-R scores (but not Verbal IQ) and significantly lower cognitive and language scores on the Early Screening Profile relative to controls. The outcomes on cognitive-linguistic development were mediated by observation-based assessments of maternal responsiveness obtained at 6 months postpartum, after the mothers’ acute depressive episodes had remitted. These studies are consistent with the hypothesis that depression leads to deficits in the quality of maternal parenting behavior, which in turn contributes to poorer language development, possibly via general effects of enrichment on cognitive development, but also possibly due to specific effects on the quantity and/or quality of maternal vocal input. Given the evidence for very early effects of maternal stimulation of rudimentary language processing, an important question is how early during development the effects of maternal depression on infant language development can be detected. However, very little data exists on this point (Azak, 2012). Cornish et al. (2005) reported that mothers who self-reported chronically elevated, but not briefly elevated, symptoms of depression had children with lower scores on the BSID MDI and Psychomotor Development Index (PDI) at 15 months. However, there were no detectable differences attributable to maternal depression on receptive or expressive language, as assessed through an interviewer-completed scale based on mothers’ responses to structured questions at 12 months. In attempting to explain this discrepancy, the authors cite the relatively high SES of their sample, the use of maternal reports, and the possibility that effects may be delayed. There may be another explanation. Many items from the BSID-I and -II that form the basis for the MDI directly reflected language development (Bayley, 1969, Bayley, 1993 and Bayley, 2006). Perhaps the lower MDI scores among infants of chronically depressed mothers were driven, in whole or in part, by a delay in language development – a delay not detected by responses to structured interview questions completed by depressed mothers of 12 month olds. Similarly, prior effects of maternal depression on child cognitive development using the BSID-I or -II (e.g., Lyons-Ruth et al., 1986, Murray et al., 1996 and Whiffen and Gotlib, 1989) may be at least partially attributed to effects on language development. Interestingly, in a recent study on the relation between child language skills and the development of concern for others, an initially significant correlation between BSID-II general cognitive ability and concern for others was no longer significant when early language skills, as assessed separately from the BSID-II, were taken into account (Rhee et al., 2013). If the language-laden nature of the BSID-II MDI masked early effects of maternal depression on language development in infants, the third revision of the Bayley scales (BSID-III) might provide the sensitivity necessary to detect language delays. This is because in the BSID-III language-based items were removed from the MDI, and infant mental developmental status was partitioned into a three-scale structure: A Cognitive Scale (Cog), which has reduced reliance on the child's language ability relative to the BSID-I or -II, and a two-part Language Scale, which separately assesses Receptive Communication (RC) and Expressive Communication (EC). Many of the language-based items that were removed from the BSID-II MDI were subsequently incorporated into the RC and EC BSID-III scales. The current report describes an analysis of the effects of maternal depression on early cognitive-linguistic development using the BSID-III. We predicted that 1-year-old infants of mothers with elevated symptoms of depression would demonstrate delays in communicative development, but not necessarily in general cognitive development

. Results 3.1. Demographic and diagnostic information Information concerning demographic and depression self-report information for the 91 mother-infant dyads recruited to the study is presented in Table 1. Thirty mothers had elevated scores on the BDI-II (BDI-II > 13; 33.0%), and 61 had non-elevated scores (BDI-II ≤ 13). Within the “elevated’ group, 18 scored in the “mild” range (BDI-II = 14–19); 9 scored in the “moderate” range (BDI-II = 20–28); and 3 scored in the “severe” range (BDI-II = 29–63). Because of relatively small numbers in the moderate and severe categories, those two categories have been combined below. Mothers with elevated BDI-II scores (BDI-II > 13) were significantly less likely to be married than mothers with non-elevated BDI-II scores (z = 2.15, p = .05). Fourteen of 91 mothers reported that they were currently taking anti-depressant medication, including 8 with BDI-II scores in the “non-elevated” range, 4 with scores in the “elevated/mild” range, and 2 with scores in the “elevated/moderate-to-severe” range. Table 1. Maternal demographic and self-report depression data. Variable BDI-II ≤ 13 BDI-II > 13 N 61 30 Age of mother (yrs) 30.0 (4.6) 29.3 (6.3) Age of infant (days) 365.9 (31.2) 362.4 (31.1) Infant gender (♀/♂) 36/25 14/16 Ethnicity White 42 (68.9%) 16 (53.3%) Latina 11 (18.0%) 9 (30.0%) African-American 4 (6.6%) 2 (6.7%) Asian 3 (4.9%) 1 (3.3%) Native-American 1 (1.6%) 2 (6.7%) Marital status Married 51 19 Unmarried 10 11 Mother's education 5.7 (1.4) 5.2 (1.3) Family income 6.5 (2.0) 5.7 (2.7) Number of children 1.7 (1.0) 2.1 (1.1) Table options 3.2. Bayley Scales of Infant and Toddler Development (BSID-III) Percentile data for the BSID-III (Cog) subscale were available for 91 infants. Data for the RC and EC subscales were available for only 80 of these, because 11 of them became fussy as the assessment progressed and did not complete the items on which those subscales were based. 3.2.1. 3.2.1. Demographic variables and BSID-III scales Table 2 presents a correlation matrix showing the relations between BSID-III scales and demographic variables. Bayley Cog percentiles were unrelated to mother's age, education, family income, marital status (contrast coded as 1 = married; −1 = unmarried), minority status (contrast coded as 1 = ethnic minority; −1 = white), number of children, infant gender, and current anti-depressant medication use. Bayley RC and EC percentiles were similarly unrelated to all demographic variables, except for a negative correlation with number of children, and an effect of gender. Table 3 presents mean percentile scores as a function of infant gender. Collapsed across BDI-II categories, means were higher for girls than boys for each BSID-III subscale. Table 2. Correlations between Bayley scales and demographic variables. 1 2 3 4 5 6 7 8 9 10 11 12 1. Bayley Cog – .41** .20 −.09 −.08 .10 −.02 .02 −.10 .00 .06 .13 2. Bayley RC – .36** −.03 .11 .14 −.16 .20 −.25* −.21 .03 .12 3. Bayley EC – −.21 .02 −.09 .10 .10 −.24* −.33** −.31** −.03 4. Mother Age – .28** .42** −.25* .34** .07 .25* −.05 .04 5. Mother Educ – .45** −.28** .39** −.17 −.32** −.15 .10 6. Family Income – −.58** .63** −.19 −.08 −.23* −.03 7. Minority Status – −.51** .16 .20 .17 .06 8. Marital Status – −.15 −.09 −.28** .02 9. Infant Gender – .30** .14 −.01 10. # Children – .27** −.05 11. BDI-II score – .10 12. Medication – * Signifies p = .05. ** Signifies p = .01. Table options Table 3. Mean Bayley subscale percentile scores (with standard deviations) as a function of infant gender and BDI-II category. n Cog RC EC Girls Non-elevated 29 .644 (.269) .448 (.223) .558 (.180) Mild 9 .775 (.241) .580 (.296) .591 (.225) Moderate/severe 5 .542 (.198) .314 (.197) .374 (.155) Total .660 (.260) .460 (.243) .543 (.194) Boys Non-elevated 22 .554 (.208) .303 (.224) .489 (.271) Mild 9 .573 (.310) .341 (.312) .466 (.198) Moderate/severe 6 .577 (.404) .417 (.336) .187 (.132) Total .562 (.263) .331 (.262) .434 (.258) Table options 3.2.2. Maternal mood and BSID-III scores Table 2 presents first-order correlations between BDI-II scores and percentile scores on the three BSID-III scales. BDI-II scores were significantly negatively correlated with Bayley EC scale percentiles, r(80) = −.31, p = .01, but did not correlate significantly with Cog or RC scale percentiles (p's > .10). The relation between BDI-II category and Bayley EC percentiles was further examined using a hierarchical linear regression, in which child gender, number of children, and a gender × BDI-II category interaction term were entered into the equation in steps 1–3, followed by BDI-II category in step 4. Table 4 shows that infant gender and number of children, but not the gender × BDI category interaction term, were associated with significant increments in R2 in steps 1–3. However, after demographic variables had been taken into account, a mother's BDI-II category accounted for a significant further increment in the proportion of variance accounted for in infant EC percentiles, ΔR2 = .056, F(1, 75) = 5.12, p = .05. Table 4. Hierarchical linear regression of infant gender, number of children, gender × BDI-II category interaction, and BDI-II severity category on Bayley expressive communication (EC) percentiles. Model 1 Model 2 Model 3 Model 4 Variable B SE B β B SE B β B SE B β B SE B β Gender −5.45 2.53 −.24* −3.40 2.58 −.15 −2.18 4.42 −.10 −2.41 4.31 −.11 # Children −6.05 2.44 −.28* −5.97 2.46 −.28* −4.50 2.48 −.21 Gender × BDI −0.09 2.67 −.07 −0.75 2.60 −.05 BDI category −7.78 3.44 −.25* R2 .056 .126 .127 .183 F for ΔR2 4.64* 6.16* 0.11 5.12* * p = .05.