Content and style of speech from mothers with schizophrenia towards their infants

Abstract

Schizophrenia can affect verbal communication and relational processes, but how it might disrupt maternal infant-directed (ID) speech is unknown. Maternal speech characteristics were coded, blind to clinical information, from brief videotaped mother–infant interactions of 14 mothers with schizophrenia and 36 mothers with similar hospitalisation but with other clinical diagnoses. Compared with the non-schizophrenia group, the speech of mothers with schizophrenia was less infant-focused. Infant-focused content was also predicted by maternal age, but not by duration of hospitalisation or infant gender. Mothers with schizophrenia also used significantly fewer songs or rhymes than the comparison group, and showed a trend towards fewer negative comments. Speech prosody/content deviations were rarely observed in either group, and no differences were found in speech rate or structure. The marked lack of ID speech content of mothers with schizophrenia reflects low maternal sensitivity, perhaps due to ‘theory of mind’ impairment and blunted affect, and may contribute to the early developmental vulnerability of their children.

Introduction

Schizophrenia is a chronic psychotic disorder with a low prevalence; however, most women with schizophrenia will become mothers (McGrath et al., 1999). Compared with well mothers and mothers with other mental disorders, mothers with schizophrenia are less responsive, more self-absorbed and more remote when playing with and feeding their infants (Goodman, 1987, McNeil et al., 1985, Näslund et al., 1985, Persson-Blennow et al., 1986), even following clinical recovery (Riordan et al., 1999, Wan et al., 2007). Mothers with schizophrenia tend to lack verbal communication with their infants (e.g. Riordan et al., 1999, Persson-Blennow et al., 1984), but little is known about the content and style of their talk.

Studies of infant development emphasise the importance of infant-directed (ID) speech, or motherese, for regulating infant arousal and attention, and for supporting cognitive development and language acquisition (Kaplan et al., 1996, Lacroix et al., 2002, Murray et al., 1993, Paavola et al., 2005, Tomasello and Farrar, 1986). ID speech is an adapted speech register, widespread across cultures, involving short, simple utterances (high repetition and semantic continuity) in a heightened pitch, with high infant-focused content, a high frequency of questions and directives, and a low frequency of declaratives (Gleitman et al., 1984, Tomasello et al., 1986). Maternal singing, which also has infant-directed features, increases infant attention and responsiveness to the mother (de l'Etoile, 2006, Nakata and Trehub, 2004). Maternal mental health is highly likely to affect the infant-directedness of speech. Depressed mothers vocalise less frequently (Breznitz and Sherman, 1987), with speech content that is less infant-focused and more negative than in healthy controls (Cohn et al., 1990, Herrera et al., 2004, Murray et al., 1993). Exposure to this low ID speech has been reported to account for the poorer learning and cognitive functioning of infants of depressed mothers (Kaplan et al., 2002, Kaplan et al., 2004, Murray et al., 1993).

As schizophrenia is associated with vocal emotion processing impairments (Hooker and Park, 2002, Kucharska-Pietura et al., 2005), the ID features of maternal speech may be particularly disrupted by schizophrenia compared with other forms of mental disorder. ‘Theory of mind’ impairments may also be a contributory factor (Brűne, 2005) and persist after clinical remission (Inoue et al., 2006). The infants of mothers with schizophrenia constitute a particularly vulnerable group due to a complex interaction of genetic and environmental factors (c.f. Niemi et al., 2003); thus, exposure to markedly poor maternal speech in early infancy may exacerbate developmental risk. For example, Wahlberg et al. (2004) reported that children of mothers with schizophrenia who were adopted away were at elevated risk of developing thought disorder only when the adoptive parents showed highly disorganised verbal communication.

The current study compared the speech style, speech content, and singing of mothers with schizophrenia with the same characteristics in a non-schizophrenia clinical group of mothers, with comparable illness severity and current hospitalisation. We hypothesised that, compared with mothers admitted with diagnoses other than schizophrenia, mothers with schizophrenia: (i) will speak less, and use shorter utterances to their infants; (ii) will have less infant-directed speech in style (less repetition, less semantic continuity, less infant-directed syntax, more abnormal) and content (less infant-focused, more negative, with fewer songs and rhymes). Where ID speech was found to be poorer in mothers with schizophrenia, we were interested in whether the effect would be confounded by hospitalisation duration, maternal age, or infant gender.