One environmental factor that has been long associated with TD in the offspring is parental communication deviance (CD; Singer & Wynne, 1965a; Singer & Wynne, 1965b; Wynne, et al., 1977; Wynne, 1984; Wynne & Singer, 1963a, 1963b). CD refers to a form of intrafamilial communication that is vague, fragmented, and
contradictory and that compromises the development and sharing of meaning between parent and offspring (Wynne, 1981).
Initially developed by family therapy researchers Lyman Wynne and Margaret Singer, CD was contextualized as a broad set of communicational and linguistic disturbances (Singer & Wynne, 1966). Exposure to this style of intrafamilial communication was hypothesized to have a pervasive impact on the offspring’s developing cognition, leading to TD (Wynne, 1984).
Since its initial conceptualization, the association between CD and psychosis in offspring has been independently replicated in many studies (de Sousa, Varese, Sellwood, & Bentall, 2013). However, only a few studies have looked into the
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specific association between CD and TD and none as adequately controlled for comorbid psychotic symptoms.
In one of their earliest studies Wynne and Singer had been able to blindly predict severity of offspring’s TD from the parents’ test data (p< .001) suggesting some degree of symptom specificity (Singer & Wynne, 1965b). Since then, other studies have also found significant associations between maternal and psychotic offspring’s degree of CD (Velligan, et al., 1995) or between maternal thinking disturbance and offspring’s TD (Harrow & Quinlan, 1985; Johnston & Holzman, 1979; Shenton, et al., 1989; Tompson, et al., 1997).
Sass and colleagues (1984) tested parents of psychotic offspring with different degrees of TD using both TAT cards (Murray, 1943) and a descriptive task (d-task)8. The researchers reported that parents of highly thought-disordered offspring had significantly higher CD scores regardless of whether they were compared to parents of controls or to parents of non-thought disordered psychotic offspring.
Unfortunately, Sass and colleagues’ study had three significant limitations: the sample size was small, TD was not measured directly in the offspring and the analyses of the data did not consider comorbid psychotic symptoms.
In another study, Rund (1985, 1986; Rund & Blakar, 1986) tested parents using both TAT cards and a communication conflict situation (CCS) in which the family members have to jointly find their way through a map with conflicting routes. When the author analysed the data, the sharpest contrast found was between parents of paranoid and non-paranoid participants, with the latter group displaying
significantly more CD. A high proportion of the participants in the non-paranoid group had been diagnosed with disorganised schizophrenia, a subtype whose
8 In this task, parents were invited to explain concepts of the American culture as if they were talking to
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prominent characteristic is TD and behavioural disorganisation. Unfortunately, and despite utilizing a robust multi-method design, Rund did not measure TD directly so no firm conclusions about the specificity of CD for TD can be drawn from the findings.
In a seminal study, Wahlberg and colleagues (1997) looked at the interaction between genetic-risk and CD in the prediction of TD. The design of the project was especially relevant as it allowed for the disentanglement of genetic effects given that
CD was measured in the adoptive family of high- and low-risk adoptees (High- and
low-risk status was determined by the presence or absence (respectively) of psychotic-spectrum diagnosis in the biological mother). Interestingly, the authors reported that it was the interaction between CD in the adoptive parent and the high- risk status of the adoptee that best predicted TD. More importantly was the fact that low CD in the adoptive parents of high-risk adoptees predicted low TD, suggesting that low CD may have a protective effect on the offspring’s cognition.
In a later study, Wahlberg and colleagues (2000) replicated the same findings with the same sample but now using the thought disorder index (TDI; Johnston & Holzman, 1979). In this study, adoptees were on average 21 years of age at follow-up. Again, the authors reported a significant interaction between CD in the adoptive parent and adoptee’s high-risk status predicting idiosyncratic verbalisation score (OR= 1.70; CI 95%[1.05; 2.76]; p= .03).
Metsänen and colleagues (2007) tested the adoptees from this Finnish cohort with a 12-year interval using the TDI (Johnston & Holzman, 1979). The average of adoptees’ age at follow-up was 33. At index assessment 40.9% adoptees with high TDI scores had adoptive parents with equally high levels of CD as opposed to 19.4% of the adoptees who had been raised by adoptive parents low on CD (p= .04). At
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follow-up, CD worked only as a predictor of TD in low-risk adoptees meaning that low-risk adoptees raised by adoptive parents with high-levels of CD were more likely to have high TDI scores at follow-up and this difference was statistically significant. Surprisingly, CD did not predict increased TDI scores in the high-risk adoptees at follow-up.
In the discussion, Metsänen and colleagues argue that the unexpected results of the high-risk adoptees at follow-up could have been the consequence of a change in the environment (e.g. leaving the adoptive family’s home). In Wahlberg and
colleagues (1997) study, high-risk adoptees, when raised by parents with low CD, displayed lower TD suggesting that high-risk adoptees may be more sensitive to a change of environment. It may as well be that unmeasured environmental variables may have acted as important moderating factors. For example, Horan, et al. (2006) found a significant negative correlation between TD and smaller network size (r= - 0.36, p< .05) in a sample of patients diagnosed with schizophrenia.
Finally, Roisko and colleagues (2014), using data from the same Finnish cohort (adoptees were in their thirties), reported again significant associations
between adoptive parent’s CD and offspring’s TD (p= .009). More importantly, CD
did not predict diagnoses of psychotic-spectrum disorders suggesting some specificity that has been argued by the same authors in a recent meta-analytical review (Roisko, Wahlberg, Miettunen, & Tienari, 2014).