We have conducted a rigorous community-based cross-sectional study, frequency-matched on gender, birth year and birth order to investigate the home nurture environmental factors for autistic traits in China. Overall, the results from the study suggested that poor home nurture environment, including insufficient language/cognition stimulation, undesirable parental warmth and poor physical living environment may place preschool children at a great risk for autistic traits. We will discuss each of these findings in turn and address the implications of these findings.
We found that frequent language/cognition stimulation, which means the quality of verbal and cognitive information a caregiver provides to a child was significantly associated with autistic traits. In other words, children with higher levels of autistic traits reported by caregivers had more difficulty on language interaction. The variability in child language in the early years is well-established. Positive characteristics such as high maternal vocabulary level and high socio-economic status have advantageous impact on children’s language and cognitive development. One previous research also demonstrated that poorer child language development predicted more autistic traits. It is hypothesized that the identified association between autistic traits and language and cognitive stimulation may be explained by two key pathways. Firstly, there is a relationship between early language and later autistic traits, which is comparatively to the interaction with caregivers. Therefore, caregivers did not give children enough response and less opportunities on verbal and cognitive information, children with autistic traits themselves has deficiency on capability for self-explanation and communication, and as a result, the symptom would also be more obvious. Alternatively, it has been reported that the shared genetic influences of children and caregivers may be responsible for the overlap in linkage signals reported in molecular genetic studies of language skills and autistic traits.[31, 32] Caregivers themselves had defect on communication skills, and therefore decrease the stimulation of language at home environment. Although this finding need to be replicated before any firm conclusions can be mad, it raises the possibility that early interventions in terms of language and cognitive skills by caregivers may reduce the occurrence of autistic traits.
Previous research has demonstrated parental warmth an indicator of parents’ love and acceptance of the child which was associated with children’s better mental health and psychological adjustment, as well as lower levels of child behavior problems. Studies examining warm affect, positive cooperation and communication showed negative associations with conduct problems and high levels of emotional symptoms.[35, 36] In our study, we found parental warmth a protective factor for autistic traits. Generally speaking, if a child did not experience consistent warmth from a parent, his own positive emotional responsiveness to the parent might decrease. Likewise, if a parent found that their attempts at warmth were not reciprocated, the frequency of their displays of warmth would also decrease over time. Preschool children with high levels of autistic trait were preceded by early manifested ASD-like problems in infancy and toddlerhood. Thus, favorable parental warmth and considerate care in early childhood are needed in an attempt to diminish further derailment of the child’s behavior and development, and to prevent the autistic traits or related externalizing problems. However, it is yet to be established whether interventions targeting particular aspects of parental warmth or other parenting behaviors can be effective in driving more change in children with high levels autistic traits or if such interventions can directly reduce autistic traits, which are both questions we hope to examine in future studies.
The home physical environment not only affects individual child well-being, but also is an important pathway through which socio-economic inequalities create child health and developmental disparities. Unstable home physical environment has negative effects on children’s health and development. One possible reason proposed for the negative effects of poor physical environments on child behavior problem is through increased exposure to stress.[39, 40] Biological changes are likely to occur if the body is exposed to chronic stress (repeated stress response over time), resulting in dysfunction of the neuroendocrine and immune systems. These systems might be particularly sensitive during the formative years of childhood. Dysfunction of children’s neuroendocrine, in turn, is associated with cognitive and socio-emotional outcomes. Children with autistic traits have lower neuropsychological performance  and impairment in social function.[11, 44] And as a result, terrible home physical environment may make their symptoms more apparent.
All of these findings should be interpreted in the context of several study limitations. First, there are clear limitations with using a tool of this type to measure home nurture environment. It relies on the observation and perceptions of parents, who may not be entirely objective. Second, because we did not assess other emotional or behavioral problems, we could not rule out the possibilities that other comorbid conditions may have contributed to the significant associations between autistic trait and home nurture environment reported in this study. In addition, the study was limited to only six schools in one city, with obvious issues of representativeness for the wider population.