Many programmes study the infant siblings of children with autism? What are the limitations and ethical considerations related to this approach? Do they outweigh the benefits?
Introduction
Studying infant siblings of children with autism (SIBs-A) offers valuable insights into early developmental trajectories and contributes significantly to earlier diagnosis, more effective interventions, and a deeper understanding of autism (Gangi et al., 2021; Jones et al., 2014; Manzini et al., 2021; Newschaffer et al., 2012; Zwaigenbaum et al., 2015). These children, often considered at heightened genetic risk, provide a unique opportunity to identify early behavioural, neurological, and biological markers before the onset of clear symptoms (Manzini et al., 2021). Consequently, many studies recruit infants prenatally or from as early as 4 to 6 months of age and follow them through to 24 or 36 months (Gangi et al., 2021; Landa et al., 2012; Manzini et al., 2021; Newschaffer et al., 2012; Szatmari et al., 2016), at which point a comprehensive, multidimensional developmental profile is established.
The growing body of literature (mentioned above and will be cited below) strongly suggests that infants who are later diagnosed with autism often display behavioural traits early in life. A significant number of these children—particularly those who are infant siblings of children with autism (SIBs-A)—exhibit signs of future autism as early as six months, and more consistently by twelve months of age. This paper critically reviews the limitations of such research, including methodological challenges, variability in findings, and the potential risk of misdiagnosis. It also considers important ethical concerns, such as increased parental anxiety, issues around informed consent, and the psychological impact of labelling infants as ‘at risk’ (Landa et al., 2012; Manzini et al., 2021; Szatmari et al., 2016). Nonetheless, this paper takes a clear stance: the substantial benefits of SIBs-A research—particularly its potential to enhance early detection and guide timely support—justify its continuation. With appropriate ethical safeguards in place, these studies offer a valuable opportunity to improve both clinical outcomes and family experiences.
Literature Review
The word “autism” was first used by Eugen Bleuler, a Swiss psychiatrist, in 1911. Bleuler introduced the term “autistic thinking” to describe a symptom of schizophrenia, where individuals seemed withdrawn into their own inner world and detached from reality (Evans, 2013). The term comes from the Greek word “autos”, meaning “self”. Later in 1943, Leo Kanner used the term in a more specific way to describe a group of children with unique social, communication, and behavioural characteristics. He published a paper titled “Autistic Disturbances of Affective Contact” (Leo Kanner, 1943) and is credited with identifying Autism as a distinct neurodevelopmental condition. Almost fifteen years later from Kanner’s paper, another paper (Pearson & Kley, 1957) published to emphasise the particular abnormalities of behaviours have tendency to run in families. Yet, the first studies appeared about the infant siblings of autism (SIBs-A) in 1980s (Newschaffer et al., 2012). Since then, the number of papers on autism has grown exponentially about SIBs-A to identify early biomarkers, aiming to develop a more objective diagnosis (Landa et al., 2012).
There is extensive research scrutinising the aetiology, i.e. cause or reason, of autism and they sign that genetic mechanism and environmental reasons are the main contributors of this condition (Newschaffer et al., 2012). Particularly importance of prenatal period and impact of environment on that period is immense. The primary goal of most of that research cited above is to enable early prognosis prediction and guide individualized intervention strategies for families with young infants (Manzini et al., 2021; Szatmari et al., 2016).
Derived from their review, Szatmari et al., (2016) suggested that studies of SIBs-A were driven by two key findings: the strong familial link suggesting increased risk for siblings, and the significant delay between the emergence of parental concerns (often around 12–18 months) and the average age of diagnosis (typically 4–6 years), a gap that often causes substantial parental distress. A common consensus among those mentioned above and many other studies is that autism have strong genetic aspect and approximately 20% of these high-risk siblings are diagnosed with autism by around 36 months of age. Or these siblings might develop more subtle form of autism called ‘broad autism phenotype’ (Ben-Yizhak et al., 2011). The Broad Autism Phenotype (BAP) refers to a set of mild traits or characteristics that are similar to, but less severe than, those seen in individuals with autism. According to (Hurley et al., 2007) these traits are often found in biological relatives (especially parents or siblings) of individuals with autism. Common Features of BAP might Include: Social difficulties (e.g., being socially reserved or awkward); Communication differences (e.g., flat intonation, less use of gestures); Rigid or repetitive thinking styles; Strong attention to detail or routines.
When it comes to autism social communicative behaviours the social brain phrase is commonly used in neuroscience. The social brain refers to a network of brain regions responsible for processing social information, such as facial expressions, emotions, and others’ thoughts and intentions (Johnson et al., 2005). Key areas include, the amygdala, medial prefrontal cortex, superior temporal sulcus, and fusiform face area (Adolphs, 2003). In individuals with autism, some of these regions may function differently, which can contribute to challenges with eye contact, emotion recognition, and understanding others’ perspectives. These differences help explain some of the social communication difficulties commonly associated with autism (Szatmari et al., 2016). Yet, it is not clear whether human infant is already born with social brain functions or it is product of development. Findings of (Johnson et al., 2005) suggest that ‘whole social brain network is partially active from at least 3 months…’(p.10). Another study (Tzourio-Mazoyer et al., 2002) suggets that at around 2 months of age, a key shift occurs in human face processing, as infants begin to recognize faces based on the configuration of internal facial features. The review of Szatmari et al., (2016) underlined that high-risk (HR) infant sibling work in autism design has created an understanding that autism often, but not always, begins to emerge between 6 and 18 months, with early signs affecting social communication. These and similar studies increase the hope for the early studies with the babies to detect early signs of autism in SIBs-A, especially in social brain aspect.
To scrutinise trajectories of development i.e. language, motor and nonverbal cognitive functioning, studies followed children between 4 or 6 months to 36 months of age (Landa et al., 2012). Landa and colleagues investigated the diverse developmental paths of infant siblings of children with autism spectrum disorder (ASD), who are at higher genetic risk for ASD and related impairments. Utilizing latent class analysis on data from 204 high-risk siblings assessed between 6 and 36 months, they identified four distinct developmental trajectory classes: class 1- Accelerated Development: This group, comprising 25.7% of the sample, exhibited advanced developmental progress and predominantly included children without ASD. Class 2- Normative Development with Above-Average Nonverbal Outcomes: Representing 40.0% of the sample, these children followed typical developmental patterns and achieved above-average nonverbal cognitive outcomes. Class 3- Receptive Language and Motor Delays: Accounting for 22.3% of participants, this class showed delays specifically in receptive language and both gross and fine motor skills. Class 4- Widespread Delayed Skill Acquisition: The smallest group, at 12.0%, demonstrated broad developmental delays, with declining trajectories over time.
Notably, children later diagnosed with ASD were distributed across the second, third, and fourth classes, indicating variability in early developmental patterns among those who develop ASD. The study underscores that early delays in receptive language and motor development can occur in high-risk siblings regardless of an eventual ASD diagnosis. It also highlights that many non-ASD high-risk siblings display average or accelerated development, suggesting that early motor, language, and cognitive trajectories may be independent of social and communication delays observed in some high-risk children. This study (Landa et al., 2012) clearly indicate that developmental regression, particularly in language and communication area, is a case in many children (between 10.6% and 38.6%) later diagnosed with autism. In the same vein, abnormal development is seen in the first fifteen and sixteen months particularly in social, communication and motor development (Ozonoff et al., 2010). Both of these studies (Landa et al., 2012; Ozonoff et al., 2010) suggest that behavioural signs of autism are not present at birth but develop gradually through a reduction in key social communication behaviours during the early infancy. This is consistent what Johnson and his colleagues (Johnson et al., 2005) indicated.
Benefits of Studying the Infant Siblings of Autistic Children
Zwaigenbaum et al. (2015) emphasize the critical importance of early autism detection, which can enable timely, evidence-based interventions and significantly improve long-term developmental outcomes. This is particularly relevant for families with older children with autism. Early identification not only facilitates access to specialised support but also alleviates the uncertainty that many families experience before a formal diagnosis is made (Szatmari et al., 2016).
Based on over thirty years of professional experience, the author of this paper has observed from her first-hand experience many parents of autistic children are quick to recognise similar traits in their younger children. Importantly, these families are often less concerned with labelling and more focused on accessing the right support at the right time. Advancements in prospective studies and the development of innovative technologies have greatly improved our understanding of autism’s early emergence in children under 24 months (Zwaigenbaum et al., 2015; Landa et al., 2012(Szatmari et al., 2016). This study findings should be put into practice provide early support to those children and their families.
To consolidate this growing knowledge, Zwaigenbaum and colleagues assembled a multidisciplinary panel that reviewed the literature and reached a consensus on reliable early indicators for autism. Their key recommendations, which could be integrated into healthcare systems like the NHS, include:
- Conducting regular screening at local child health centres to identify early signs;
- Offering training programmes to help parents monitor and report developmental concerns;
- Ensuring healthcare and early years professionals can recognise subtle early signs and make timely referrals;
- Supporting ongoing research to improve detection and intervention strategies.
These key recommendations demonstrate how the study of SIBs-A not only enhances early identification efforts but also informs best practices in clinical and community settings. For instance, one study (Green, 2019) highlights the central role of the family in early developmental support. Her parent-mediated intervention, Video Interaction to Promote Positive Parenting, was associated with reductions in autism-related traits after a 36-month follow-up, based on both AOSI and ADOS assessments.
Given the strong genetic link, SIBs-A should receive regular screening. Evidence of developmental delays in this population supports the use of early enrichment programmes, where parents learn to integrate supportive strategies into daily routines (Landa et al., 2012). Whether in structured settings or more naturalistic interactions, such early engagement offers valuable insights into emerging social communication patterns (Gangi et al., 2021). These studies demonstrate that SIBs-A research is not only scientifically valuable but also highly beneficial for families seeking guidance, reassurance, and timely support.
The Limitations and Ethical Considerations of Studying SIBs-A
While the benefits of studying SIBs-A are clear, some studies have drawn attention to the methodological and ethical challenges associated with SIBs-A research. One concern stems from the clinical heterogeneity of autism (Newschaffer et al., 2012), and the fact that a singular biological marker for the condition has yet to be identified (Manzini et al., 2021). Furthermore, infants who are later diagnosed with autism often show no obvious behavioural differences at six months of age, with typical vocalisation and attention to faces (Ozonoff et al., 2010). Declines in social gaze and eye contact tend to become apparent between 12 and 36 months (Gangi et al., 2021). Though some early signs are observable, the first year of life presents limited behavioural markers (Jones et al., 2014), and reliable diagnosis is typically feasible only from age two (Lord et al., 2020).
Gangi et al. (2021) identified four developmental trajectories in autism: early-onset delays, regression after typical development, a mixed profile, and a plateau in development. While not all infants display early indicators, a substantial proportion—particularly those in the early-onset and plateau groups—do show signs within the first year. Even if early diagnosis is currently accurate in only 10–36% of cases, this still represents a meaningful opportunity for early monitoring and support.
Outside of well-resourced, multidisciplinary settings, practical concerns persist—namely, who is qualified to detect subtle differences in infant behaviour, and how should ‘normal’ variation be interpreted? These are valid questions, and while early signs can be difficult to define, many studies suggest that identifying at-risk children enables families to access beneficial interventions sooner rather than later.
Despite the complexities, ethical considerations should not deter researchers from pursuing early identification. Instead, they highlight the need for sensitivity, transparency, and support. Labelling infants as “at-risk” (Landa et al., 2012) based on genetic predisposition should be done carefully, and intervention must be based on a clear understanding of potential benefits (Manzini et al., 2021). Informed consent, privacy safeguards, and psychosocial support are essential. When approached responsibly, SIBs-A research not only advances scientific knowledge but also improves early intervention pathways for families navigating the uncertainty of autism.
Conclusion
Studying the infant siblings of autistic children presents a complex but highly valuable opportunity to deepen our understanding of autism’s developmental onset. While methodological limitations—such as the variability in early signs and limited diagnostic reliability before age two—must be acknowledged, these do not eclipse the considerable advantages this research approach offers. In many cases, families already familiar with autism are capable of recognising emerging traits in their younger children and are not primarily concerned with premature labelling but rather with gaining access to timely and meaningful intervention.
The evidence discussed throughout this essay demonstrates that SIBs-A studies help illuminate early differences in areas such as language, motor development, and social attention. Importantly, this research allows for close observation and monitoring, which can lead to earlier, better-targeted support strategies. The potential to reduce the distress caused by prolonged diagnostic uncertainty—and to bridge the gap between early parental concerns and formal recognition—is a key strength of this approach. Moreover, training and resources developed through SIBs-A studies can benefit broader clinical practice by equipping professionals and families with sharper tools for early observation.
Although ethical concerns—such as the potential anxiety provoked by risk labelling—are significant, they can be effectively managed through transparent communication, thoughtful consent processes, and robust emotional support. When these conditions are in place, the benefits of SIBs-A studies far outweigh their limitations. Such research not only advances clinical and scientific understanding but also empowers families with earlier insights, offering a path to improved outcomes for children whose developmental differences might otherwise go unrecognised until much later. In this context, SIBs-A research should be seen not as a risk, but as a valuable opportunity that, when conducted responsibly, serves both science and society. Finally, the continued provision of research funding and strong ethical oversight is essential to ensuring that SIBs-A studies remain both effective and ethically sound.
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