Autism Spectrum Disorder in Down Syndrome: Experiences from Caregivers

Autism spectrum disorder (ASD) is a common co-occurring condition in individuals with Down syndrome (DS). Estimates of prevalence range broadly from 5 to 39% (Capone et al, 2005; DiGuiseppi et al, 2010; Hepburn et al, 2008; Lowenthal et al, 2007; Moss et al, 2013; Richards et al, 2015; Starr et al., 2005), depending on the assessment procedures and diagnostic criteria used. This suggests that ASD is much more prevalent in children with DS than in the general population, where the estimated prevalence of ASD is 1.85% (Maenner et al., 2020).

Despite this well-described co-occurrence, ASD is often diagnosed at a later age in patients with DS, if they are diagnosed at all (Howlin et al., 2008; Rasmussen et al, 2001). Thus, children with a dual diagnosis of Down syndrome-autism spectrum disorder (DS-ASD) may miss the window for intensive early intervention, which has been shown to lead to better developmental outcomes in individuals with idiopathic ASD (Greenspan, 1994; Lovaas, 1987; Webb et al, 2014). Though some studies have shown that developmental regression associated with ASD occurs later in children with DS compared to children without DS (Castillo et al, 2008; Warner et al, 2014), other factors, such as decreased awareness of DS-ASD, differences in ASD symptomatology, and diagnostic overshadowing, can lead to a later diagnosis. Older literature described people with DS as friendly and affectionate (Gibbs & Thorpe, 1983), and suggested that ASD rarely co-occurs in individuals with DS (Gillberg et al, 1986; Rutter & Hersov, 1985; Rutter & Schopler, 1988). A recent study comparing children with DS-ASD to ASD alone demonstrated that though these two groups have similar profiles of communication and repetitive behaviors, children with DS-ASD have milder social difficulties, more imitative play, and less impairments in eye gaze and social smiling (Warner et al., 2017). Further, recognizing ASD in children with DS is a challenge due to overlapping symptomatology between intellectual disability and ASD, as both can be associated with deficits in communication, play, and behavioral difficulties. ASD-like symptoms are also more frequently seen in individuals with DS without a co-morbid ASD diagnosis than in the neurotypical population (Channell et al, 2015), which may lead providers to believe that their patient’s neurocognitive profile is solely attributable to intellectual disability, rather than suspecting an additional diagnosis of ASD (Howlin et al, 2008; Reiss et al., 1982).

Parent perspectives provide valuable input in developing tailored care models for different patient populations (Findlen et al., 2019). Parent observations, including developmental and behavioral concerns, have been shown to be predictive of a subsequent diagnosis of ASD (Sacrey et al., 2015). While studies have inquired about the experience of caregivers of children with DS or ASD (Ashworth et al., 2019; Dabrowska & Pisula, 2010; King et al, 2012; Siklos & Kerns, 2006), little is known about the perspective of caregivers of individuals with DS-ASD. The goal of this study was to learn about caregivers’ perspectives, observations, and lived experience with their child with DS-ASD, and to document the journey from early concerns to diagnosis and intervention. Clinical experience informed the hypothesis that caregivers encountered barriers to obtaining an ASD diagnosis, and that their parenting experience was different from that of caregivers of individuals with DS alone.

This study is the first to look at perspectives of caregivers with a child with DS-ASD. The use of qualitative coding and theme analysis enabled a detailed and nuanced view of family perspectives. Children with DS-ASD are a relatively understudied patient population, and this study offers valuable insight into their families’ lives.

Most survey respondents noticed that their child was different from others with DS in early childhood, with a mean age of first concern at 3.87 years old. In comparison, multiple studies of children with idiopathic ASD have reported initial parental concern before the age of 2 (Baghdadli et al, 2003; Chamak et al, 2011; Chawarska et al, 2007; De Giacomo & Fombonne, 1998; Goin-Kochel et al., 2006; Howlin & Asgharian, 1999; Zuckerman et al., 2015). This study found an average 4.65-year delay between first noticing symptoms and obtaining a diagnosis. This “age gap” is greater than the one reported in a United States- based survey of caregivers of individuals with idiopathic ASD, which found that the mean delay between the first conversation with a provider and diagnosis of ASD was 2.70 years (Zuckerman et al, 2015). Children with DS-ASD in our study were diagnosed at an average age of 8.52 years, which is several years older than the reported average age at diagnosis of 5–6 years in idiopathic ASD (Howlin & Moore, 1997; Mandell et al, 2010; Siklos & Kerns, 2007). Notably, the “age gap” was larger for individuals who were older at the time the survey was completed, suggesting that there has been some improvement in the recognition and diagnosis of ASD in children with DS over the past three decades. It should be noted that this finding could have been confounded by the wide age range of individuals with DS-ASD at the time that the survey was completed.

The identification and diagnosis of ASD in individuals with DS can be complicated by multiple factors. The core symptoms of ASD (social-communicative impairments and repetitive behaviors and interests) may be less pronounced in DS-ASD than in ASD alone (Godfrey et al, 2019). The overlap of symptoms between the intellectual disability and ASD can cause a diagnostic dilemma for providers (Howlin et al, 2008; Reiss et al, 1982); for example, many children with DS and more severe intellectual disability have stereotyped behaviors (Channell et al, 2015; Kraijer & de Bildt, 2005). ASD-like symptoms, as rated on the Social Responsiveness Scale, are more prevalent in individuals with DS without a co-morbid ASD diagnosis than in the neurotypical population (Channell et al, 2015). Hearing loss, hypotonia, and visual impairment, all of which occur with high incidence in individuals with DS, may also affect language and social development (DiGuiseppi et al, 2010; Rasmussen, 2001). While challenging even for an astute provider to know when ASD-like symptoms indicate an ASD diagnosis, the presence of multiple signs and symptoms, as well as a concern that a child is “different” from other children with DS, should prompt further evaluation by a specialist, rather than being dismissed as attributable to DS or intellectual disability alone. Of note, the characteristics that were identified as differentiating children with DS-ASD from other children with DS only, as articulated by survey respondents, are consistent with scoring algorithm items on the Autism Diagnostic Observation Schedule (ADOS)—the “gold standard” diagnostic tool for diagnosing ASD in the general community (Lord et al, 2000). Individuals with DS-ASD have been shown to have similar ADOS profiles as children with idiopathic ASD (Oxelgren et al., 2019).

Parental reports in the survey correlated well with published findings on DS-ASD, further supporting the notion that parental concerns should not be ignored or dismissed. The most commonly reported symptom was stereotypic behavior (n = 24, 53%), consistent with previously published findings of higher rates of stereotypy on the Aberrant Behavior Checklist in children with DS-ASD compared to children with DS only (Capone et al, 2005); the literature has shown that while many children with DS display stereotypic behavior (Howlin & Moore, 1997), those with DS-ASD engage in more persistent, complex and bizarre stereotypy (Carter et al, 2007). Caregivers commonly reported mood and behavior concerns, which supports previous findings of higher rates of behavior difficulties, hyperactivity, and inappropriate speech in individuals with DS-ASD compared to DS only (Capone et al, 2005; Carter et al, 2007; Molloy et al, 2009). Of note, a recent study found that specific types of maladaptive behaviors, such as self-harm and withdrawal, were associated with higher risk of DS-ASD (Channell et al, 2019). In our survey, parents also frequently reported significant communication difficulties, consistent with findings that individuals with DS-ASD have poorer receptive and expressive language abilities and more inappropriate speech than those with DS alone (Magyar et al., 2012; Molloy et al, 2009).

Early diagnosis is a major determinant of outcomes in patients with ASD, since intensive interventions early in life may lead to better outcomes (Greenspan, 1994; Kraijer & de Bildt, 2005; Webb et al, 2014). A common theme among survey respondents was that their concerns were initially dismissed, contributing to the delay in ASD diagnosis. For many of the participants, the journey to a dual diagnosis involved interactions with multiple providers, educators, and therapists before finding one who was able to recognize the signs of ASD and evaluate them; this highlights a lack of awareness of DS-ASD, and suggests the need for education, especially for primary care providers and educators, who are often the first to hear parental concerns.

Having a child with dual diagnosis has a huge impact on a family, both positive and negative. Thirty eight percent of participants reported feelings of isolation, which parents attributed to two major categories—the inability to leave the home or attend family gatherings due to the child’s behavior or sensory issues and being misunderstood as “bad parents” in public due to their child’s symptoms and behaviors. This is consistent with findings that the “DS advantage” – the notion that parents of individuals with DS experience less stress and greater parenting satisfaction when compared with caregivers of children with other developmental disabilities (Hodapp et al., 2001) – does not hold true when controlling for the child’s adaptive behavior (Corrice & Glidden, 2009). The survey results highlight the value of adequate respite services for children with DS-ASD. Parents relied on building a community with the families of other dually diagnosed children, underscoring the importance of connecting families to online and in-person support groups. Studies have found that social support is a very important factor related to the coping of families of children with ASD and helps reduce their stress levels (Luther et al., 2005).

This study provides insight on how we can enhance care for children with DS-ASD through improved understanding of families’ experiences. However, this study had several limitations. Our sample size was small, with only 47 survey meeting inclusion criteria. The survey solicited very limited demographic data, which affects the generalizability of its findings. Surveys were included based on parent report that their child had been diagnosed with DS-ASD, with no independent verification process; given that diagnosing ASD in genetic syndromes is more challenging (Hepburn & Moody, 2011), future research studies should include additional characterization measures of ASD symptomatology, to increase confidence that findings truly describe the DS-ASD population. We did not have a comparative group of families of children with DS alone or ASD alone; future research should include these comparison groups, who may experience similar challenges with school programming and access to services. While the open-ended format of the survey questions allowed respondents to freely express themselves, it also introduced the potential for bias in the process of grouping responses into categories. Given our reliance on survey data, there may be recall bias in the reporting of initial concerns around symptoms, since parents are more familiar with the diagnostic criteria for ASD after their child has been diagnosed. There may also be negativity bias with patients remembering challenges with accessing diagnostic and intervention services, which may have occurred years prior to survey completion.

Participants in our study may not be representative of parents in the general population, as they needed to read and write in English, be members of the DS-ASD connection (the online support group where participants were recruited) and have access to the internet to complete the survey. The results are subject to significant selection bias, as all respondents were members of a support group who may have sought out an online community to cope with more challenging parenting experiences. In studies focusing on idiopathic ASD, being a non-English speaker was associated with delays in ASD diagnosis (Fountain, King, Bearman, 2011; Valicenti-McDermott et al, 2012), suggesting the possibility that children with DS-ASD who come from non-English speaking families, minority groups, or lower socio-economic statuses may be experiencing even greater delays in diagnosis. We hope that this study will prompt further inquiry into the experiences of caregivers of individuals with DS-ASD, including those whose primary language is not English, with more detailed categorization of participants’ racial/ethnic background, education level, and socio-economic status.

This study corroborates previous findings that diagnosis of ASD in children with DS is significantly delayed (Howlin et al, 2008; Rasmussen et al, 2001). It also substantiates prior research showing that children dually diagnosed with DS-ASD experience greater challenges with behavior, adaptive functioning, and communication than children with DS alone (Magyar et al, 2012; Molloy et al, 2009). This study underscores the importance of validating parental concerns and promptly connecting patients with signs of ASD with appropriate evaluations and services and emphasizes the need for educating primary care providers and educators on the presentation and needs of individuals with DS-ASD. This study also highlights the need for ongoing research on how children with DS-ASD differ from those with DS alone, and the importance of supporting caregivers by connecting them with meaningful respite and supportive services at home and in the community.