Editorial: capturing developmental trajectories of change in persons with intellectual and developmental disability

Cognitive and adaptive functioning in congenital and childhood forms of myotonic dystrophy type 1: a longitudinal study

AIM

To conduct a longitudinal follow-up of the development of global cognitive abilities and adaptive skills in individuals with congenital and childhood forms of myotonic dystrophy type 1 (DM1).

METHOD

Fifty-one participants (29 males, 22 females, mean age 19y 5mo, SD 4y 11mo, range 10y 10mo-28y 11mo) were divided into severe congenital (n=16), mild congenital (n=17), and childhood DM1 (n=18) subgroups. The average time between the first and second assessments was 7 years 8 months. Adaptive skills were evaluated using the Vineland Adaptive Behavior Scales and global cognitive functioning using Wechsler scales.

RESULTS

There was no statistically significant decline in cognitive abilities and adaptive behaviour. A tendency of decline regarding the level of intellectual disability was found in the congenital DM1 groups but not in the childhood group. In the congenital DM1 groups, the gap in relation to typically developing peers in cognitive and adaptive functioning increased. Predictors of change over time in adaptive skills were age and current level of intellectual disability: individuals with severe intellectual disability and younger individuals deteriorated the most. However, when raw scores were compared, no actual regression in adaptive functioning was found.

INTERPRETATION

The participants had not lost any important adaptive skills. Greater cognitive and adaptive development was found in the childhood group than in the congenital groups.

WHAT THIS PAPER ADDS

There is no absolute decline in cognitive and adaptive abilities in individuals with congenital and childhood myotonic dystrophy type 1. Pace of development is slow in comparison with normative data. The childhood group tended to show greater cognitive and adaptive development than the congenital groups.

Empirically Identified Subgroups of Children Served in Part C Early Intervention Programs

OBJECTIVE

Early intervention (EI) programs under Part C of the Individuals with Disabilities Education Act serve a developmentally heterogeneous population of infants and toddlers with or at risk of developmental delays or disabilities. The aim of this study was to identify empirically distinct subgroups of children in EI so as to inform early prognosis and service planning.

METHODS

We applied mixture modeling to developmental assessment data from 1513 children who enrolled in a large, urban EI program between 2009 and 2013. The observed variables were children's EI-entry developmental quotients (DQs) in 5 domains (communication, cognitive, motor, adaptive, and personal-social) as assessed by the Battelle Developmental Inventory, Second Edition.

RESULTS

A 4-class model showed the best fit to the data, revealing subgroups with distinct developmental profiles. Children in the first subgroup showed a severe delay in communication with less severe delays in the other domains. Children in the second subgroup likewise showed a severe delay in communication, but with comparably severe delays in the cognitive and motor domains. Profiles for the third and fourth subgroups showed the same overall patterns as those for the first and second subgroups, respectively, but to a less severe degree. Developmental trajectories differed by subgroup.

CONCLUSION

Consideration of subgroups based on children's developmental assessment scores provides insight into underlying commonalities among children with different presenting diagnoses on entry into EI. The subgroups also have clinical relevance in terms of both practitioners' and parents' understanding of children's likely service needs and developmental trajectories.

Developmental trajectories of structural and pragmatic language skills in school-aged children with Williams syndrome

BACKGROUND

This study aimed to compare developmental courses of structural and pragmatic language skills in school-aged children with Williams syndrome (WS) and children with idiopathic intellectual disability (IID). Comparison of these language trajectories could highlight syndrome-specific developmental features.

METHOD

Twelve monolingual Dutch-speaking children with WS aged 5.10 to 13.3 years were assessed by means of standardised structural language tests measuring receptive and expressive vocabulary and sentence comprehension and production. Pragmatic language was evaluated by means of an expressive referential communication task and a retelling test. All of these language abilities were re-evaluated with the same measures after a period of 18 to 24 months. Performance was compared to 12 children with IID pairwise matched for chronological age (CA) and non-verbal fluid reasoning (Gf) at Time 1. Non-verbal mental age (NVMA) was taken into account when delineating developmental trajectories.

RESULTS

Children with WS outperformed children with IID on expressive vocabulary development. In contrast, sentence comprehension was significantly poorer than in children with IID at the second time point. Increased variability and rather poor performance on pragmatic language tasks were demonstrated in the WS group. Irrelevant and off-topic extraneous information transfer continued to be a syndrome-specific characteristic of children with WS.

CONCLUSION

The data provide new insights into diverging developmental trajectories across language domains. Expressive structural language skills tend to progress more rapidly than receptive language skills in children with WS causing more distinctive language profiles over time. Some children with WS seem to benefit from the growth in expressive structural language abilities to enhance their expressive pragmatic language skills, while in some others these abilities remain challenging. This study highlights the need for continued follow-up of language challenges in WS and for a dynamic and individualised interventional approach.

Cardiac autonomic regulation in autism and Fragile X syndrome: a review

Despite the significance of efforts to understand the biological basis of autism, progress in this area has been hindered, in part, by the considerable heterogeneity in the disorder. Fragile X syndrome (FXS), a monogenic condition associated with high risk for autism, may pave the way for the dissection of biological heterogeneity within idiopathic autism. This article adopts a cross-syndrome biomarker approach to evaluate potentially overlapping profiles of cardiac arousal dysregulation (and broader autonomic dysfunction) in autism and FXS. Approaches such as this, aimed at delineating shared mechanisms across genetic syndromes, hold great potential for improving diagnostic precision, promoting earlier identification, and uncovering key systems that can be targeted in pharmaceutical/behavioral interventions. Biomarker approaches may be vital to deconstructing complex psychiatric disorders and are currently promoted as such by major research initiatives such as the NIMH Research Domain Criteria (RDoC). Evidence reviewed here supports physiological dysregulation in a subset of individuals with autism, as evidenced by patterns of hyperarousal and dampened parasympathetic vagal tone that overlap with the well-documented physiological profile of FXS. Moreover, there is growing support for a link between aberrant cardiac activity and core deficits associated with autism, such as communication and social impairment. The delineation of physiological mechanisms common to autism and FXS could lend insight into relationships between genetic etiology and behavioral endstates, highlighting FMR1 as a potential candidate gene. Research gaps and potential pitfalls are discussed to inform timely, well-controlled biomarker research that will ultimately promote better diagnosis and treatment of autism and associated conditions.