Grace Franckel, Jacalyn Guy and Joni Holmes
In CALM, we look beyond diagnostic labels and instead use a transdiagnostic approach to understand the cognitive and neural features that define children’s strengths and difficulties. Exploring the relationships between these different features has so far revealed that behavioural problems, patterns of cognitive difficulties and neural profiles do not align with specific diagnoses. Our findings support the importance of child-centred, rather than diagnosis-centred, approaches to assessment and intervention.
The CALM Approach
Our thinking around neurodevelopmental disorders is undergoing a period of rapid change. The traditional approach, endorsed by classification systems such as the Diagnostic Statistical Manual, defines neurodevelopmental disorders such as autism and attention-deficit hyperactivity disorder (ADHD) as distinct categories. The majority of research studies reflect this categorical approach by commonly adopting case-control designs, in which participants with one diagnostic label are compared to a group with a different diagnosis or a ‘control sample’. The assumptions of such designs are that individuals with a particular diagnostic label are more similar than different, and that there are few commonalities between children with different diagnoses. Children with milder needs that do not reach the threshold for a diagnosis, and those with more complex and co-occurring needs, are often excluded from these studies.
The Centre for Attention, Learning and Memory (CALM) aimed to do things differently. Rather than recruiting participants based on strict inclusion criteria that reflected either diagnostic status, or severity based on cut-off scores on a measure of learning or mental health, we invited education and health professionals to refer children to the study who were struggling in the areas of attention, learning or memory. In total, we recruited 800 children aged 5-18 years. Some children had a diagnosis, others had multiple diagnoses, but most had none at all. Our unique sampling procedure enabled us to adopt what is called a transdiagnostic approach. That is, we could look beyond diagnostic labels, and instead consider the cognitive and neural features that defined children’s strengths and difficulties, and explore the relationships between these different features.
All children completed assessments of cognition and learning, then were invited to provide an optional saliva sample for genetic analysis, and invited for an optional MRI brain scan. Their parents/carers completed questionnaires about the children’s behaviour, mental health and communication skills. A comparison sample of 200 children attending the same schools as those referred to the main study completed the same assessments. We are now following up all 1000 children approximately 3-5 years after their initial assessment.
What have we learned from CALM?
1. Behaviour and communication skills are not related to diagnoses
Specific behaviours such as distractibility, fidgeting, and poor concentration are often seen in children who struggle in the classroom, and form part of the diagnostic criteria for neurodevelopmental disorders such as ADHD. Such behaviours may arise from deficits in executive functions (EFs) – a collection of cognitive processes that help to regulate thoughts and behaviour. Deficits in EFs are usually compared between children with different disorders in an attempt to characterise particular features of a specific disorder. However, research has shown that similar profiles of EF deficits can occur across children with different disorders and in children with learning-problems who do not have a diagnosis (e.g. Holmes et al., 2014).
We were able to group together children in the CALM study with similar EF profiles based on parent-reports of EF-associated behavioural difficulties (Bathelt et al., 2018). The children fell into one of three groups: (1) elevated inattention and hyperactivity/impulsivity, and poor EF; (2) learning problems; or (3) aggressive behaviour and problems with peer relationships. A child’s diagnosis did not predict which of the three groups they belonged to with any great accuracy, and children with different diagnoses, or with no diagnosis, showed similar profiles of behavioural symptoms. This suggests patterns of EF deficits do not correspond to diagnostic status.
In a later study, we explored how the symptoms of communication skills and EF problems commonly linked to neurodevelopmental disorders were associated with each other (Mareva & Holmes, 2019). We identified four sets of symptoms. One related to social communication problems and difficulties with peer relationships, another linked to emotional and behavioural difficulties, a third linked to EFs, such as working memory and inattention, and a fourth linked to learning and formal language use. These sets of symptoms did not correspond to any one set of diagnostic features for a specific disorder
Taken together, these two studies imply that children’s behavioural problems do not align with their diagnoses, and that considering children’s individual EFs and co-occurring symptoms could be more informative when thinking about the support they might need.
2. Diagnoses do not map on to underlying cognitive and neural characteristics
Using machine learning, we grouped together children with similar cognitive profiles in the CALM sample, and investigated how children in each group differed in terms of their learning (Astle et al., 2019). We identified four groups of children: (a) those with broad cognitive difficulties, who had the most severe and broadest set of difficulties in learning; (b) those with age typical cognitive abilities who had the most age-appropriate learning profiles; (c) children with spatial and working memory problems; and (d) children with phonological difficulties. Despite their contrasting cognitive profiles, the learning profiles of the latter two groups did not differ: both were below age expected levels on all learning measures. Children with the same diagnosis appeared across the groups (e.g. children with ADHD were found in all four groups). These data suggest that diagnoses do not map on to underlying cognitive profiles, and that there may be different cognitive routes to the same learning profiles. We have also identified different neural profiles among the children in CALM, and investigated how these profiles related to cognitive function (Siugzdaite et al. 2020). Crucially, we found the same neural profile could be associated with different cognitive impairments across different children, and that a child’s neural profile could not predict the presence of a particular diagnosis.
These studies suggest that diagnoses do not map on to underlying cognitive or neural characteristics, and show children with and without diagnosed developmental disorders of learning can experience the same cognitive difficulties as one another and have similar neural profiles.
The CALM findings add weight to the argument that neurodevelopmental disorders are highly comorbid, heterogeneous, explained by multiple causes, and not captured by a cardinal set of symptoms. This stands in contrast to theories that specify a particular cognitive or behavioural impairment as being the route to a specific diagnosis. The data-driven approaches used in CALM indicate that we should be moving towards child-centred and not diagnosis-centred approaches to both assessment and intervention if we are to find the best way to support children’s needs.
Astle, D. E., Bathelt, J., Team, C., & Holmes, J. (2019). Remapping the cognitive and neural profiles of children who struggle at school. Developmental Science, 22(1), e12747. https://doi.org/10.1111/desc.12747
Bathelt, J., Holmes, J., Astle, D. E., Gathercole, S., Manly, T., & Kievit, R. (2018). Data-Driven Subtyping of Executive Function–Related Behavioral Problems in Children. Journal of the American Academy of Child & Adolescent Psychiatry, 57(4), 252–262. https://doi.org/10.1016/j.jaac.2018.01.014
Holmes, J., Hilton, K. A., Place, M., Alloway, T. P., Elliott, J. G., & Gathercole, S. E. (2014). Children with low working memory and children with ADHD: same or different? Frontiers in human neuroscience, 8, 976.
Mareva, S., & Holmes, J. (2019). Transdiagnostic associations across communication, cognitive, and behavioural problems in a developmentally at-risk population: a network approach. BMC pediatrics, 19(1), 452.
MRC Cognition and Brain Sciences Unit
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