Lancaster, H. S., & Camarata, S. (2019). Reconceptualizing developmental language disorder as a spectrum disorder: issues and evidence. International journal of language & communication disorders, 54(1), 79–94. https://doi.org/10.1111/1460-6984.12433
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What was the aim?
Developmental language disorder (DLD) is very complex, and it can present itself very differently across individuals. There are mixed opinions about how to interpret this variability which makes diagnosis and treatment difficult. The authors aimed to test three models for characterizing the variability in presentation in DLD. Namely, these models were: the subtype model; the individual differences model; and the continuum/spectrum approach (see below for clarification). More specifically they aimed to highlight that (1) children with DLD are a separate group of language learners, and (2) there is a need to examine individual differences.
‘Subtype model’ - suggests that the variability within DLD (i.e. the different symptoms) results from there being different ‘subtypes’ of the disorder. One common medical example would be Diabetes Type I and Diabetes Type II.
‘Individual differences model’ - suggests that the variability happens at random, as a result of the unique characteristics of each individual (i.e. characteristics outside of their DLD).
‘Continuum/spectrum approach’ - suggests that there are shared common features across all individuals with DLD, but each individual presents with different characteristics (or symptoms) depending on where they sit on a continuous spectrum. The spectrum-nature of it (i.e. being continuous, rather than distinct), means that these individuals cannot be separated into distinct subgroups easily.
What was found?
Results actively reject the subtype model of DLD
There is partial support the individual differences model
There is full support of the continuum/spectrum model
What does it mean?
Addressing past mixed research, these results indicate that there are no meaningful subtypes of DLD. Thus, the subtype model seems unlikely to explain variation in presentation of DLD. The partial support for the individual differences model as well as the mixed research suggests that this solution still remains an open question. Lastly, the research found full support for the continuum/spectrum model which suggests that there is evidence of a spectrum disorder of language abilities. This means that children with DLD do not vary by specific symptoms, but within a cohesive distinct diagnostic group. These results will benefit the assessment and development of treatment for people with DLD. Treatments focused on the individual and demand for the development of new assessment procedures focused on core elements and functional capacity will eventually be developed.
Where can I read this paper?
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