Developmental Language Disorder (DLD) in relation to DSM-5

The tl;dr (too long, didn't read) message in this post is that for all intents and purposes, Developmental Language Disorder (DLD), as defined in the CATALISE project, can be regarded as equivalent to DSM-5 Language Disorder (American Psychiatric Association, 2013). This is a question of interest to people working in systems that require a DSM-5 diagnosis for access to services or insurance payments.

Diagnostic flowchart for CATALISE, based on Figure 1 from Bishop et al (2017).

https://doi.org/10.6084/m9.figshare.11917899.v1

Figure 1 shows how DLD is defined in the CATALISE project (Bishop et al, 2017). In this framework, DLD is a subset of the broader term 'Language Disorder', with the 'Developmental' prefix used to indicate that the language problems are not associated with a known biomedical condition. The list of biomedical conditions includes brain injury, acquired epileptic aphasia in childhood, certain neurodegenerative conditions, cerebral palsy, oral language limitations associated with sensori-neural hearing loss, autism, intellectual disability and genetic conditions such as Down syndrome.

In DSM-5, 'Language Disorder' is used with a meaning that closely corresponds to DLD. DSM-5 Diagnostic criteria for Language Disorder (category 315.32; F80.2) are as follows:

A. Persistent difficulties in the acquisition and use of language across modalities (I.e. spoken, written, sign language, or other) due to deficits in comprehension of production that include the following: 

• Reduced vocabulary (word knowledge and use) 
• Limited sentence structure (ability to put word and word endings together to form sentences based on the rules of grammar and morphology 
• Impairments in discourse (ability to use vocabulary and connect sentences to explain or describe a topic or series of events or have a conversation) 

B. Language abilities are substantially and quantifiably below those expected for age, resulting in functional limitations in effective communication, social participation, academic achievement, or occupational performance, individually or in any combination 
C. Onset of symptoms is in the early developmental period 
D. The difficulties are not attributable to hearing or other sensory impairment, motor dysfunction, or another medical or neurological condition, and are not better explained by intellectual disability (intellectual developmental disorder) or global developmental delay. 

The relationship between the CATALISE terminology and DSM-5 are shown in Figure 2. In both CATALISE DLD and DSM-5 Language Disorder, cognitive referencing is not used (i.e. there is no IQ cutoff for inclusion in the category), the language problems are seen in early childhood and are persistent and lead to functional impairment, and children with associated biomedical conditions are excluded. 

Figure 2: Set diagram showing relationship between CATALISE and DSM-5 terminology

The CATALISE criteria are more explicit than DSM-5 in relation to bilingual/multilingual children, making it clear that one would not diagnose DLD unless the child showed poor language competence in their best language, but a similar idea is conveyed in the "Differential diagnosis" section of DSM-5, where it is noted that "Language disorder needs to be distinguished from normal developmental variations... Regional, social, or cultural/ethnic variations of language must be considered when an individual is being assessed for language impairment." Unfortunately, a recent account of DLD by a member of the CATALISE panel stated that bilingual/multilingual children were excluded from the DLD category (Rice, 2020). It is unclear how this misunderstanding arose, but it is clearly discrepant with Figure 1.

One might ask why the CATALISE panel decided against alignment with the DSM-5 terminology, given that there is such overlap between CATALISE DLD and DSM-5 Language Disorder. The answer is that "Language Disorder" as defined in DSM-5 is a problematic label because on the one hand it refers to a specific DSM-5 category 315.32 (F80.2), but on the other hand it is widely used to refer to symptom-level problems in many conditions. "Language disorder" is a hopeless term to use in a literature search because it will turn up a far broader range of conditions than those defined by the diagnostic criteria above, including many types of acquired language disorder associated with both developmental and adult-onset conditions.

This broader meaning of the term gives ample scope for confusion. Indeed, even within the DSM-5 manual, ambiguity is apparent. Under "Differential diagnosis" mention is made of Neurological disorders, with the statement "Language disorder can be acquired in association with neurological disorders, including epilepsy (e.g. acquired aphasia or Landau-Kleffner syndrome)". A literal reading of this would mean that, contrary to Diagnostic criteria point D, children with acquired aphasia or Landau-Kleffner syndrome can be regarded as having Language Disorder. I don't think that is what the authors intended: rather they imply that one should differentiate acquired language disorder associated with neurological conditions from "Language Disorder" that corresponds to DSM-5 category 315.32 (F80.2).

In short, in proposing the DLD label, the CATALISE panel were capturing a grouping that is conceptually the same as DSM-5 Language Disorder. We felt, however, that 'Language Disorder" was a problematic label that would generate confusion, and so we used the more traditional term "Developmental Language Disorder" specifically to identify a category of language disorder without associated biomedical conditions.

References
American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington, VA: American Psychiatric Publishing.
Bishop, D. V. M., Snowling, M. J., Thompson, P. A., Greenhalgh, T., & CATALISE Consortium. (2017). Phase 2 of CATALISE: a multinational and multidisciplinary Delphi consensus study of problems with language development: Terminology. Journal of Child Psychology and Psychiatry, 58(10), 1068-1080. doi:10.1111/jcpp.12721
Rice, M. (2020). Clinical lessons from studies of children with Specific Language Impairment. Perspectives of the ASHA Special Interest Groups, 5(1), 12-29. doi:https://doi.org/10.1044/2019_PERSP-19-00011

Changing terminology for children's language disorders: reflections on special issue of Perspectives of the ASHA Special Interest Groups

In 2016-7, I joined with expert colleagues to try to tackle the thorny issue of terminology for children who had difficulties speaking or understanding in their native language. This was incredibly challenging: we had a panel of 57 experts, moderated by Maggie Snowling and me, engage in a Delphi process, whereby we iteratively rated and commented on statements to do with identification and diagnosis to converge on a set of recommendations (Bishop et al., 2016; 2017). There was substantial disagreement between experts, who came from a range of disciplines and nationalities, but the one thing we agreed upon was that the current situation – of a plethora of different terms being used with various meanings – was doing a grave disservice to families and their children affected by language problems. There was a lack of recognition of language problems among professionals and the general public, as well as a paucity of research relative to other conditions of similar severity and prevalence. Eventually we converged on a recommendation that the term 'Developmental Language Disorder' (DLD) should be used to describe children with persistent problems with language expression or reception that had no obvious cause, and that impacted on everyday life.

Publication of the 2017 recommendations had considerably greater impact than I had anticipated, thanks to the generally enthusiastic take-up of the new terminology, which has been adopted by professional organisations in the UK, Ireland and Australia. A brief summary of the salient points was written by Susan Ebbels for the Royal College of Speech and Language Therapists.

Following the publication of the CATALISE papers, big changes have happened just in a couple of years:

• The terminology has stimulated development of grassroots advocacy, with campaigns to promote awareness of DLD adopting ingenious and innovative methods to publicise events. See e.g. here.
• The DLD label has raised awareness that this is a life-long condition*. Adults with DLD have started to talk about their experiences on social media (e.g. here). 
• Figures on terminology from Web of Science show that DLD is starting to overtake the term 'Specific Language Impairment' in published papers.
   



Figure 1: N publications with full term 'Specific Language Impairment' or 'Developmental Language Disorder' in the Topic field; data from Web of Science


Nevertheless, despite these positive developments, not everyone has been convinced that adoption of DLD is a good thing. This is not surprising: a couple of years ago, I reflected on some of the reasons why this particular topic is a terminological minefield (Bishop, 2017). It is difficult to balance the pros and cons of new terminology, especially when one is dealing with a condition that is heterogeneous, changes with age, can co-occur with many other problems, and is of relevance to several professions with very different perspectives, in particular speech-language therapists/pathologists, educators and medics.

Resistance to new terminology appears to be strongest in the USA, with the American Speech-Language-Hearing Association being particularly cautious about replacing the term Specific Language Impairment with DLD. This week they published a set of papers by individuals with different viewpoints on the topic, and reading through this I was reminded of many of the debates we had in the course of our Delphi exercises. The special issue includes a  tutorial overview by Karla McGregor and colleagues (McGregor et al., 2020), who summarise the background to the CATALISE project, and subsequent developments. They are supportive of DLD, not least because of the way the new terminology has boosted the profile of children's language problems and stimulated greater efforts towards advocacy. But we need to take seriously the concerns of those who have doubts.

Two authors in particular, Larry Leonard and Mabel Rice, were concerned that if we adopt DLD as the preferred term, decades of research on SLI would be ignored and ultimately forgotten. Both of them have made major lifetime contributions to the field, and so their concerns are understandable. It is vital that we heed Larry's advice (Leonard, 2020) to ensure that we include the search term SLI as well as DLD when drawing together relevant literature, to ensure valuable work from previous decades is not lost.

A related issue is that, although they overlap, SLI and DLD are not identical. In general, DLD is a more inclusive term, as it does not require that nonverbal IQ is 85 or over (although it does exclude cases of intellectual disability**), and it is compatible with the presence of other neurodevelopmental disorders, especially developmental co-ordination disorder and attention-deficit-hyperactivity disorder. Rice (2020) remains strongly opposed to the use of DLD, mainly because this would entail including children with nonverbal IQs below 85 (who were termed cases of nonspecific language impairment, or NLI, in a big epidemiological study, the Iowa study). Yet this stance is hard to reconcile with her view that nonverbal ability is independent of language. She spends several paragraphs presenting evidence that it is possible to have low nonverbal ability and good language, or high nonverbal ability and poor language, culminating in the statement: 'The common assumption that children with SLI are not very smart is unwarranted, as is the assumption that all children with strong language aptitude are smart.' It is unclear to whom she is referring as making this 'common assumption'. A major reason why the CATALISE group decided to drop 'cognitive referencing' in defining DLD was because the bivariate distribution of nonverbal IQ and language demonstrates rather a weak association – just as she claims - but this makes it clear that any division into those above and below an IQ threshold is arbitrary (see Figure 2). Just to be absolutely clear, in proposing we do away with nonverbal IQ criteria for DLD, the CATALISE consortium were not saying that children with SLI are 'not very smart'. We were saying that they key thing is what your language is like, and that nonverbal ability is largely irrelevant when making that judgement.

Figure 2: Language composite measure plotted against non‐verbal IQ for 603 eight‐year‐old children in the Iowa study. Figure from Reilly et al (2014). Blue points correspond to SLI, and green points to NLI. NB Axes resized to address criticism by Rice (2020), who found the scaling misleading.

Rice goes on to argue that we need to study children's mastery of specific grammatical markers over time to get a precise measure of children's language in SLI, yet she then goes on to present data showing that children with NLI are also identified by low scores on those markers. Although she claimed a difference in language profiles, this was not evident from the data she presented, and in general, most studies that have looked for qualitative differences between NLI and SLI have failed to find these (see also further evidence from McGregor et al, 2020). Rice maintains that only by sticking with SLI would we find sufficiently clear findings to advance our understanding, and that if we adopt less precise categories, this will lead to muddying of the waters and less replicable results. I regard this as a hypothesis that can be tested, but for which there is currently no good evidence. In fact, it was the failure to find such evidence in my own studies 25 years ago that led me to start to question the construct of SLI (Bishop, 1994).

Larry Leonard makes the sensible suggestion that if we study DLD we should also provide data on which children would meet the more restrictive definition of SLI:  this would, in fact, allow us to test Rice's hypothesis. The best way to do this, and to build on prior studies with SLI would be to make raw data open (see Meyer, 2018), so that results can be analysed to investigate the extent to which findings depend on levels of nonverbal ability, attention, motor skills and so on. There is already precedent for this with the EpiSLI database from the Iowa study (Tomblin, 2010) – this includes data on children who would meet broader DLD criteria as well as more selective SLI cases. This way we could investigate empirically the impact of the choice of criteria, rather than just asserting that one classification approach is better than the other.

I turn next to the other commentary that is predominantly negative about a change of criteria to DLD, that by Murza and Ehren (2020). Their perspective is diametrically opposed to that of Rice. They explain that for speech-language pathologists (SLPs) working in the school system, there is a mismatch between what is taught in their university courses (including diagnosis of SLI) and what they experience in the classroom. There were some parallels here with the views of education experts on the CATALISE panel, some of whom felt the whole debate about labels was irrelevant, and would empathise with the view that: 'No matter the label, students should receive the services they need, and no label should drive services'. But, as Murza and Ehren recognise, labels are needed to demonstrate eligibility for services, and in the USA, this is determined by the Individuals with Disabilities Education Act (IDEA), which has its own set of labels: these don't include either SLI or DLD. I felt a sense of despair coming through from this article, as the authors documented the confusing array of possible terms they could use, each of which had an operational definition, but with that definition varying from one state to another. The impression was that SLPs in US education are up against a massive, unbending bureaucracy that they had to negotiate in order to deliver services to a subset of the children that might benefit from them. In principle, yes, it would be nice to have some consistent terminology that mapped on to the population they were serving, but their conclusion was that they lacked the time, money, energy and focus to embark on a campaign to adopt new labels. This was a considerably more sober and downbeat chapter than that of Rhea Paul, who regarded DLD as potentially compatible with IDEA criteria, and a useful focus for advocacy efforts. 

When discussing relevance of labels for SLP practitioners, another issue concerned insurance eligibility. Karla McGregor reported that she had been told by an insurer: 'If a child just isn't talking or not talking clearly - it is not covered'. The authors also noted a common concern that the term Developmental would be interpreted by insurers, and perhaps others, as implying that the condition would improve of its own accord. But SLPs should not take these kinds of responses lying down: it is grossly inequitable if insurers are willing to pay for a condition such as ADHD or Developmental Co-ordination Disorder, but not for speech-language therapy for a child with DLD. The arguments can and should be made, and it is hoped that the growing awareness of, and advocacy for DLD will empower US SLPs to be more proactive in demanding that children with language disorders are taken seriously and given the support they need.

* Damian Quinn, a man with DLD, has written an autobiography. The timing in relation to CATALISE is probably co-incidental, but this will help with growing awareness that children with DLD do not disappear when they become adults!

** The introductory article for the special issue stated that DLD is used for children 'with or without intellectual disability'. This is wrong. Where the child meets criteria for intellectual disability, the diagnosis would be Language Disorder associated with Intellectual Disability.

P.S. (24 Feb 2020). All the materials from the CATALISE project, including anonymised ratings and comments from the 57 panel members, are available on Open Science Framework.

References

 Bishop, D. V. M. (1994). Is specific language impairment a valid diagnostic category? Genetic and psycholinguistic evidence. Philosophical Transactions of the Royal Society, series B, 346, 105-111. 

Bishop, D. V. M. (2017). Why is it so hard to reach agreement on terminology? The case of developmental language disorder (DLD). International Journal of Language & Communication Disorders, 52(6), 671-680. doi:10.1111/1460-6984.12335

Bishop, D. V. M., Snowling, M. J., Thompson, P. A., Greenhalgh, T., & CATALISE Consortium. (2016). CATALISE: a multinational and multidisciplinary Delphi consensus study. Identifying language impairments in children. . PLOS One, 11(7), e0158753. doi:doi:10.1371/journal.pone.0158753

Bishop, D. V. M., Snowling, M. J., Thompson, P. A., Greenhalgh, T., & CATALISE Consortium. (2017). Phase 2 of CATALISE: a multinational and multidisciplinary Delphi consensus study of problems with language development: Terminology. Journal of Child Psychology and Psychiatry, 58(10), 1068-1080. doi:10.1111/jcpp.12721

Leonard, L. B. (2020). A 200-year history of the study of childhood language disorders of unknown origin: changes in terminology. Perspectives of the ASHA Special Interest Groups, 5(1), 6-11. doi:https://doi.org/10.1044/2019_PERSP-SIG1-2019-0007

McGregor, K. K., Goffman, L., Owen Van Horne, A., Hogan, T. P., & Finestack, L. H. (2020). Developmental Language Disorder: Applications for advocacy, research, and clinical service. Perspectives of the ASHA Special Interest Groups, 5(1), 38-46. doi:https://doi.org/10.1044/2019_PERSP-19-00083

Meyer, M. N. (2018). Practical tips for ethical data sharing. Advances in Methods and Practices in Psychological Science. doi:https://doi.org/10.1177/2515245917747656

Murza, K. A., & Ehren, B. J. (2020). Considering the language disorder label debate from a school speech-language pathology lens. Perspectives of the ASHA Special Interest Groups, 5(1), 47-54. doi:https://doi.org/10.1044/2019_PERSP-19-00077

Paul, R. (2020). Children's language disorders: What's in a name. Perspectives of the ASHA Special Interest Groups, 5(1), 30-37. doi:https://doi.org/10.1044/2019_PERS-SIG1-2019-0012

Rice, M. (2020). Clinical lessons from studies of children with Specific Language Impairment. Perspectives of the ASHA Special Interest Groups, 5(1), 12-29. doi:https://doi.org/10.1044/2019_PERSP-19-00011

Reilly, S., Tomblin, B., Law, J., McKean, C., Mensah, F. K., Morgan, A., . . . Wake, M. (2014). Specific language impairment: a convenient label for whom? International Journal of Language & Communication Disorders, 49(4), 416-451. doi:10.1111/1460-6984.12102

Tomblin, J. B. (2010). The EpiSLI database: a publicly available database on speech and language. Lang Speech Hear Serv Sch, 41(1), 108-117.

Why eugenics is wrong

I really didn't think I would need to write a blogpost on this topic, but it seems eugenics is having a resurgence in the UK, so here we go.

The idea of eugenics deceptively simple. Given that some traits are heritable, we should identify those with beneficial heritable traits and encourage them to have more children, while discouraging (or even preventing) those with less desirable traits to breed. This way we will improve the human race.

Those promoting eugenics have decided that high intelligence is a desirable trait, and indeed it does correlate with things like good educational outcomes, earnings and health. It is also heritable. So wouldn't it be great to improve the human race by genetic selection for intelligence?

Much of the debate on this question has focussed on whether it could be done, rather than whether it should be. Many who would blench at enforced sterilisation have warmed to the suggestion that Polygenic Risk Scores can be used to predict educational attainment, and so could be used for embryo selection. However, those promoting this idea have exaggerated the predictive power of polygenic scores (see this preprint by Tim Morris for a recent analysis, and this review of Kevin Mitchell's book Innate for other links). But let us suppose for a moment that in the future we could predict an individual's intelligence from a genetic score: would it be acceptable then to use this information to improve the human race?

The flaw in the argument is exposed when you consider the people who are making it. Typically, they are people who do well on intelligence tests. In effect, they are saying "The world needs more people like us". Looking at those advocating eugenic policies, many of us would beg to differ.

The bad state of the world we live in is not caused by unintelligent people. It is caused by intelligent people who have used their abilities to amass disproportionate wealth, manipulate others or elbow them out of the way. Eugenicists should be especially aware that their advantages are due to luck rather than merit, yet they behave as if they deserve them, and fiercely protect them from "people not like us".

If we really wanted to use our knowledge of genetics to make the world a better place, we would select for the traits of kindness and tolerance. Rather than sterilising the unintelligent, we would minimise breeding by those who are characterised by greed and a sense of superiority over other human beings. But there's the catch: it's only those who think they're superior to others who actually want to implement eugenic policies.

Stemming the flood of illegal external examiners

On 21st January, the Times Higher Education published a short piece about Professor Eric Barendt, an academic lawyer at UCL, who had been told that he had to submit his passport to another University in order to be acceptable as an external examiner. He thought this was preposterous, and declined to do so. The reaction on Twitter indicated that passport checks were now widespread in British universities, and many academics were unhappy about it 

My sympathies are with Prof Barendt, and I've decided that I too will not agree to be an external examiner if I am required to provide my passport to prove I am eligible. In fact, a few days after this story broke, I was invited to be an external examiner, and agreed only on condition that I did not have to provide my passport. Alas, it looks like this means I won't be examining the thesis.

This may look like petulance: refusal to comply with what is not an burdensome requirement creates difficulties for a blameless candidate and their supervisor. So let me explain why I think it is important.

External examining is a highly skilled, high-stakes, onerous task for which one is paid not much more than the minimum wage. The going rate varies from institution to institution, but in my recent experience you may get around £180 to £240. You have to read and evaluate a thesis that represents 3 years' worth of work (around 40,000-50,000 words in my discipline), visit the candidate's home institution to conduct an oral examination that lasts around 2-3 hours, ensure that any corrections are done to your satisfaction, and write a report with recommendations. Nobody does this for the money. Rather, like so much in academia, the whole system survives by a quid pro quo: you know that when your own students need examining, you'll want to find external examiners for them. With a strong student, examining can have its own intrinsic rewards, but it can also be highly stressful if there are problems with the thesis. So overall, all of the academics involved in this process know that the external examiner is doing a favour for another institution by agreeing to take on this extra job.

When I first did examining, many years ago, arrangements for selecting examiners were pretty informal. Times change, and everything has got more official and bureaucratic. Many institutions now require external examiners to provide proof of their competence to do the job (a CV and/or list of previous candidates examined), and some have guidelines to avoid too much chumminess between supervisor and external examiner (no co-authorships, for example). I can see that these requirements, have a point in preserving the integrity of the examination system.

But the passport check is really the last straw. It's senseless on two counts. First, it implies that academic institutions classify external examiners as employees, even though they are doing a one-off task for which the pay is trivial. Second, as Prof Barendt noted, it means that they don't trust other academic institutions to do proper checks of right to work. Now, it may be that there are some dodgy places where this is the case, but it seems reasonable to assume that Higher Education Institutions recognised by the Office for Students will be compliant with the law on this point. What is weird is that when I protest about the passport check for external examiners, some colleagues say, "But if the institution didn't do these checks, they'd be liable for enormous fines". Well, given that is the case, then surely it's safe to assume that the institution that actually employs the external examiner will have done the checks. I can understand that institutions might want an option of conducting checks in rare cases where there was reason to doubt this was true. It's the mandatory nature of the checks that are otiose in 99% of cases that is so exasperating.

Some years ago, in a different context, I wrote a piece about expansion of research regulation in academic life. Many of the points I made there apply to this situation. Bureaucracy creeps up on us by a series of stealthy small steps, until we suddenly find ourselves engulfed by it. Yes, showing a passport is a trivial matter, but I think that if we don't resist this kind of thing, it will only get worse.

P.S. Eric Barendt has pointed me to a piece he wrote on this topic for the Oxford Magazine (2020, No. 416, pp 8-10). I don't think this publication is available online, so here is just a short quote from it concerning the legal aspects of passport checks - something that has been discussed on Twitter in response to this blogpost.

An employer breaks the law only if it employs an illegal immigrant, not because it fails to conduct passport checks. If it is confident it is employing a UK national (or other person with a right to work in the UK such as an EEA or Swiss national), then it has nothing to worry about. So an automatic request is unnecessary. It reveals what may be termed a culture of ‘over-compliance’ with government policy. Of course, it is a sensible, indeed a vital, step to take, if a university, or indeed any employer, has doubts about the immigration status of anyone it is contemplating employing, but common sense surely suggests it is quite unwarranted when it engages someone whom it ought to trust.

Another issue tackled by Eric's piece is whether it is reasonable for Universities to treat external examiners as employees:

... it is hard to see why an external examiner, particularly of a doctoral thesis, should be treated as an employee of the host university, when an academic reviewer of a book proposal is not regarded as an employee of the publisher which engaged him (or her) to review it.

It has been suggested on Twitter that if we are to be regarded as employees, we should be paid an appropriate wage, and the post should be advertised!