Prisons, developmental language disorder, and base rates

There's been some interesting discussion on Twitter about the high rate of developmental language disorder (DLD) in the prison population. Some studies give an estimate as high as 50 percent (Anderson et al, 2016), and this has prompted calls for speech-language therapy services to be involved in the working with offenders. Work by Pam Snow and others has documented the difficulties of navigating the justice system if your understanding and ability to express yourself are limited.

This is important work, but I have worried from time to time about the potential for misunderstanding. In particular, if you are a parent of a child with DLD, should you be alarmed at the prospect that your offspring will be incarcerated? So I wanted to give a brief explainer that offers some reassurance.

The simplest way to explain it is to think about gender. I've been delving into the latest national statistics for this post, and found that the UK prison population this year contained 82,314 men, but a mere 4,013 women. That's a staggering difference, but we don't conclude that because most criminals are men, therefore most men are criminals. This is because we have to take into account base rates: the proportion of the general population who are in prison. Another set of government statistics estimates the UK population as around 64.6 million, about half of whom are male, and 81% are adults. So a relatively small proportion of the adult population is in prison, and the numbers of non-criminal men vastly outnumber the number of criminal men.

I did similar sums for DLD, using data from Norbury et al (2016) to estimate a population prevalence of 7% in adult males, and plugging in that relatively high figure of 50% of prisoners with DLD. The figures look like this.

Numbers (in thousands) assuming 7% prevalence of DLD and 50% DLD in prisoners*

As you can see, according to this scenario, the probability of going to prison is much greater for those with DLD than for those without DLD (2.24% DLD vs 0.17% without DLD), but the absolute probability is still very low – 98% of those with DLD will not be incarcerated.

The so-called base rate fallacy is a common error in logical reasoning. It seems natural to conclude that if A is associated with B, then B must be associated with A. Statistically, that is true, but if A is extremely rare, then the likelihood of B given A can be considerably less than the likelihood of A given B.

So I don't think therefore that we need to seek explanations for the apparent inconsistency that's being flagged up on Twitter between rates of incarceration in studies of those with DLD, vs rates of DLD in those who are incarcerated. It could just be the consequence of the low base rate of incarceration.

References
Anderson et al (2016) Language impairments among youth offenders: A systematic review. Children and Youth Services Review, 65, 195-203.

Norbury, C. F.,  et al. (2016). The impact of nonverbal ability on prevalence and clinical presentation of language disorder: evidence from a population study. Journal of Child Psychology and Psychiatry, 57, 1247-1257.

*An R script for generating this figure can be found here.


Postscript - 4th November 2017 
The Twitter discussion has continued and drawn attention to further sources of information on rates of language and related problems in prison populations. Happy to add these here if people can send sources:

Talbot, J. (2008). No One Knows: Report and Final Recommendations. Report by Prison Reform Trust.  

House of Commons Justice Committee (2016) The Treatment of Young Adults in the Criminal Justice System.  Report HC 169.

Labels for unexplained language difficulties in children: We need to talk

The view from the Tower of Babel

This week saw the publication of a special issue of the International Journal of Language and Communication Disorders, focusing on labels for children with unexplained language difficulties. Two target articles, one by Sheena Reilly and colleagues, and one by me, are accompanied by an editorial by Susan Ebbels, twenty commentaries, and a final paper where Sheena and I join forces with Bruce Tomblin to try to synthesise the different viewpoints. These articles are free for anyone to access.

Terminological battles are often boring and seldom come to any consensus, so why are we putting time into this thorny issue? Quite simply, because it really matters. As we argue in the articles, having a label affects how a children are perceived, what help they are offered, and how seriously their problems are taken. 'Specific Language Impairment' has very poor name recognition compared to dyslexia and autism, despite being at least as common. Furthermore, unless we can agree on some common language, it's difficult to make progress in research, and to discover, for instance, the underlying causes of language difficulties, how common they are in different parts of the world, or what interventions work.

I was first confronted with the full extent of the problem when I tried to analyse the amount of research and research funding associated with different developmental disorders (Bishop, 2010). There are other conditions, notably autism and dyslexia, where there is plenty of debate about diagnostic criteria, or even about whether the condition exists. But even so, the terminology is reasonably consistent. For children's language difficulties, this is not the case - they can be described as cases of language difficulty, disorder, impairment, disability, needs or delay, with various prefixes such as 'developmental', 'specific' or 'primary'. Some researchers will use such labels with precise meanings, often excluding children who have co-existing conditions, whereas others use them more descriptively. This made it extremely difficult to do a sensible internet search to estimate the amount of research funding associated with children's language difficulties.  

The confusion over labels has, I think, also contributed to the lack of public recognition of language difficulties in children. A couple of years ago, I joined together with Courtenay Norbury, Maggie Snowling, Gina Conti-Ramsden and Becky Clark with the goal of remedying this situation. We started a campaign for Raising Awareness of Language Learning Impairments (RALLI) (Bishop et al., 2012), and set up a YouTube channel to provide basic information. We spent some time debating what terminology to use: "Language learning impairment" was our preferred choice, but many of our videos talk of Specific Language Impairment, simply because that is a more familiar label. The lack of an agreed label proved a real stumbling block for our attempts at public engagement, and we decided that, as well as producing videos, one of our goals would be to get the terminology issue discussed more widely, in the hope of achieving some consensus. It was a very happy coincidence that Sheena Reilly and colleagues were crystallizing their own position on this question in an article in IJLDC, and that they, and the Editors, were willing to include my article, and the commentaries of other RALLI founders, in the published debate.

One thing that came across when reading commentaries on our articles was the disconnect between research and practice. One point on which I agree with Sheena and colleagues is that there is no justification for drawing a distinction between children whose language problems are comparable with below average nonverbal ability, and those who have a mismatch between good nonverbal skills and low language. Research has failed to find any difference between children with uneven or even nonverbal-verbal profiles in terms of responsiveness to intervention or underlying causes. Such a distinction is, however, widely used in educational and clinical settings to decide which children gain access to extra support in school.  Another issue raised by the Reilly et al paper is whether it is logical to use other exclusionary criteria, and to distinguish, for instance, between children who do and don't have autistic features in association with a language problem.  

As Susan Ebbels noted in her editorial, in everyday settings "diagnostic labels and criteria were being used creatively in disputes over access to services both by those seeking to obtain services for children (often parents and their lawyers) who could be accused of ‘diagnostic shopping’ and also by those seeking to deny services (often due to financial constraints) who may use particularly restrictive criteria in order to reduce the number of children qualifying for services". 

We can't afford to ignore this confused situation any longer. The time has come to have a wider debate on these issues, with the aim of reaching a consensus about how terms are used. The Royal College of Speech and Language Therapists has set up a moderated discussion forum where people can give their views on the best way forward. Please do consider adding your voice: it is important that all those affected by this issue have a say, whether you are a speech-language therapist/pathologist, psychologist, teacher, health professional, legal expert, policymaker, a parent of a child with language difficulties, or someone who has experienced language difficulties. We'd also love to hear from those outside the UK - whether English-speaking or not. You can access the discussion forum here.

Finally, to raise awareness of this debate, during the week of 24th-31st August I will be taking over  the @WeSpeechies Twitter handle as guest curator. On Tuesday 26th at 8.a.m. BST there will be a live twitter debate on this topic. Feel free to join in, even if you aren't a regular tweeter.

References
Bishop, D. (2010). Which Neurodevelopmental Disorders Get Researched and Why? PLoS ONE, 5 (11) DOI: 10.1371/journal.pone.0015112  
Bishop, D., Clark, B., Conti-Ramsden, G., Norbury, C., & Snowling, M. (2012). RALLI: An internet campaign for raising awareness of language learning impairments Child Language Teaching and Therapy, 28 (3), 259-262 DOI: 10.1177/0265659012459467

Slides on this topic are available here.

Addendum Friday 29th August 2014

We've had a great week of interactions on Twitter. A transcript for the week is available here.

I'll look through this and aim to organise the material in due course, but meanwhile would encourage anyone who is interested to continue the discussion on Twitter. I'm appending below some tweets that I generated throughout the week to generate debate.

As noted above, the chat links in to a special issue of the Internat. J Lang. Comm Dis which is free to access here http://t.co/ncTUaYvyoI.  NB it is not all that obvious but there are 10 commentaries after each target article.

If you want to join the discussion on Twitter, feel free to comment at any time, but, please include the #WeSpeechies hashtag, so we can aggregate comments easily. Also if your comment relates to a numbered question, please add Q1, etc so we can relate them.

Monday started with my attempt to summarise each of the  twenty commentaries in a Tweet-length message.

Summaries from commentaries

Paediatricn Gillian Baird: ICD &DSM classifications talk of 'language disorder'; implies distinct from normal variation.  Disorder’ used for conditions without obvious aetiology; functional effect described separately in ICFDH.

Lauchlan/Boyle, ed psych view. Must ask: ‘Will label change the child's life for the better? Aetiology often irrelevant

Bellair et al: community SALTs. No one label works for both research & clinical. SLI has problems but we can manage them.

Mabel Rice: "SLI has yet to receive widespread adoption in clinical practice, in spite of the great need for it." critical of DSM5: excluded "well-researched category of SLI", included SCD, "with a minimal research base"

Kate Taylor SLP. SLI underidentified. Changing the term won't resolve the issue, which is one of measurement rather than label.

Conti-Ramsden: Any Consensus Panel on terminology must be international and include voices from different languages,

Hansson et al: ICD10 labels don't map on to use by researchers in Sweden . : Sweden: phonological & grammatical difficulties seen as part of language impairment. Soc comm probs separate

Clark & Carter: Survey:Scottish SALTs unclear re terms & diagnostic criteria. Move from exclusionary to inclusionary criteria.

Hüneke & Lascelles http://t.co/9rVKJzoBZV. Concern that watering down terminology will mean kids lose scarce resources. Prefer medical term 'developmental dysphasia' that gets problems taken seriously

Strudwick/Bauer http://t.co/GSY5Xwz283 Concern that labels don't capture comorbidities; most ch with 'SLI' have other problems

Michael Rutter, psychiatrist "both clinical & research classifications needed but they require a different approach"

Rutter: Specific’ implies ‘pure’ language impairment; "not supported by any of the available evidence"

Larry Leonard: Many researchers already use broader definition of SLI: do not use term to mean children have a pure profile. communicatn with the public/other disciplines will be even harder if we adopt generic label ‘language impairment.

Snowling: DSM5 treats Communication Disorders separately from Specific Learning Disorders, yet they often co-occur

Aoife Gallagher,SALT; ethical issue:"who owns diagnosis once it has been given.. who ultimately has the right to take it away"

Andrew Whitehouse: ‘SLI’ provides neat criteria for researchers but label hides behavioural & aetiological heterogeneity

Dockrell/Lindsay Educational perspective re SLI is missing yet day-to-day support of learning/development provided by teachers. in England ‘speech, language & communication needs’ (SLCN) indicates primary need is with language & communication

Grist & Hartshorne: http://t.co/QKeQbQFsdy Children & young people we work with rarely describe selves as having SLI or SLCN

Norbury @lilaccourt Relaxing diag criteria will increase demand for services.SALTs shld focus on severe & persistent impairmts

Parsons et al @wordaware Shockwaves through SALT profession if nonverbal IQ criteria and delay/disorder distinction removed .Use of marketing approaches to development of a new term, including consultation with parents & young people.

Wright: legal perspective Much time spent in tribunal appeals arguing re labels: eg is it delay or disorder, is it specific?

Questions for debate

On Tuesday we had a live twitter chat with four question topics, and later in the week, I added further numbered question. Here is the total list – we'd love to hear your thoughts on any or all of these:

Q1 What is your view on use of the diagnostic label SLI? Does it reflect a medical model and is this appropriate.

Q2 is What are appropriate criteria for identifying children's language problems

Q3; Should IQ, ASD features, hearing loss determine whether language-impaired children can access services?

Q4 What terminology is most appropriate for children who have unexplained language problems?

Q5 ICD11 will use'Developmental Language Disorder' and DSM5 uses 'Language Disorder'. What do people think of these terms?

Q6 In research SLI still widely used but without requiring IQ discrepancy. Should we retain SLI but with this broader meaning, or is it just confusing?

Q7 In UK education, Speech, Language and Communication Needs (SLCN) is popular term. Is it used outside UK? Is it useful?

Q8 In UK clinical practice, distinction between language 'delay' & 'disorder' is used, but it has no research support.  Where does delay/disorder distinction come from? How defined?

Q9 Is there any support for a return to the more medical term 'developmental dysphasia'?

Q10. Reilly et al and several commentators suggest we drop 'Specific' and use the term 'Language Impairment' instead .What wld be advantages (e.g. avoids unfair exclusion) and disadvantages (e.g. too broad)?

Q11 What do people think of terms 'Language Learning Impairment' or 'Primary language impairment'? '

Q12 Do diagnostic labels actually help children and families?

Q13 Shld terminology/diagnostic criteria be responsibility of speechies, or shld other professions & families have a say? Assumptions/practices seem v. different in education/medicine/psychology vs speech-language therapy/pathology

Q14 In yr area, who does intervention with kids whose language problems are associated with autism?

Q15 Some  people take pride in identifying themselves as dyslexic. Does this ever happen for kids with language problems? If not, why not?

Q16 Has anyone encountered situation where child not offered intervention bcs language problems attributed to social deprivation?

Q17 Insurance considerations seldom important in UK, but affect label use elsewhere. Do US insurers just require DSM?