Neurodevelopmental disorders: are our

current diagnostic labels fit for purpose?

Dorothy Bishop

Wellcome Principal Research Fellow

Department of Experimental Psychology

University of Oxford

2

Meanings of ‘neurodevelopmental

disorder’

Neurological disorders with known prenatal

cause (genetic or acquired)

e.g. Williams syndrome, fetal alcohol syndrome

Disorders where abnormal neurodevelopment is

inferred: actual cause is complex or unknown

e.g. developmental dyslexia, autistic disorder, specific

language impairment (SLI), developmental

coordination disorder (DCD), developmental

dyscalculia

3

Common characteristics of

neurodevelopmental disorders

Defined in terms of behaviour

Often use medical terminology, drawing parallel

with acquired disorders

Tend to be familial

No single biological cause

Male preponderance in most

4

Do children fall neatly into these

categories?

Kaplan et al, 2001

Developmental co-ordination disorder, 17%

ADHD, 65%

Dyslexia, 70% “Comorbidity is the rule, not the exception”

Gilger and Kaplan, 2001

• Sample of 179 children

and families recruited from

clinics, special schools

• All had dyslexia and/or

ADHD

• Comprehensive

assessment for ADHD,

dyslexia, DCD, and

psychiatric disorders

Dyck, M. J., et al. (2011). The validity of psychiatric diagnoses: The case of

'specific' developmental disorders. Research in Developmental Disabilities,

32(6), 2704-2713.

608 children aged 3 – 14 years 449 Typically-developing

30 Autism spectrum disorder (ASD)

24 Mental retardation (MR)

30 Receptive-expressive language disorder (SLI)

22 Developmental co-ordination disorder (DCD)

53 Attention deficit hyperactivity disorder (ADHD)

Assessments of IQ, language, motor, attention, social cognition, executive function

Western Australian study

Typical

Autism

MR

SLI

DCD

ADHD

Dyck et al: Discriminant function analysis

Same child, different diagnosis

Educational psychologist:

Dyslexia

Speech-language pathologist: SLI

Psychiatrist: Autism spectrum

disorder (ASD)

Neurologist: Developmental

co-ordination disorder (DCD)

Paediatrician: ADHD

Questions

Are these valid diagnostic categories?

What is the impact of labels?

Public perception of diagnostic label

Explanatory force

Symptom complex

Qualitatively distinct from other disorders

Known cause

x

Which is true?

He can’t read because he has dyslexia

Dyslexia is a term applied to children who

find it hard to read for no obvious reason

cf. Erythema

Distinctive symptoms?

Rutter and Yule (1975)

No clustering of the developmental anomalies that are

said to characterize dyslexia.

• "In short, there has been a complete failure to show that

the signs of dyslexia constitute any meaningful pattern."

p 194

• "If there is no recognisable pattern, then in the present

state of knowledge there is no means of determining

whether anyone has the hypothesized condition. Some

kind of biological 'marker' would be needed and so far

none has been found."

Distinctive symptoms?

Stanovich (1994)

Poor readers very similar

cognitive profiles, regardless of

IQ

Same phonological core deficit

in both high and low IQ

DZ twins: share 50% of polymorphic

genes

Question:

Is concordance for disorder higher

in MZ than in DZ twins?

Most studies of dyslexia find YES

Twin Study Method

MZ twins: genetically identical

Twins growing up together are expected to resemble each other

Grigorenko, E. L. (2004). Genetic bases of developmental dyslexia: A

capsule review of heritability estimates. Enfance, 56, 273-288.

15

A recent study shows that variations in a gene called DCDC2 may disrupt

the normal formation of brain circuits that are necessary for fluent

reading, leading to dyslexia. After further research, genetic screening

for these variations could identify affected children early in their

lives and possibly prevent the misdiagnosis of other learning disabilities

that resemble dyslexia.

“We have good statistical data that variations of the DCDC2 gene are

strongly associated with reading disability, also known as dyslexia. These

results reconfirm that dyslexia is strongly genetic and is not a

consequence of just environmental factors,” says lead investigator

Jeffrey Gruen, M.D., Associate Professor of Pediatrics at Yale University

School of Medicine in New Haven, Connecticut.

Copyright: www.CartoonStock.com

So is it like this?

17

High heritability

≠

Single major gene

Genetics: Reality check

DCDC2 is one gene that has been associated

with dyslexia in several studies

Scerri et al (2011) found a SNP on this gene

where the association was significant at p = .005

The risk allele was found in:

• 23% of controls

• 31% of dyslexics

• Most people with the ‘risk’ allele won’t have dyslexia • Most people with dyslexia won’t have the risk variant

100 children

10 dyslexic 90 OK

21 69 3 7

10% dyslexic

23%

Risk variant

31%

Risk variant

With risk variant

General population sample

* *

20

Brain biomarkers

BBC website on Dyslexia

Brain regions found to differ

structurally in dyslexics vs normal readers

cerebellum

(automatisation of skill)

auditory cortex

(hearing)

inferior frontal

gyrus (speech

production)

precentral gyrus (motor control) • Corpus callosum size

• White matter gyral

depth

• Right cerebellum grey

matter

• Auditory cortex size

• Precentral gyrus grey

matter

• Pars triangularis, frontal

lobe, size and shape

• Asymmetry of planum

temporale (> and <)

• Sylvian fissure

length/position

• Temporo-parietal white

matter microstructure

• Relative proportion of

frontal and posterior

cortex N.B. Much within-group variation

Functional brain imaging

Children with

reading disability

display under-

activation of

a network of left-

lateralized areas

during reading,

including

occipito-temporal,

temporo-parietal,

and inferior frontal

cortical regions

Shaywitz, 2003

Cause or consequence of

reading problems?

Experience affects the brain

Dehaene et al, 2010: compared:

31 schooled/literate adults

22 unschooled ex-illiterate adults

10 unschooled illiterate adults

All from Brazil or Portugal

Activation of visual word form area by written words

literate

ex-illiterate

illiterate

Activation of language areas by spoken language

Literate

Ex-illiterate

Illiterate

Implications for functional imaging studies

of dyslexia

Dyslexic-non-

dyslexic differences

could be

consequences of

poor reading, rather

than causes

Public perception of diagnostic label

Explanatory force

Symptom complex

Qualitatively distinct from other disorders

Known cause

x

x

x

x

General issues for neurodevelopmental

disorders

Overlap at behavioural level

Also overlapping causes and neurobiology

ASD

SLI

dyslexia

ADHD

One alternative

Broad category of ‘neurodevelopmental disability’ to

establish need for services

‘Disability’ emphasises impact on individual

‘Neurodevelopmental’ emphasises biological basis: not

just poor teaching

Supplemented with assessment to establish profile of

difficulties/strengths on different dimensions, and

determine which services to prioritise

http://deevybee.blogspot.com.au/2010/12/whats-in-name.html

Advantages

Avoids need for multiple diagnoses

Encourages multidisciplinary assessment

Avoids misleading notions of medical syndrome

Disadvantages

Labels such as dyslexia, autism, ADHD now well-established; provide useful nexus for support groups, etc.

Widespread tendency to assume that if there isn’t a medical label, there isn’t a serious problem

• The problem is just a ‘social construct’ or worse still, an ‘excuse’

Sternberg & Grigorenko

Our Labeled Children (1999)

Schools have financial interest in identifying

specific learning disabilities

Teachers “let off the hook”; "Often, the problem

is not what is being taught but how it is being

taught"

“.. diagnosis as it now exists has provided some

children who seem to be underachieving, based

on their socioeconomic status, a way out"

Labels can be helpful: but how to

choose them?

A tale of two disorders

DEVELOPMENTAL DYSLEXIA

Unexpected difficulty in

learning to read

Not explained by lack of

opportunity to learn

Not explained by

visual/hearing problems, low

IQ

Not due to brain damage or

known syndrome

(SPECIFIC READING DISABILITY)

Prevalence 5-10%

SPECIFIC LANGUAGE IMPAIRMENT

Unexpected difficulty in learning to talk

Not explained by lack of opportunity to learn

Not explained by visual/hearing problems, low IQ

Not due to brain damage or known syndrome

(DEVELOPMENTAL DYSPHASIA)

Prevalence 3-7%

Kamhi, A. G. (2004). A meme's eye view of speech-language

pathology. Language Speech and Hearing Services in Schools,

35(2), 105-111.

“Why is it more desirable to have dyslexia than to

have a reading disability?

Why does no one other than speech-language

pathologists and related professionals seem to know

what a language disorder is?

Why is Asperger’s syndrome, a relatively new disorder,

already familiar to many people?”

Dyslexia/SLI – good and poor memes

Memes: What Are They?

“Examples of memes are tunes, ideas,

catch-phrases, clothes fashions, ways of

making pots or of building arches. Just

as genes propagate themselves in the

gene pool by leaping from body to body

via sperms or eggs, so memes

propagate themselves in the meme pool

by leaping from brain to brain via a

process which, in the broad sense, can

be called imitation.”

R. Dawkins

Successful meme

Easy to understand, remember, and

communicate to others:

May be influenced by whether confers

advantage to the person communicating

Survival does not depend on whether they

are useful, true, or potentially harmful

1985-1989 1990-1994 1995-1999 2000-2004 2005-2009

Dyslexia

Specific reading disability

Specific reading retardation (Rutter & Yule)

Developmental reading disorder (DSMIV)

Dyslexia has survived many attacks!

Terminology in published papers

Amount of research (1985-2009) and prevalence

of neurodevelopmental disorders

Condition

papers

/year

freq.

%

Tourette syndrome 83 0.5

Autistic spectrum disorder 643 0.7

Developmental dyscalculia 9 3.0

Attention deficit hyperactivity disorder 505 5.0

Developmental dyslexia 152 6.0

Developmental coordination disorder 16 6.5

Specific language impairment 46 7.4

Bishop, D. V. M. (2010). Which neurodevelopmental disorders get

researched and why? PLOS One, 5(11), e15112. doi:

10.1371/journal.pone.0015112

44

Research funding and frequency of

neurodevelopmental disorders

Condition

NIH spend $

2000-2009 freq. %

Tourette syndrome 252,709,203 0.5

Autistic spectrum disorder 2,613,298,181 0.7

Developmental dyscalculia 4,355,095 3.0

Attention deficit hyperactivity disorder 2,205,461,058 5.0

Developmental dyslexia 136,012,937 6.0

Developmental coordination disorder 4,093,060 6.5

Specific language impairment 125,035,522 7.4

Labels have consequences

Medical-sounding labels get taken seriously

Conditions with medical-sounding labels attract more research funds • But not always successful: dyscalculia and dyspraxia

have not been successful memes

• May also depend on the professional group with principal responsibility (power, gender)

And a good meme may include or even induce positive features of disorder

Positive connotations of labels

Henry Winkler

So as I’m reading the narration into

a tape recorder, it started

to dawn on me. I’m not lazy. I’m not

stupid. I’m dyslexic!”

neurodiversity.com

Autism in Positive Light

In conclusion

Naïve to imagine we could abandon terms such as ‘dyslexia’ Adverse consequences would include:

Fewer children having problems recognised

Increase in tendency to blame all problems on poor parenting/schooling

Less research into biological bases

But need to be aware this (and other neurodevelopmental disorders!) is a fuzzy category, and does not explain anything

Children need multidisciplinary assessment

Question of what to do about ‘cinderella’ conditions: SLI, dyscalculia, dyspraxia

Raising Awareness of Language Learning Impairments

http://www.youtube.com/RALLIcampaign

Dorothy Bishop

Oxford Study of Children’s

Communication Impairments,

Department of Experimental

Psychology,

South Parks Road,

Oxford,

OX1 3UD,

England.

dorothy.bishop@psy.ox.ac.uk