FOI 24.25 0380 8.RES 226 ASD and DLD diagnoses after 6 years v1.0.pdf

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ASD and DLD diagnoses after 6 years old
The content of this document is OFFICIAL.
Please note:
The research and literature reviews collated by our TAB Research Team are not to be
shared external to the Branch. These are for internal TAB use only and are intended to
assist our advisors with their reasonable and necessary decision-making.
Delegates have access to a wide variety of comprehensive guidance material. If
Delegates require further information on access or planning matters they are to call the
TAPS line for advice. The Research Team are unable to ensure that the information
listed below provides an accurate & up to date snapshot of these matters
Research questions:
1. What are the types of later life developmental disorder diagnoses?
2. What is the incidence of diagnoses for Autism Spectrum Disorder (ASD) and
Developmental Language Disorder (DLD) that occur after the age of 6?
3. What is the incidence of diagnosis for ASD for age groups:
• 0-6
• 7-15
• 16 and above?
4. What is the impact of a later diagnosis on the functional capacity and severity of
symptoms of people diagnosed with ASD or developmental delay?
5. Are there triggers or acute events that precipitate diagnoses?
6. What is the impact of the resolution of an acute event on functional capacity regardless
of diagnosis?
7. Are there therapies / treatments / protocols designed for people with later in life
diagnoses?
8. What is the impact on prevalence of changes to ASD criteria between DSM-IV and
DSM-5?
Date: 15/02/2022
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1. Contents
ASD and DLD diagnoses after 6 years old................................................................................. 1
1.
Contents ....................................................................................................................... 2
2.
Summary ...................................................................................................................... 2
3.
Diagnosing developmental disabilities later in life ......................................................... 3
4.
Developmental Language Disorder............................................................................... 4
5.
Later diagnoses and autism .......................................................................................... 6
5.1  Age of first diagnosis ................................................................................................. 6
5.2  Reasons for later diagnosis ....................................................................................... 7
5.3  Outcomes for people with later diagnoses ................................................................. 8
5.4  Supporting people with later life diagnoses ............................................................... 9
5.5  Effect of DSM-5 on ASD prevalence........................................................................ 10
6.
References ................................................................................................................. 10
7.
Version control ............................................................................................................ 15
2. Summary
Researchers continue to improve early identification methods targeting developmental
disorders. This can reduce the waiting time for children to be diagnosed and for intervention to
begin. In some cases, children do not receive an accurate diagnosis until later childhood or
adolescence. Some are not diagnosed until adulthood. This paper focusses on the incidence
and impact of diagnosing Autism Spectrum Disorder (ASD) and Developmental Language
Disorder (DLD) after the age of 6.
There is limited information directly answering the research questions for an Australian
context. I have gathered information relevant to the research questions which may
approximate answers.
Issues related to overal  prevalence of ASD have been investigated in another TAB research
paper, RES 222 ASD diagnoses.
Types of later life developmental disorder diagnoses
Neurodevelopmental disorders (NDD) are a subset of developmental disorders defined by the
Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5). They are one of the
most common classifications of childhood diagnoses and clinicians aim to diagnose the child
as early as possible. Personal, clinical, social and environmental factors can delay diagnosis.
Incidence of later life diagnoses
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No reliable and comprehensive estimates were found for incidence of later diagnoses of ASD
and DLD nationally or across all age groups. There is evidence that later diagnoses of DLD
are common in people with a history of involvement with youth justice and child protection.
Internationally, the latest systematic review finds the mean age for first diagnosis of ASD is
60.48 months (5 years). However, the best data for Australia suggests mean age of first
diagnosis is 6 years for children diagnosed before the age of 13. This is likely to be
considerably higher if older age groups are incorporated into the estimate.
Events leading to later life diagnoses
There is evidence suggesting personal, social and environmental factors can predict whether
someone will receive a later diagnosis of ASD. However, there is very little evidence
describing events that precipitate a diagnosis. One study suggests adults choose to begin the
assessment process due to encouragement by parents or spouses, difficulties with social
interaction or mental health issues.
Outcomes for people with later life diagnoses
There is evidence establishing the effectiveness of early intervention for people with ASD.
There is less evidence establishing the adverse outcomes for people with later diagnoses
though existing evidence does support the correlation of reduced functional capacity and
increased comorbid conditions in people with later diagnoses. People with missed diagnoses
of DLD are overrepresented in the youth justice and child protection systems.
Supports for people with later life diagnoses
All interventions should be age-appropriate and targeted at the person’s developmental stage.
For older people this may mean interventions targeted at achieving life-stage outcomes such
as employment and independent living. For people with ASD this may also mean accounting
for the likelihood of comorbid conditions.
Prevalence of ASD after DSM-5
Refer to RES 222 ASD diagnoses for further information. The restriction of DSM-5 diagnostic
criteria for ASD has contributed to a reduction in the number of ASD diagnoses even as the
prevalence of ASD continues to rise. The rise in prevalence should be attributed to factors
other than the change in diagnostic criteria in the DSM-5.
3. Diagnosing developmental disabilities later in life
The DSM-5 defines a group of NDDs which begin to manifest early in life and usually before
the child enters school. NDDs can be global (affecting general intelligence or social skills) or
specific (affecting specific aspects of learning or control of executive function) (DSM-5, 2013,
p.31). They include intellectual disabilities, communication disorders, ASD, attention deficit
hyperactivity disorder, specific learning disorder and motor disorders (including movement and
coordination disorders and tic disorders) (p.xiv-xv).
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Diagnosis of NDD is one of the most common types of diagnoses among children. Among
NDDs the most common are learning disorders (8%), DLD (7%), ASD (2%) and ADHD (2%)
(Micai et al, 2020, p.183). Behavioural signs are often observable within the first year of a
child’s life and some indications are known prior to the child’s birth. For example, if the child
has a sibling or other family member with a diagnosis of NDD it increases the risk that they will
also have an NDD (Micai, 2020).
There are several factors that may delay a diagnosis. For example, it may be hard to
determine if a child has social communication deficits until they are in situations which demand
more sophisticated social behaviour. NDDs are often co-occurring, which introduces the risk of
one diagnosis overshadowing other potential conditions and leading to later or missed
diagnoses. Diagnoses can be a lengthy and costly process, which may delay the diagnosis
itself or discourage some parents from beginning the process at all (Valentine et al, 2020;
Micai et al, 2020).
4. Developmental Language Disorder
Many children show significantly slowed language development before the age of three.
However, most of these children catch up to their peers after the age of three allowing them to
perform within normal limits on linguistic tasks. Children who do not catch up may be
diagnosed with DLD (Sansavini et al, 2021, p.2). DLD is the recommended label for language
disorders that are not associated with a specific cause (e.g. autism, down syndrome). The
term Specific language impairment (SLI) has also been used but the applications differ slightly
(McGregor, 2020, pp.39-40). Prevalence of DLD among children is roughly 7% (Walker &
Haddock, 2020, p.2; Ebbels et al, 2016, p.2). A report from the Deeble Institute of Health
Policy states that prevalence among children in Australia may be as high as 17%, with higher
rates in children from disadvantaged backgrounds (Walker & Haddock, 2020, p.2). This
estimate is unreliable. The authors admit the estimate is based on minimal data and they do
not offer an age range for the estimate.
I could not locate information on incidence of diagnoses by age. However, a 2021 review of
systematic reviews suggests that the optimal screening time for DLD is between 2 and 3
years, with a diagnosis expected around 4 years (Sansavini et al, 2021, p.2). However,
evidence is mixed with earlier screening increasing risk of false positives and later screening
increasing risk of negative consequences for the child (p.20).
There is some evidence that DLD is often missed entirely or misdiagnosed in childhood
(McGregor et al, 2020, p.40). A 2013 Australian study of 1607 children found only 45% of
children with communication problems received any help before the age of 5 and only 33%
received speech therapy (Skeat et al, 2014, p.219; Walker & Haddock, 2020, p.4). This does
not differentiate communication problems from DLD specifically and so we can’t
straightforwardly conclude that most children with DLD are undiagnosed. It should also be
noted that this study was prior to NDIS making early intervention available to more families.
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A more recent Australian study of young people leaving ‘out of home’ care found that mean
language scores were 2 standard deviations below the average. This level of deficit is often
used as an indication of DLD. Despite this only a single participant in the study had a
diagnosis relating to language difficulties (Snow et al, 2020, p.155). In another study of 44
young people leaving ‘out of home’ care between 16 and 26 years of age, Clegg et al found
that over 60% met criteria for DLD and yet none had a diagnosis (Clegg et al, 2021, p.2).
Results are similar in a youth justice setting (Snow et al, 2020, p.153; Clegg et al, 2021, p.2)
with Winstanley et al finding 60% of their sample of youth offenders having met criteria for DLD
despite no previous diagnoses (2021, p.399). These findings point to a high rate of unidentified
DLD in young people with involvement of child protection or justice and is consistent with
findings of previous studies that children from disadvantaged backgrounds are more likely to
experience language difficulties (Walker & Haddock, 2020). Because the sample sizes of the
studies were smal and the populations unrepresentative, it is not possible to use them to
reliably estimate prevalence of undiagnosed adolescents or young adults.
According to Walker and Haddock, research into the long-term effects of language impairment
in an Australian context is limited. However:
International longitudinal studies have found that children with language disorders who
do not receive intervention achieve lower levels of education and are subsequently at
higher risk of lower wages and reliance on welfare and of higher levels of redundancy,
under-employment and workplace conflict (2020, p.3).
As of 2016, most studies into the effectiveness of generalised intervention for symptoms of
DLD in school-age children (i.e. children over early intervention age) found no significant
effect. Results were more positive if the treatment group did not have receptive language
difficulties, which are more likely to persist and more difficult to treat. Some positive results for
receptive language skills were found if the interventions were targeted at specific areas, e.g.
receptive vocabulary, word finding, comprehension of specific grammatical structures, etc.
(Ebbels et al, 2016 pp.2-3). Ebbels et al found significant improvement on receptive and
expressive language skills in primary and secondary aged students with DLD receiving 1:1
speech and language therapy (2016, pp.8-9).
Sansavini et al note the consensus in the literature on the importance of early intervention and
diagnosis of DLD (Sansavini et al, 2021, p.14.). A 2021 systematic review of treatment studies
found some evidence for the effectiveness of early intervention on some areas of language
development. Early intervention effects last in the medium term for developing phonological
skills but results of intervention targeting general language skills is mixed (Rinaldi, 2021,
pp.18-19). For example, an Australian study by Wake et al compared the effect of home-based
therapy sessions on children with language disorders with typically developing children. After 2
years they found language abilities for children in the treatment group normalised though they
could not discern a significant effect of therapy sessions on most aspects of language
development, including receptive and expressive language. Some effect was discerned for
phonological awareness with a possible effect on reading ability (Wake et al, 2015, p.843).
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5. Later diagnoses and autism
5.1 Age of first diagnosis
I was able to find only one study using Australian data that tracks age of first diagnosis for
cohorts over 12 years old (Atherton et al, 2021) but this study was based on only 200 people. I
am unable to give a good account of incidence of first diagnosis for the age groups requested.
Two systematic reviews have tracked age at first autism diagnosis between 1990 and 2019.
Daniels and Mandell (2014) reviewed 42 papers published between 1990 and 2012. They
provide a wide mean age range for first diagnosis at between 38 and 120 months. Van t’ Hof et
al (2021) analysed data from 56 studies and found a mean age for first diagnosis of 60.48
months (5 years) with a mean age range of between 30.9 months and 234.57 months (2021,
p.862). The ranges provided by these reviews are significantly affected by age of participants
in the studies reviewed. Many studies included only children, some studies included only older
people. Daniels and Mandell use data from 12 countries. Van t’ Hof et al use data from 40
countries. Both reviews include a single study from Australia (Daniels & Mandell, 2014, p.14-
17; Van t’ Hof, 2021, p.867).
International data indicates that age of diagnosis is decreasing (Daniels & Mandell, 2014, p.6;
Sheldrick et al, 2017; Hanley et al, 2021). This contrasts with a recent UK-based study that
found mean age of diagnosis rose from 9.6 years in 1998 to 14.5 years in 2018 (Russell et al,
2021, p.3). This might be explained by the fact that the Russell et al considered the entire UK
population with an ASD diagnosis whereas the 2015 and 2021 systematic reviews included
mostly studies of children. It may also be explained by regional differences in early intervention
(Daniels & Mandell, 2014, p.10).
I have located 4 studies based on Australian data which discuss age of first diagnosis for ASD.
Nassar et al was included in the Daniels and Mandell systematic review and focused on West
Australian children between 2 and 8 years old. They found the mean age of first diagnosis
decreasing from 4 years to 3 years throughout the 1990s (Nassar et al, 2009, p.1245). A study
from Bent et al was included in the Van t’ Hof systematic review and focused on children under
7 years. They found a mean age of first diagnosis of 49 months (Bent et al, 2015, p.318). May
and Williams (2018) was not included in any of the reviews and looked at children under 13
years. Atherton et al was not included in any of the reviews and looked at 200 adults with ASD
between 18 and 57 years.
According to May and Williams, the average age of diagnosis of children aged 0-12 years old
is 6 years. The average is slightly higher in female children at 6.22 years. This estimate is
based on Medicare data tracking first diagnosis item numbers from 2008 until 2016 and
considers 73,463 children. The most frequent age of diagnosis is 5 until the year 2015/2016
when it lowers to 4 (May & Williams, 2018, p.5). In line with Russell et al (2021), May and
Williams find that the rate of increase of older children being diagnosed is higher than the rate
of increase for children under 5 (2018, pp.4-5). While this study underestimates total
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prevalence due to limitations in the data, it likely captures most diagnoses occurring in this age
range (p.2).
Based on a rough estimate obtained from a study by May and Williams (2018, p.4), for
Australians diagnosed with ASD under the age of 12, 49% were diagnosed under the age of 6
and 51% were diagnosed between 6 and 12 years old. However, these shares will be
significantly different when considering all those diagnosed with ASD in adolescence and
adulthood. The average age of first diagnosis is bound to be higher than 6 when considering
the entire population of Australians with ASD. This indicates that the average age of first
diagnosis is above the early intervention age (>6) (Goodwin et al, 2018, p.2). This would be
consistent with studies of other national populations. Atherton et al found the average age of
diagnosis for their adult cohort was 15 for males and 21 for females (Atherton et al, 2021, p.4).
5.2  Reasons for later diagnosis
The rate of older people being diagnosed with autism is increasing. This appears to be true for
adults (Russell et al, 2021, p.6) and older children (May & Williams, 2018, pp.4-5). Avlund et
al. (2021) identify reasons that children may not receive an ASD diagnosis until later childhood
or adolescence including:
•  symptoms of other developmental disorder overshadow social impairments
•  diagnostic threshold may not be met until it is clearer that the social
demands on the child exceed their abilities
•  the autistic symptoms may be expressed dif erently in early and later
childhood
•  socio-economic factors may influence the support a child receives (Avlund
et al., 2021; Parikh et al, 2018).
A Melbourne based study also identifies limitations on resources as a primary reason that
people do not receive a diagnosis until adolescence. They also note that symptoms being
missed by the school system or primary care physician may result in missed diagnosis
(Aggarwal & Angus, 2015, p.4).
International trends confirm that children are more likely to be diagnosed earlier if they have
more severe autistic symptoms and more likely to be diagnosed later if they have milder
autistic symptoms (Daniels & Mandell, 2014, p.7; Sheldrick et al, 2017 p.8; May & Williams,
2018, p.1; Parikh et al. 2018, p.6; Hanley et al, 2021, p.5; Avlund et al, 2021, pp.3849-3850).
There is also some evidence to suggest that more severe symptoms can delay a diagnosis of
autism if they are interpreted as symptoms of intellectual disability (Avlund et al, 2021, p.3851).
A 2021 study by Atherton et al contrasts with the prevailing opinion, suggesting that people
diagnosed later do not present differently but diagnoses may be missed due to environmental
factors (Atherton et al, 2021, p.6). However, their results are also compatible with a worsening
of symptoms over time in adults lacking proper diagnosis.
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Barriers to adult autism diagnosis may include the following:
•  there are few adult diagnostic screening tools
•  difficulty remembering or recovering early developmental history
•  limited understanding of adult autism in health professionals
•  specialist multi-disciplinary team is often needed
•  it requires significant time and effort from the patient
•  symptoms of other conditions may mask autistic symptoms
•  misdiagnosis or camouflaging of symptoms (Rødgaard et al, 2021, p.5;
Scattoni et al, 2021, p.4130; Adamou et al, 2021, pp.1-2; Lai & Baron-
Cohen, 2015; Legg et al, 2022, p.1).
There is mixed evidence to support these ideas. Rødgaard et al find that misdiagnosis or
overshadowing of other childhood diagnoses may account for some of the reason autism
diagnoses are missed. However, only 31% of males and 39% of females had childhood
diagnoses at all, meaning that misdiagnosis or overshadowing cannot explain why diagnoses
was not given in childhood for most later diagnosed people (2021, p.2).
A 2020 scoping review notes that factors prompting adult diagnosis include encouragement by
parents or spouse, difficulties with social interaction or mental health issues (Huang et al,
2020).
5.3  Outcomes for people with later diagnoses
I could find only a single study that investigates quality of life for people diagnosed with autism
later in life. Atherton et al found that people diagnosed earlier scored better on quality-of-life
measures than people diagnosed later. Increasing age of diagnosis was correlated with
increased social anxiety, social avoidance, and a lack of social support (2021, p.6).
Strong evidence suggests early intervention supports for children with ASD are ef ective in
improving outcomes (Avlund et al, 2021, p.3843; Whitehouse et al, 2020; Productivity
Commission, 2017; Clark et al, 2017, p.2; Zwaigenbaum et al, 2015, p.6; Estes et al. 2015).
When children are diagnosed earlier, they have more access to services and interventions
when their brains are most malleable. This means they can acquire skills from a younger age
and build on these skills through their school years (Clark et al, 2017, pp.1-2).
Clark et al (2017) compared two groups of 7–9-year-olds with earlier or later diagnosis. The
first group received diagnoses at 24 months. The second group received diagnoses between 3
and 5 years old. Those children diagnosed later received interventions later, received
significantly less overall intervention, were slightly less likely to attend mainstream schooling,
received more support at school age, had lower cognitive and language ability and were more
likely to have an intellectual disability. These findings support the idea of improved outcomes
for people diagnosed earlier and reduced functional capacity for people diagnosed later.
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However, considering the ages of the comparison groups, this study may not reflect the
outcomes for people diagnosed after early intervention age (<6 years). On the other hand, the
underlying theory behind the effect is that earlier intervention works by making use of younger
children’s more malleable brains (Clark et al, 2017, pp.1-2; Anderson et al, 2014, p.8). If this is
true then we may predict a similar trend for people diagnosed after early intervention age. As
we found in 4.1 Later diagnosis of autism, this prediction is complicated by confounding factors
such as multiple diagnoses for people with ASD, which may mean that they receive
interventions targeting autistic symptoms even without a diagnosis of ASD.
Adults with autism typically have multiple diagnoses (Pelicano et al, 2020; Keller et al, 2020;
Lai & Baron-Cohen, 2014). Adults with autism have an increased risk of depressive disorders,
anxiety disorders, obsessive-compulsive disorder, attention deficit hyperactivity disorder, and
personality disorders:
•  more than 50% show increased depressive symptoms or depressive
disorder
•  as many as 66% report suicidal thoughts
•  more than 50% may be diagnosed with anxiety disorders
•  up to 40% may be diagnosed with attention deficit hyperactivity disorder
•  up to 30% may be diagnosed with obsessive-compulsive disorder (Lai &
Baron-Cohen, 2014, pp.1018-1019).
This information does not specify age of first diagnosis. However, there is evidence to suggest
that later diagnosed people are more likely to have additional diagnoses (Daniels & Mandell,
2014; Goodwin et al, 2018; Pelicano et al, 2020; Rødgaard et al, 2021). A study of school age
children by Goodwin et al notes that of people diagnosed between 5 and 18 years old, 58%
had a psychiatric diagnosis. Of people diagnosed before 5 years old, only 29% had an
additional diagnosis (Goodwin et al, 2018, p.4). In a smal  qualitative study of late diagnosed
adults with autism, Pelicano et al note that of 28 participants in the study, 16 had at least one
other psychiatric diagnosis and only 4 did not have any other medical condition (Pelicano et al,
2020, pp.21-23).
5.4  Supporting people with later life diagnoses
There is little research of the post-diagnostic needs of adults with ASD (Scatoni, 2021, p.2).
Adults diagnosed with autism later in life have complex reactions and family, friends and
clinicians supporting them should be aware of the potentially life-changing consequences of an
adult diagnosis. In particular, later diagnosed adults and their caregivers report frustration with
lack of post-diagnostic support (Legg et al, 2022, p.2; Scatoni et al, 2021, p.4142).
The UK’s National Institute for Health and Care Excel ence (NICE) has developed a series of
clinical guidelines for people with autism. They recommend supports should be tailored to the
person’s age and developmental level (NICE, 2021a, para. 1.3.1). However the
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recommendations for support do not differ substantially for adults and young people except
regarding their relative levels of autonomy and stages of life. For example, supported
employment programmes (NICE, 2021b, paras. 1.4.11-12) or residential care programmes
(paras. 1.8.11-14) could be considered for adults with autism.
Considering the increased risk of co-morbid diagnoses as described in 5.1 Outcomes for
people with autism, an increased focus on physical and mental health may be warranted. A
2020 systematic review by Benvenides et al found both cognitive behavioural therapy and
mindfulness techniques had an emerging body of evidence as strategies for improving the
health outcomes of older adults with autism. However, there is evidence that both strategies
are also useful for children with autism (Benvenides et al, 2020, p.1351).
5.5 Effect of DSM-5 on ASD prevalence
For more information please refer to RES 222 ASD diagnoses.
A 2019 systematic review investigated the effect of the changes to ASD diagnostic criteria
between the DSM-IV-TR and the DSM-5. They found that approximately 1 in 5 people who
would have received a diagnosis in DSM-IV-TR would not have received a diagnosis in the
DSM-5. Further, only 28.8% of those who no longer meet ASD criteria would go on to meet
diagnostic criteria for Social Communication Disorder (SCD) (Kulage et al, 2019, p.19). This
means roughly 14% of people who met diagnostic criteria under DSM-IV no longer meet
criteria for ASD or SCD. It is unclear what proportion of those people would go on to meet
diagnostic criteria for other conditions and what proportion would remain below threshold for
any DSM-5 diagnosis. According to this review, DSM-5 is contributing to a reduction in ASD
diagnoses while the overall prevalence estimates continue to rise.
6. References
Adamou, M., Jones, S. L., & Wetherhill, S. (2021). Predicting diagnostic outcome in adult
autism spectrum disorder using the autism diagnostic observation schedule, second
edition. BMC Psychiatry, 21(1), 24. doi/10.1186/s12888-020-03028-7
Atherton, G., Edisbury, E., Piovesan, A., & Cross, L. (2021). Autism through the ages: A mixed
methods approach to understanding how age and age of diagnosis affect quality of life.
Journal of Autism and Developmental Disorders. doi/10.1007/s10803-021-05235-x
Aggarwal, S., & Angus, B. (2015). Misdiagnosis versus missed diagnosis: diagnosing autism
spectrum disorder in adolescents. Australasian Psychiatry: Bulletin of Royal Australian
and New Zealand College of Psychiatrists, 23(2), 120–123.
doi/10.1177/1039856214568214
American Psychiatric Association. (2013). Diagnostic and statistical manual of mental
disorders (DSM-5) (5th ed.). American Psychiatric Association Publishing.
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Avlund, S. H., Thomsen, P. H., Schendel, D., Jørgensen, M., Carlsen, A. H., & Clausen, L.
(2021). Factors associated with a delayed autism spectrum disorder diagnosis in
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Bent, C. A., Dissanayake, C., & Barbaro, J. (2015). Mapping the diagnosis of autism spectrum
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Benevides, T. W., Shore, S. M., Andresen, M.-L., Caplan, R., Cook, B., Gassner, D. L., Erves,
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Ebbels, S. H., Wright, L., Brockbank, S., Godfrey, C., Harris, C., Leniston, H., Neary, K., Nicoll,
H., Nicoll, L., Scott, J., & Marić, N. (2017). Effectiveness of 1:1 speech and language
therapy for older children with (developmental) language disorder. International Journal
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6984.12297
Estes, A., Munson, J., Rogers, S. J., Greenson, J., Winter, J., & Dawson, G. (2015). Long-term
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