Differences of Symptom Distribution Across Adult Age in High Functioning Individuals on the Autism Spectrum Using Subscales of the Autism Spectrum Quotient
Journal of Autism and Developmental Disorders
Differences of Symptom Distribution Across Adult Age in High Functioning Individuals on the Autism Spectrum Using Subscales of the Autism Spectrum Quotient
Rob Siebes 0 1 2 3
JanW‑illem Muntjewerff 0 1 2 3
Wouter Staal 0 1 2 3
0 BuurtzorgT , Nijmegen , The Netherlands
1 Department of Psychiatry, Radboud University Medical Centre , Nijmegen , The Netherlands
2 Karakter Child and Adolescent Psychiatry University Centre , Reinier Postlaan 12, 6525 GC Nijmegen , The Netherlands
3 Facculty of Social Sciences, Leiden University , Leiden , The Netherlands
Little is known about the distribution of symptoms of Autism Spectrum Disorder (ASD) across the lifespan. In this crosssectional study, we examined differences between subscales of the Autism Spectrum Quotient (AQ) between different age groups. 654 Subjects referred to an outpatient University Clinic with specialized expertise in ASD were included. Data collection, including self-report and report by spouses, was performed from 2008 to 2014. Results show no significant differences between the different age groups. AQ scores based on self-report corresponded remarkably well with those from their spouses. In conclusion, the main traits of an ASD appear stable between the different age groups. Also, the results show that using the AQ, patients have largely the same appreciation of symptoms as their spouses.
Autism Spectrum Quotient (AQ); Subscales; Age groups; Adults
Studies on Distribution of Symptoms Between
Different Age Groups from Child to Adult Life
Autism spectrum disorder (ASD) is a lifelong
developmental disability with a prevalence which is hard to measure
because of its chronical nature. Earlier prevalence estimates
were lower, centering at about 0.5 per 1000 for autism
during the 1960s and 1970s as opposed more recent reports
of 1–2 per 1000, which may be related to changes in
diagnostic practices, referral patterns, availability of services,
age at diagnosis, and public awareness
(Newschaffer et al.
. Symptoms of autism include social and
communication impairment and restricted repetitive and stereotyped
patterns of behaviour, interests and activities. In a normal
population autistic traits are relatively stable from childhood
(Taylor et al. 2017)
. The triad of symptoms
in people with ASD seems to decrease with age
et al. 2014)
, but little is known about the distribution of
symptoms between different age groups, both in clinical and
non-clinical. Autism in childhood has been well described,
but the symptomatology in later age groups has been little
subject of investigation, especially for the group of adults
with high functioning autism (HFA), or Asperger’s
syndrome. It appears that symptom trajectories have
considerable individual variation, and should be viewed from a
developmental perspective. More at group level, adolescents
and young adults may improve more in social interaction
than in the Restricted, Repetitive Behaviors and Interests
(Seltzer et al. 2003)
The ideal model to explore symptom changes over a
longer period of time would be a longitudinal study with
valid symptom measures. No such study has been performed,
which is not surprising given the efforts that it would take.
A way to shed some light on this, is to perform a study with
cross-sectional symptom measures in different age cohorts.
This of course will not provide individual trajectories, but
may increase our understanding to some extent. The
purpose of this article is to describe the distribution in symptom
(clusters) between the different age groups of individuals
with HFA using the subscales of the autism quotient (AQ).
We hypothesize that the later adult age groups respectively
have more problems in repetitive and stereotyped patterns
of behaviour than the domains of communication and social
Only few studies investigated the distribution of
symptoms of individuals with ASD into adulthood. Reviews on
the outcomes of children, adolescent and adults with ASD
mainly describe results from studies that are mostly
conducted on cognitive and social outcomes
(Howlin et al.
2014; Levy and Perry 2011; Magiati et al. 2014; Seltzer
et al. 2004)
. Most of these studies have large variation in
IQ scores and small variation in age. They mostly cover a
small period in life, and are retrospective using the ADI-R
(Autism Diagnostic Interview, Revised). To our knowledge,
no studies have been conducted that explore the
distribution of symptoms between different adult age groups, which
is unfortunate since the clinical importance of providing
insight differences in symptomatology between different age
groups is evident. The longest follow up study by Howlin
et al. (2014), is the only study where a large population of
individuals with HFA were followed into late adulthood.
This study was mainly focused on cognitive development
and social outcomes, but it also describes the development
of symptoms after a period of 40 years using the ADI-R.
Overall, this study showed a general improvement in autism
symptomatology with age. A subgroup which was also
assessed 20 years earlier (mean age 26) showed that social
outcomes after 40 years of follow up were poorer than the
assessment at younger adulthood.
Billstedt et al. (2007
) followed a population with a
childhood diagnosis of ASD for a period of 13–22 years using the
Diagnostic Interview for Social and Communication
Disorders (DISCO). A large proportion of the included
individuals suffered from intellectual disability. In that study it was
found that various types of symptoms in the social
interaction category were still common whereas communication
problems were much less pronounced on follow-up.
Behavioural impairments were much more variable in adulthood.
Only one single symptom from this category, maintenance
of sameness in routines, was reported to be present in half
or more of the study group at the follow-up study.
Apart from these longitudinal studies, several
retrospective studies have been published, with mixed designs and
patient samples. In a retrospective study by Seltzer et al.
(2003) showed that adolescents are more likely to improve in
reciprocal social interaction domain than adults, whereas the
adults were more likely to improve in the restricted,
repetitive behaviours and interests. No differences in severity of
symptoms between cohorts in the communication domain
were found. However, no levels of IQ were reported in this
study. The authors speculated about the possibility that
the developmental course of the abnormal behaviours of
autism is one of abatement of symptoms from adolescence
into adulthood. On the other hand, their adolescent cohort
appeared to be less impaired than the adult cohort in the
manifestation of prosocial behaviours, such as
communication and social interaction.
Other follow up studies have been performed in
childhood, including a study by
Gillespie-Lynch et al. (2012
It was found that improvements on social domain occur
with increased age, but that only minor changes occur with
respect to non-verbal communication and
repetitive/stereotyped symptoms. Additionally, a study by
and Sigman (2005)
suggested improvement in all domains,
with high functioning participants showing more extensive
improvements. Studies on the transition of adolescence to
adulthood found some improvements in restricted repetitive
(Chowdhury et al. 2010)
found that autism symptoms and
maladaptive behaviours were generally improving with age during
secondary school, but this improvement slowed down
significantly after high school exit.
Overall, it remains unclear whether there are differences
of symptom distribution in patients with an ASD,
especially in late adulthood. A possibility to investigate this is
to use the autism spectrum quotient, which is an efficient
instrument for assessing and quantifying autistic traits in
Autism Spectrum Quotient (AQ)
The AQ is a questionnaire, which can be used as
selfreported or reported by a close relative (AQ-adolescent and
AQ-child), was originally developed to identify ASD among
adults with normal intelligence
(Baron-Cohen et al. 2001)
is translated and validated in Dutch, Japanese, Polish,
Australian and Canadian populations
(Broadbent et al. 2013;
Hoekstra et al. 2008; Lepage et al. 2009; Pisula et al. 2013;
Wakabayashi et al. 2006)
. The AQ contains five
theoretically defined subscales of autistic behaviour; social skills,
attention switching, attention to detail, communication and
The AQ consist of 50 items, 10 items per subscale.
Original cut-off score
(Baron-Cohen et al. 2001)
is 32 points,
however this cut-off differs per study group. It also
quantifies autistic traits in adolescents and children with HFA
or Asperger Syndrome (AS)
(Auyeung et al. 2008;
BaronCohen et al. 2006; Sonie et al. 2013)
. In adolescents and
children the AQ is completed by a parent report. For spouses
of patients the AQ has not yet been validated yet, although
the AQ appears to have high face validity for such a use.
One study of Wakabayashi et al. (2006) were the AQ was
reduced to a 40 item questionnaire for parents (by 32AS/
HFA and parent pairs), shows a mean difference of 2.1
points (SD = 0.5), if the self-reported AQ is compared to
the parent reported AQ on these 40 items.
Studies of the use of the AQ in the clinical practice show
Woodbury-Smith et al. (2005
) found that
the AQ is strongly predictive who receives a diagnosis of
ASD in adults with AS with normal intelligence and high
functioning autism. The cut-off score with the best
specificity and sensitivity was 26 out of a total of 50 items. In a
Sizoo et al. (2015
) found that the AQ has no
sufficient validity to reliably predict a diagnosis of autism
spectrum disorder in outpatient settings.
While the AQ may be less sensitive in HFA for predicting
an ASD diagnosis, it appears a valuable tool for assessing
and quantifying symptoms of ASD at different ages. In the
present study, we therefore used the AQ to measure ASD
symptoms at different age stages in order to provide the field
with a better understanding of symptom distributions during
Also, the AQ was used to evaluate the appreciation of
symptoms of ASD patients compared to their spouses.
AQ questionnaires obtained of patients referred to an
outpatient University Clinic (Radboud University
Hospital, Department of Psychiatry) from 2008 to 2014 were
analysed. AQ data, including self-reported and reports by
spouses of 878 patients were obtained. 472 spouses filled out
the AQ, and 562 patients filled out the self-reported AQ. Of
380 patients both AQ’s where available. Following clinical
assessment by a team of ASD experts 654 were diagnosed
with an ASD (471 male; 183 female), 195 were between
18 and 30 years of age, 139 between 30 and 40 years, 227
between 40 and 50 years, 151 between 50 and 60 years of
age and 65 were older than 60 years of age. DSM-IV
classifications were established after a developmental history
was taken, in most cases a parent interview, in cases where
no parents were available, an interview took place with a
close relative. Furthermore an examination by a psychiatrist
was performed, and if there still were uncertainties about
the diagnosis, an Autism Diagnostic Observation Scheme
(ADOS) was performed. The autism quotient questionnaire
was a standard instrument used in the diagnostic procedure,
both self-reported and parent-reported. Co-morbidity like
Attention Deficit Hyperactivity Disorder (ADHD) and
personality disorders were not excluded for this study. The
distribution between the different subscales and the total score
on the AQ of five age groups was investigated (Table 1). The
items “attention to detail” and “attention switching” were
used to relate to repetitive and stereotyped behavior.
All calculations were performed with the SPSS software
package, version 23. The means of the different AQ
subscales and total AQ scores of different age groups were
normally distributed and compared using ANOVA, with a p
value of 0.05.
No significant differences between the subscales for
restricted repetitive and stereotyped patterns of behaviour
(attention to detail and attention switching) and the other
subscales representing communication and social
interaction were found. On the subscale of imagination there was
a significant difference between the different age groups,
especially between the group of 18–30 years and > 60 years.
This, however, was not the focus of this investigation.
Significant differences were found between the subscales
and total AQ between the self-reported AQ’s and the AQ
reported by spouses, except for the imagination subscales
and the communication and social skills subscales reported
by spouses (Table 1). For example: the total AQ scores of the
self-reported group were 30.59 (SD 8.80) these of the group
reported by spouses were 32.69 (SD 7.73) (Table 1). The
differences, however, are too little to be of clinical relevance,
Fig. 1 Correlation of AQ
score self-report and AQ score
reported by spouses
the AQ scores based on self-report corresponded actually
remarkably well with those from their spouses. Significant
correlations were found between the self-reported AQ scores
and these reported by spouses (Fig. 1).
This study shows two major findings. First, the main traits
of an ASD in patients referred to an outpatient University
clinic, as represented by the subscales of the AQ, are stable
between the different adult age groups. The big strength of
this study is that this was found in a large cohort of patients.
This indicates that the distribution of symptoms is stable
during adult life. However this does not mean that the
problems experienced by these symptoms are equal per age
group. Clinically this finding indicates that autism experts
should take into account that basic principles of
interventions which are effective in younger age groups can also be
applied in later age groups. However, our study is based on
referrals as is custom in the Health Care system in The
Netherlands. Variations between countries are considerable, and
our advises should be tailored to the organization of Health
Care per country.
This all implies that the hypothesis that differences
between groups at different ages, would be found for social
and communication domains, but not for the repetitive and
restrictive behaviours, could not be supported.
Second, high correlations were found between the AQ
scores of patients and their spouses, even though the main
AQ scores marginally, but significantly differ between
them. As a group, patients and spouses see a remarkably
equal pattern of symptoms. Spouses seem to be capable
to do reliable observations of symptoms of their relatives.
Both spouses and patients do score above the cut-off score
of 26 as proposed in the clinical study of
et al. (2005
). This could indicate that the AQ can also be
used as a questionnaire reported by spouses, which already
has been validated in an adolescent and child’s group, but,
to our knowledge, has never been validated for the adult
group. In this way the AQ, reported by spouses, can be of
extra value in the screening procedure for an ASD.
However, first a validation study is necessary.
The most important limitation of the study is that it is
not longitudinal. Nothing can be concluded about the
differences in symptom distribution during the life-span of
patients with ASD.
Furthermore the included patients were referred to a
university hospital; clinically this can be a selection of
patients. Also it is not representative for the general
population. Not all questionnaires were completed by both
patients and spouses. Sometimes no spouses were
available, or questionnaires were not submitted for the
datacollection. Nevertheless there were a substantial number
of 380 patients were both questionnaires were filled in.
The cohorts of patients older than 70 years are relatively
small in comparison to the other groups.
A further limitation is that the AQ has not the validity
that it can be used as a diagnostic tool, it is validated as a
screenings instrument. It is not clear if the subscales can
be used to compare the different symptom clusters between
different age groups. Since there is very little information
on the differences of symptoms between different ages,
this study tries to add more information on the subject
using these subscales on the AQ.
It is unclear what can be concluded form the significant
difference between the imagination subscale between the
younger and older age groups, in which older age groups
have higher scores on the imagination subscales than
younger age groups. It could be possible that this is a
normal variance between age groups, although this had never
It can be discussed whether attention to detail and
attention switching relate to stereotypic and repetitive
behaviors. Previous studies have shown that inhibitory control
and attentional flexibility predicts stereotyped behavior in
(Mostert-Kerckhoffs et al. 2015)
Overall, the conclusions of this study are that the
symptoms of the group of patients included are stable between
the different adult age groups. Furthermore the AQ scores
of patients and spouses are remarkably comparable. It is
interesting to investigate the distribution of symptoms
during life using the AQ, but therefore a longitudinal study is
necessary. In such a study the level of functioning of the
participants should also be included.
Author Contributions RS, JM & WS conceived of the study,
participated in its design, and drafted the manuscript; RS performed data
collection and statistical analysis.
Compliance with Ethical Standards
Conflict of interest Rob Siebes, Jan-Willem Muntjewerff and Wouter
Staal declares that they have no conflict of interest.
Ethical Approval This article does not contain any studies with human
participants or animals performed by any of the authors. Data
collection was part of a routine clinical procedure.
Open Access This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://creativeco
mmons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided you give appropriate
credit to the original author(s) and the source, provide a link to the
Creative Commons license, and indicate if changes were made.
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