Is Older Age Associated with Higher Self- and Other-Rated ASD Characteristics?
Journal of Autism and Developmental Disorders
Is Older Age Associated with Higher Self- and Other-Rated ASD Characteristics?
Anne G. Lever 0 1 2
Hilde M. Geurts 0 1 2
0 Present Address: Dimence , Deventer , The Netherlands
1 Present Address: Department of Psychiatry, VU Medical Center , Amsterdam , The Netherlands
2 Dr. Leo Kannerhuis, Research Development & Innovation , Doorwerth , The Netherlands
3 Hilde M. Geurts
Autism spectrum disorder (ASD) characteristics seem to abate over time, but whether this protracts until late adulthood is largely unknown. We cross-sectionally investigated self- and other-reported ASD characteristics of adults with (ASD: Nmax-self = 237, Nmax-other = 130) and without ASD (COM: Nmax-self = 198, Nmax-other = 148) aged 19-79 years. Within the ASD group, self-reported ASD characteristics, and sensory sensitivities were highest in middle adulthood, while age was not associated to empathy. Sex differences were also found. However, age-and sex-related differences were not revealed by others and self- and other-report were poorly concordant. These results show that ASD characteristics in adulthood are differently perceived across age, sex, and informants and suggest that it is important to repeatedly assess self-reported ASD characteristics during adulthood.
Autism spectrum disorder; Self- and other-report; Autism traits; Aging; Adulthood; Symptomatology
Although autism spectrum disorder (ASD) is considered a
lifelong condition, there is evidence that behavioral ASD
characteristics may abate over time
(Magiati et al. 2014;
Seltzer et al. 2004)
. For example, studies in children and
young adults with ASD revealed that some might no longer
meet ASD diagnostic criteria
(Helles et al. 2016; Louwerse
et al. 2015)
. This suggests that ASD characteristics and,
potentially, the experienced associated impairments can
actually change across the lifespan (Geurts and Jansen 2012;
Electronic supplementary material The online version of this
supplementary material, which is available to authorized users.
Department of Psychology, Dutch Autism and ADHD
Research Center, University of Amsterdam, Nieuwe
Achtergracht 129B, 1018 WS Amsterdam, The Netherlands
Happé et al. 2016; Howlin et al. 2013;
Piven et al. 1996
Knowledge on behavioral ASD characteristics in middle
and late adulthood is, however, still limited, even though
critical in elucidating the magnitude and specificity of
agerelated differences and for recognizing ASD in (late)
(e.g., Happé and Charlton 2012; Hategan et al. 2016;
Perkins and Berkman 2012; Piven and Rabins 2011; Wright
et al. 2013, 2016)
The few studies that do include mid- and/or old aged
ASD adults present contradictory findings
et al. 2011; Bishop and Seltzer 2012; Esbensen et al. 2009;
Happé et al. 2016; Howlin et al. 2013; Shattuck et al. 2007)
For example, it has been reported that ASD characteristics
become less severe over time
(e.g., Howlin et al. 2013)
also that older age was associated with higher ratings of
(e.g., Happé et al. 2016)
. There are a wide range
of methodological differences (for example, respectively
longitudinal, childhood ASD diagnoses, DSM-III criteria,
and other-reports versus cross-sectional, adulthood ASD
diagnoses, DSM-IV and DSM-V criteria, and self-reports)
between these two studies which each could serve as valid
explanations for the differences in observed findings.
Furthermore, whether age-related differences in ASD
characteristics are observed might depend on whether one focuses
on specific ASD subdomains
(e.g., Howlin et al. 2013)
general ASD characteristics to get an overall picture
Happé et al. 2016)
For example, Shattuck et al. (2007) examined changes in
other-reported ASD characteristics over a 4.5 years period
among ASD individuals aged 10–52 years. Overall, while
nonverbal communication impairments remained stable and
symptoms of verbal communication and social reciprocity
ameliorated, improvement was especially observed in the
repetitive behavior domain. Similarly, other-reported ASD
severity decreased over an approximately 37 years period
(age range at follow-up 29–64 years), with, again, significant
improvement on the restricted, repetitive behavior domain
(Howlin et al. 2013)
. This is in line with the finding that
older individuals with ASD (until 62 years) displayed fewer
and less severe repetitive behaviors than younger
individuals as reported by other informants
(Esbensen et al. 2009)
Regarding sensory sensitivity, newly relevant in the DSM-V
(American Psychiatric Association 2013)
sensory symptoms were not associated with age in the broad
general population (range 16–65 years)
nor in adults with ASD (18–65 years)
et al. 2009)
. Anecdotal accounts also indicated that sensory
symptoms do not seem to abate, although people might be
better able to cope with them
, which might
explain why parents reported age-related improvements
(Kern et al. 2006; Shattuck et al. 2007)
selfreport. Regarding social behavioral characteristics, older
adults were socially more adjusted than younger adults
(range 18–54 years) according to both self and another
informant, even though age was not related to observed
(Bastiaansen et al. 2011)
Even studies with apparently similar methods may display
contradictory findings. For example, age was
et al. 2016)
or was not
(e.g., Bishop and Seltzer 2012; De
la Marche et al. 2015)
related to general self-reported ASD
traits among adults. In a recent report of ASD adults,
predominantly aged between 18 and 55 years, older age was
associated with higher ratings of ASD traits including traits
related to social symptomatology (Happé et al. 2016). While
this observation might be explained by the recently obtained
adulthood ASD diagnoses of the participants, the authors
hypothesized that this could also be due to an age-related
improvement in the insight in one’s own functioning. If this
is indeed the case, a similar age-related association might be
absent when other informants rate ASD-symptomatology. In
sum, repetitive behaviors seem to mitigate with increasing
age, whereas the findings of other ASD symptom domains
are less consistent which might partly be informant related.
A common characteristic of most of the aforementioned
ASD studies is that the number of participants over the age
of 55 years was relatively small or non-existent. This is
relevant as we recently showed that psychiatric
(Lever and Geurts 2016b)
in adults with ASD differs
between older individuals (aged 55–79 years) and slightly
younger individuals with ASD (aged 39–54 years). The
presence of psychiatric comorbidities was lower in the older than
in the younger group, but almost similar to those that were
much younger (aged 19–38 years). Moreover, in a general
cross-sectional sample both cognitive and affective
components of empathy increased from young to middle adulthood
and declined in late adulthood (O’Brien et al. 2013). This
is of relevance for ASD as ASD individuals are thought to
have problems with cognitive empathy rather than
(Jones et al. 2010)
. These empathy difficulties
are often related to the social challenges ASD individuals
experience in daily life. Inverted U-shapes (i.e., an increase
followed by a decrease) will be missed if hardly any older
participants are included when determining lifespan ASD
As mentioned, inconsistencies between age-related
findings could be related to who is the informant providing
information. Direct comparisons of the ratings of different
informants indicate that informants generally disagree on
(e.g., Achenbach et al. 2005;
Kooij et al. 2008; Samuel et al. 2016; van der Ende et al.
. Differences between adult informants in ASD
symptomatology have also been found
(e.g., Baron-Cohen et al.
2001; Möricke et al. 2016)
. However, inter-rater
correlations between self- and other ASD reports in adults have
been considered satisfactory
(e.g., Baron-Cohen et al. 2001;
Noens et al. 2012)
and agreement between self and others
has been found to be moderate on social responsiveness (De
la Marche et al. 2015).
The primary goal of the current cross-sectional study is
to test the association between age and ASD characteristics,
including empathy and sensory sensitivity, in adults aged
19–79 years. The current research set-up is highly similar to
the recent Happé study (2016) as the majority of the
participants have an adulthood diagnosis of ASD, have an (above)
average intelligence, and the general ASD traits [i.e.,
autismspectrum quotient (AQ)] measure included is exactly the
same. Therefore, we expect to replicate the finding that older
age is associated with increased ASD self-reports, at least in
those aged between 19 and 55.1 Moreover, we hypothesize
higher ratings of cognitive and affective empathy up to mid
age followed by lower ratings in late adulthood (inverted
1 Please note that when we designed the study we actually expected
a decrease in overall ASD symptomatology in the ASD group and
not in the control group given (a) the previous findings using
different measures that with increasing age there was a decrease in ASD
symptomatology in those with ASD
(Seltzer et al. 2004)
; and (b) that
with the same measure in the general population no association with
age was observed
(Hoekstra et al. 2008)
. Our hypothesis changed due
to the recent findings by Happé et al. (2016) and our own recent
psychiatric comorbidity findings
(Lever and Geurts 2016b)
U-shape) and no relationship between age and sensory
sensitivity. Furthermore, the role of sex is explored given the
often observed symptomatic differences between males and
(Baron-Cohen et al. 2014; Hull et al. 2017; Lai et al.
2011; Ruzich et al. 2015; but see, van Wijngaarden-Cremers
et al. 2014)
The secondary goal of the current paper is to compare
self- and other-reported ASD characteristics. We test
whether age- and sex-related findings are differently reported
by informants, as this could be hypothesized based on
previous studies. Furthermore, in line a much smaller study with
an adult sample
(De la Marche et al. 2015)
, we expect the
agreement between self- and other-reports to be moderate.
Individuals with ASD aged 19–79 years were recruited
through several mental health institutions across the
Netherlands and by means of advertisement on client
organization websites. Requirement upon study participation was to
have a clinical ASD diagnosis based on DSM-IV criteria
(autism, Asperger’s syndrome, and Pervasive
Developmental Disorder Not Otherwise Specified)
Psychiatric Association 2000)
, which was generally established
by a multidisciplinary team including a psychiatrist and/or
psychologist. Individuals without ASD [comparison group
(COM)] were recruited by means of advertisement on the
university website and social media and within the social
environment of the experimenters. Controls were eligible
for participation when a clinical diagnosis of ASD, attention
deficit hyperactivity disorder (ADHD), schizophrenia and
close relatives suffering from ASD or schizophrenia were
absent. Based on these criteria we excluded four individuals
with ASD and nine individuals without ASD, resulting in a
sample of 440 participants (241 ASD, 199 COM). See for a
detailed participants description also the Lever and Geurts
(2016b) paper focusing on comorbidity in adults with ASD
as here we largely included the same participants.
Of this sample of 440 participants, 435 participants
completed the AQ (nASD = 237, nCOM = 198), 349 the
Interpersonal Reactivity Index (IRI) (nASD = 172, nCOM = 177) and
336 the sensory sensitivity questionnaire (SSQ) (nASD = 163,
nCOM = 173). Two-hundred-eighty-five participants returned
one or more questionnaires filled out by an informant
(e.g., this could be a partner, family member, or friend).
Please note that the number of other-SSQs is by
definition smaller than both the AQs and IRIs due to the later
addition of the SSQ to the set of questionnaires. In total,
270 AQs (nASD = 125, nCOM = 145), 278 IRIs (nASD = 130,
nCOM = 148), and 141 SSQs (nASD = 65, nCOM = 76) were
completed. In a subset of the sample, the Autism
Diagnostic Observation Schedule module 4
(ADOS; de Bildt and de
Jonge 2008; Lord et al. 2000)
(nASD = 142) was administered
to have more detailed information regarding current ASD
related symptomatology, IQ was estimated with a short
version of the Wechsler Adult Intelligence Scale third edition
(Uterwijk 2000; Wechsler 1997)
(nASD = 142, nCOM = 180),
and comorbidity was measured with self-reports and
(see Lever and Geurts 2016b for details)
In this subset, eligible ASD individuals were selected based
on age and sex to ascertain that participants were evenly
distributed across ages and sex until a predefined number of
participants needed was reached.
Autism-Spectrum Quotient (AQ)
The Dutch version of the AQ
(Baron-Cohen et al. 2001;
Hoekstra et al. 2008; Ruzich et al. 2015; Woodbury-Smith
et al. 2005)
was administered to identify the degree to which
an intellectually able adult show ASD traits.2 This
selfreport questionnaire consists of 50 statements about core
ASD-related characteristics and assesses five different areas:
social skills, attention switching, attention to detail,
communication, and imagination. Each statement is rated with 1
“definitely agree”, 2 “slightly agree”, 3 “slightly disagree”,
and 4 “definitely disagree”. On half of the items,
endorsement of “definitely agree/slightly agree” is indicative of
ASD-like behavior, whereas on the other half “definitely
disagree/slightly disagree” reveals ASD traits. These latest
scores are reversed. The item scores are summed, to a
maximum score of 10 per subscale and a maximum total score of
50. The other-version omits 10 items as these were labeled
by the developers as being too subjective to be answered by
another person (Baron-Cohen et al. 2001). Higher scores
indicate more severe ASD traits. The Dutch version of the
AQ has good internal consistency, test–retest reliability, and
good discriminative validity
(Hoekstra et al. 2008)
data points (maximum one per subscale) were substituted
with the mean subscale score. The dependent variables are
the total and subscale scores (self-report) and 40-item total
score (self- and other-report).
Interpersonal Reactivity Index (IRI)
The Dutch version of the IRI
(Davis 1980; de Corte et al.
is a widely-used instrument to examine individual
differences in cognitive and emotional attitude towards
2 When designing the study, no other Dutch self-reported measures
for ASD traits or sensory sensitivity were available.
interpersonal situations. This self-report questionnaire
consists of 28 items and four subscales assessing different
aspects of empathy, which is crucial of normal social
functioning, including the maintenance of social relationships
and favoring pro-social behavior (de Corte et al. 2007): (a)
perspective taking, the tendency to adopt another person’s
point of view, (b) fantasy, the tendency to identify with the
feelings and actions of fictitious characters, (c) empathic
concern, the tendency to experience feelings of sympathy
and concern towards others, and (d) personal distress, the
tendency to feel anxious and uneasy in reaction to the
emotions of others
. The first two subscales examine
other-oriented behavior (cognitive component), whereas the
latter two subscales examine self-oriented behavior
(affective component). Each item is rated on a five-point Likert
scale, ranging from 0 “does not describe me well” to 4
“describes me very well”. The item scores are summed to
a maximum of 28 per subscale. While higher
perspectivetaking scores and lower personal distress scores are
associated with better social functioning, correlations between
social functioning and fantasy are low. Empathic concern
is not consistently related to social competence, although
associated with social success characteristics, such as
selflessness and agreeableness. The Dutch version of the IRI
has adequate psychometric properties
(de Corte et al. 2007)
Missing data points (maximum one per subscale) were
substituted with the mean subscale score. The dependent
variables are the subscale scores (self-report) and total score
(self- and other-report).
Sensory Sensitivity Questionnaire (SSQ)
(Minshew and Hobson 2008)
is, after permission
of the authors, translated from English into Dutch
and Geurts 2012)
and back-transformed into English by an
independent native English speaker. The SSQ consists of 13
statements about sensory hyper- or hyposensitivity that can
be endorsed or denied, and assess low pain/temperature (2
items), high pain/temperature (2 items), tactile sensitivity
(3 items), and other sensitivities (6 items). Endorsed items
are summed per subscale and to a total score of maximum
13. Inter-rater reliability is good
(Minshew and Hobson
, but other psychometric properties of the SSQ are yet
unknown. Missing data points for SSQ were not allowed due
to the small number of questionnaire items. The dependent
variable is the total score (self- and other-report).
After explanation of study purposes and procedure,
written informed consent was obtained for all participants. The
AQ, IRI, and SSQ questionnaires were filled out. Additional
questionnaires were filled out and additional measures were
administered in two sessions in a selection of this sample,
but these were described elsewhere
(Lever and Geurts
2016a, b; Lever et al. 2015, 2017)
. The study was approved
by the local institutional ethical review board
(2011-PN1952), and complied with all relevant laws and institutional
First, to compare the ASD and COM group on descriptive
measures, ANOVAs (continuous variables) and Fisher’s test
(categorical variables) were used.
Second, to investigate age-related differences in ASD
symptomatology, two MANCOVAs for AQ and IRI (sub)
scales and an ANCOVA for the SSQ total score3 were run.
Group and sex were the between-subject factors and age and
age2 were included as covariates in a model with main effects
and interactions. Sex was included as between-subject factor
to explore the role of sex. Age and age2 were both centered
to ease interpretation. Separate ANCOVAs on the single
(sub)scales (Bonferroni correction: α = 0.05/6 = 0.0083 for
AQ; α = 0.05/4 = 0.0125 for IRI) were used to follow-up on
the omnibus MANOVA effects. When observing significant
interactions, we ran planned follow-up regressions analyses
(Bonferroni correction: α = 0.05/number of significant
interactions) per group. Third, to examine the relation between
self- and other-report, intra-class correlations coefficients
(ICCs) were calculated with a two-way mixed, absolute
agreement, single-measures effect model
McGraw and Wong 1996; Shrout and Fleiss 1979)
and per group, for total scores of AQ (40 items), IRI (all
items), and SSQ (all items). Levels of agreement were
interpreted as poor (ICC < 0.40), fair (ICC = 0.40–0.59), good
(ICC = 0.60–0.74), and excellent (ICC = 0.75–1.00)
. To further examine the self-other relationship,
we computed three ANOVAs with Group (ASD, COM) as
between-subject factors and Rater (self, other) as
withinsubject factor. Furthermore, to examine whether age-related
differences were also observed by proxies (i.e., other-report),
we ran ANCOVAs for each questionnaire’s total score, with
group and sex as between-subject factors and centered age
and centered age2 as covariates. Additional exploratory
analyses are described in the Online Resources 1, 2, and 3.
All analyses were run with SPSS 22.0
(IBM Corp. 2013)
3 Data of the AQ subscales and SSQ total score were not normally
distributed. However, as (M)ANOVA is thought to be robust against
, we ran parametric tests.
ASD autism spectrum disorder, COM comparison group, M male, F female, PDD-NOS pervasive
developmental disorder not otherwise specified, ISCO International Standard Classification of Occupations,
SCL90 symptom checklist-90, IQ estimated intelligence quotient, ADOS autism diagnostic observation
aMissing: educational level: 3 ASD, 1 COM; occupation: 6 ASD, 11 COM
bUnemployment also included retirement and students
cSCL-90, IQ, and ADOS were assessed in a subgroup of participants (ASD: IQ/ADOS n = 142, SCL-90
n = 172; COM: IQ n = 180, SCL-90 n = 177)
The descriptives of both groups (i.e., sex, age, social
characteristics, years of diagnosis) are depicted in Table 1.4
The age distribution is shown in Fig. 1, AQ total score
4 We cross-checked whether the whole sample differed from the IRI
or SSQ subsample on age, sex, and educational level. The groups did
not significantly differ (all ps > .5).
(79 individuals with ASD between 19 and 40 years
completed the AQ, 79 between 40 and 53 years, and 79
between 53 and 79 years). The groups did not differ in
mean age, but the ASD group was composed of relatively
more males than females as compared to the COM group.
Self-reported questionnaire scores of the ASD and COM
group and subscale comparisons are presented in Table 2.
Follow-up regressions on significant interactions between
age(2) and group are presented in Table 3.
As expected, there was a significant main effect of group
on the AQ (Wilks’ Lambda (Λ) = 0.40, F(5, 423) = 125.60,
p < .001, ηp2 = 0.60), IRI (Λ = 0.72, F(4, 338) = 32.86,
p < .001, ηp2 = 0.28), and SSQ (F(1, 335) = 145.54,
p < .001, ηp2 = 0.31). Adults with ASD reported higher
scores on the SSQ and on all subscales of the AQ than
adults without ASD. On the IRI, ASD adults reported
lower scores on perspective taking and fantasy,
comparable scores on empathic concern, and higher scores on
Self‑Reported ASD Characteristics: Age
There was no significant effect between age or age2 and IRI
scores. In contrast, AQ and SSQ scores were differently
affected by age in the ASD and COM group as showed by
significant interaction effects (AQ: group × age, Λ= 0.97,
F(5, 423) = 3.02, p = .011, ηp2 = 0.04, group × age2,
Λ = 0.96, F(5, 423) = 3.21, p = .007, ηp2 = 0.04; SSQ:
group × age, F(1, 335) = 7.13, p = .008, ηp2 = 0.02,
group × age2, F(1, 335) = 9.02, p = .003, ηp2 = 0.03). In
the ASD group, increasing age was associated with higher
scores on the AQ total score, AQ attention to detail, and
SSQ. However, the effect of age2 indicated a peak of these
traits in middle adulthood (Fig. 1). Furthermore, age was
significantly associated with the AQ social skills subscale,
with increasing age being related to higher scores
without any peak. In the COM group, there was no relation
Significant values after Bonferroni correction (α=0.05/6 = 0.0083 for AQ; α = 0.05/4 = 0.0125 for IRI) are indicated in bold script. Please note
that no Bonferroni correction was needed for SSQ data
ASD autism spectrum disorder, COM comparison group, AQ autism-spectrum quotient, IRI interpersonal reactivity index, SSQ sensory
* p ≤ .05
** p < .01
*** p ≤ .001
between age(2) and any of the self-reported questionnaire
Self‑Reported ASD Characteristics: Sex
Sex differences between the ASD and COM group were
observed as shown by significant interaction effects (AQ:
Λ = 0.97, F(5, 423) = 3.07, p = .010, ηp2 = 0.04; IRI: Λ = 0.97,
F(4, 338) = 2.83, p = .025, ηp2 = 0.03; SSQ: F(1, 335) = 8.01,
p = .005, ηp2 = 0.02). ASD females reported higher scores
than ASD males on the AQ total score (β = 0.19, p = .004),
AQ attention switching subscale (β = 0.19, p = .004), and
SSQ (β = 0.39, p < .001). IRI perspective taking and fantasy
scores did not differ between females and males with ASD
(respectively, β = − 0.11, p = .163 and β = − 0.05, p = .504).
In contrast, non-ASD females reported lower scores than
non-ASD males on the AQ total score (β = − 0.20, p = .006)
and AQ communication subscale (β = − 0.23, p = .001),
Significant values after Bonferroni correction (α= 0.05/5 = 0.01) are indicated in bold script
ASD autism spectrum disorder, COM comparison group, AQ autism-spectrum quotient, SSQ sensory sensitivity questionnaire
* p ≤ .05
** p ≤ .01
*** p ≤ .001
higher scores on the IRI perspective taking and fantasy
subscales (respectively, β = 0.19, p = .010 and β = 0.21,
p = .005), and no differences on the SSQ (β= 0.16, p = .039)
after Bonferroni correction. Females reported higher scores
on the IRI personal distress and empathic concern subscales
than males in both groups (see Table 2).
Differences Between Self‑ and Other‑Reported ASD
The informants were partners (55.0%), family members
(28.4%), friends (11.3%), or others (2.8%), such as
practitioners. Unfortunately, 2.5% did not indicate which type
of relationship they had with the participant. Of two
participants who handed in questionnaires of two different
informants, we included data from one of these (i.e., the
person who has known the participant for the longest time).
The mean length of the relationship between participant
and informant was 24.2 years (SD 13.2; median 24; range
0.5–57.0 years) and comparable between ASD and COM
group (p > .4).
ICCs indicated fair (IRI, SSQ) to excellent (AQ) levels of
agreement between self- and other-report for the total
sample (see Table 4). Levels of agreement were fair for the COM
group and poor to fair in the ASD group.5 Considering the
95% confidence intervals of each group, the levels of
agreement differ between groups on the AQ, but not on the IRI
5 ICCs for the whole group are typically larger than ICCs for
Comparison of self- and other-report revealed a main
effect of rater on the AQ (F(1, 268) = 19.93, p < .001,
ηp2 = 0.07), with lower ratings for self-report than for
otherreport, but no interaction between rater and group (F(1,
268) = 0.36, p = .548, ηp2 = 0.00) (Fig. 2). Hence, the
differences between raters do not seem to be more pronounced in
the ASD group. On the IRI, there was an interaction between
rater and group (F(1, 273) = 4.09, p = .044, ηp2 = 0.02).
Proxies reported lower scores than participants themselves
in both groups, but follow-up comparisons revealed that
this discrepancy was more pronounced in the ASD group
(ASD: F(1, 128) = 24.76, p < .001, ηp2 = 0.16; COM: F(1,
145) = 6.82, p = .010, ηp2 = 0.05). Rater and group also
interacted on SSQ scores (F(1, 132) = 5.98, p = .016, ηp2 = 0.04)
with lower ratings for other-report than for self-report in
the ASD group and vice versa in the COM group.
Followup comparisons revealed that apparent differences were too
small and variability too large to detect significant
differences between self- and other-report in both groups (ASD:
F(1, 61) = 3.27, p = .076, ηp2 = 0.05; COM: F(1, 71) = 2.53,
p = .116, ηp2 = 0.03).6
Group, Age and Sex
Group differences were also revealed by other-reports (all
ps ≤ .009, ηp2 = 0.03–0.52). However, age-related
differences as reported by proxies were not found to be significant
on neither the AQ, IRI, nor SSQ (all ps > .07). Moreover,
proxies reported higher IRI (p < .001, ηp2 = 0.08) and SSQ
scores (p = .005, ηp2 = 0.06) for females than for males, but,
in contrast to the self-reports, similar AQ scores (p = .095,
ηp2 = 0.01). Please note that age- and sex-related findings
were similar in both groups.
6 To check whether the length of the relationship between participant
and informant affected the results, these analyses were rerun with
length of relationship as covariate. It did not alter the pattern of
findings, except that the interaction between rater and group on the IRI
was not significant anymore (p = .079).
To our knowledge, this is the first study focusing on
agerelated differences in self- and other-reported ASD
characteristics in a large sample of intellectually able individuals
with clinical ASD across the adult lifespan including old
age. The findings show clearly that age, sex, and type of
informant are crucial to take into account when studying
ASD characteristics across adulthood.
Self‑Report: Group‑, Sex‑, and Age‑Related
As expected, adults with ASD reported more ASD traits
(e.g., Baron-Cohen et al. 2001; Ruzich et al. 2015)
(Crane et al. 2009; Minshew and Hobson
, and lower perspective taking and fantasy tendencies,
similar empathic concern, and higher personal distress in
reaction to the emotions of others
(Rogers et al. 2007)
individuals without ASD. Moreover, we replicated earlier
findings that females with ASD had more sensory issues
and reported more ASD characteristics than males
et al. 2016; Lai et al. 2011)
, whereas females without ASD
manifested fewer ASD traits than non-ASD males
et al. 2015)
Within the ASD group, age-related differences were
observed in self-reported ASD traits and sensory
sensitivity, with a peak among middle-aged adults. These results are
apparently in contrast with the few cross-sectional studies
investigating the role of age on self-reported ASD symptoms
in (younger) adults as these studies did not find any
association with age
(Bastiaansen et al. 2011; Bishop and Seltzer
2012; Crane et al. 2009; Minshew and Hobson 2008)
found more ASD traits associated with older age (Happé
et al. 2016). However, these studies did not consider a
(Bastiaansen et al. 2011; Bishop and
Seltzer 2012; Crane et al. 2009; Minshew and Hobson 2008)
had a small sample size
(Crane et al. 2009)
or included only
a few individuals aged over 55 (Happé et al. 2016). The high
number of self-reported ASD characteristics in middle
adulthood found in our study and the Happé study, suggests that
ASD characteristics are more heavily experienced in middle
adulthood than in younger or older adults. Not only ASD
characteristics are most pronounced in middle adulthood,
also comorbid psychopathology is frequently experienced
in this life period
(Lever and Geurts 2016b)
adulthood is associated with increased demands of responsibility,
shifting roles, and adjustments to life changes. People may
need to deal with changes in multiple domains, including
psychosocial, emotional, and physical changes (Lachman
2004), that require substantial resources to adequately face
them. These resources could be less efficient in
individuals with ASD, causing distress and highlighting their ASD
traits. Regarding sensory sensitivity, reduced sensory
or better coping mechanisms
in older adulthood may additionally explain the fewer
reported characteristics in old age.
In both adults with and without ASD, empathy, an aspect
of social-emotional reciprocity, was not sensitive to
(e.g., Eysenck et al. 1985)
. It has
previously been demonstrated that age-related differences in
perspective taking and empathic concern may follow an
(O’Brien et al. 2013)
. However, this
pattern was found in a very large sample of more than 75,000
individuals drawn from the general population. Our failure
to replicate this finding is plausibly a power issue as the
directions of estimated coefficients in the current study were
comparable, even though our results fit ASD-related
findings indicating that age did not affect cognitive reasoning on
other persons’ mental states
(Chung et al. 2014)
Within the comparison group, as in previous reports
about the general population, age was not associated with
general ASD symptoms
(Hoekstra et al. 2008; but see;
Broadbent et al. 2013)
or sensory sensitivity
(Crane et al.
2009; Robertson and Simmons 2013)
Self‑ Versus Other‑Report
Overall, the current results show poor to fair agreement
between self- and other-reports of well-known proxies,
even though the agreement of the overall group was
similar to those previously reported for social responsiveness
(De la Marche et al. 2015)
. Given that rather low agreement
7 Given that middle adulthood is also a crucial period for comorbid
psychopathology, we exploratively verified whether the amount of
self-reported psychological distress as measured with the Symptom
(Arrindell and Ettema 2005; Derogatis 1977)
could explain the peak in self-reported ASD characteristics as
measured with the AQ and SSQ. It could not, as the age effects remained
after correcting for SCL-90 scores.
was observed in both the ASD and COM group, it seems
unsuitable to conclude that this is due to poor metacognitive
abilities in ASD, as has been previously argued
Johnson et al. 2009; Kievit and Geurts 2011)
. Rather, a rater
(De Los Reyes 2013; Hirschfeld 1993; John and Robins
1993; Leising et al. 2010)
or a different way of perceiving
or experiencing behavioral traits
(Carlson et al. 2013)
reflect the discrepancy between self- and other-report. For
example, a person may enhance one’s own characteristics
(John and Robins 1993)
or experience his or her so-called
“pathological” traits as more acceptable or desirable than
and, hence, underestimate
the degree of behavioral characteristics relative to others.
Simultaneously, proxies may focus more on the so-called
“pathological” traits than on, what they perceive as,
(Leising et al. 2010)
and, hence, overestimate
certain symptoms. Or, the self may be more accurate about
traits that describe unobservable thoughts and feelings due
to privileged access (e.g. feelings of empathy and sensory
sensitivity), whereas an informant would be more accurate
about observable behavior (e.g., ASD traits)
Also, people can behave differently in different settings, so
certain traits may not be visible to proxies
(De Los Reyes
. To disentangle these different explanations is a
potentially interesting future research avenue. Please note that the
mean difference in AQ score between self and other (i.e.,
1.8) was smaller than in the original Baron-Cohen sample
(i.e., 2.8; 2001), which has been described as good, even
though statistical analyses were lacking.
Regarding the presence of more self-reported ASD traits
by females, which are not reported by proxies, it may
support the idea that females are, in general, better in
camouflaging (i.e., masking or compensating for) their condition
(Dean et al. 2017; Lai et al. 2015, 2016; Rynkiewicz et al.
. This is in line with the finding that females showed
less symptoms than males on a clinician-rated measure
(i.e. the ADOS; Online Resource 3). Alternatively, females
may more strongly perceive their symptoms or, although
speculative, females may feel the need to report more ASD
symptoms in order to be recognized as having ASD, getting
access to the mental health system and receiving
appropriate treatment, as ASD in girls and women is still
underdiagnosed (Halladay et al. 2015). In sum, using self-report to
gain insight into a person’s experience and understanding
of certain feelings, thoughts, and behaviors should also be
considered as a valuable tool for intellectually high
functioning adults with ASD, while discrepancies between
selfand other-report seem to capture different aspects of ASD
Several limitations of this study should be acknowledged.
ADOS and IQ were only assessed within a subgroup of the
clinical sample. However, as demographics and self-reported
scores did not differ between the subgroup and the entire
sample (Online Resource 1), it is expected that the results
extend to the overall ASD sample included in this study. As
such, the sample consisted of intelligent individuals, with
many having a paid job (some high profile), living with a
partner, and being diagnosed with ASD relatively late in
life.8 Therefore, the group is not representative of the entire
autism population and the results cannot be generalized to
the whole spectrum. However, the sample is
representative of those receiving an adulthood diagnoses, which is
a group which has previously been largely ignored within
(but see Geurts and Jansen 2012; Happé
et al. 2016)
, and those typically seen in general adult
mental health care across parts of Europe. Furthermore, recent
reports indicated that a majority of individuals with ASD
may not present intellectual disability
(Brugha et al. 2016;
Christensen et al. 2016)
. As the ADOS was only
administered to individuals with ASD, the information it provided
regarding age, sex, and self- and other-reported
questionnaire associations may be obscured by the lack of
comparison with the control group. Also age, sex, and intelligence
could confound interpretation of the ADOS module 4
(Bastiaansen et al. 2011; Hus and Lord 2014; Pugliese et al.
. Moreover, the cross-sectional nature of the study
does not allow to draw conclusions on how self-reported
ASD characteristics change over the years within-persons.
A longitudinal follow-up is needed to investigate whether
age-related changes in ASD symptoms, generally examined
with measures relying on other information
(i.e., a parent or
caregiver, e.g. Howlin et al. 2013)
, are also detected by ASD
individuals themselves and whether this change trajectory
is indeed one of improvement. Finally, cohort effects could
have occurred as a result of changes in social and cultural
perspectives of ASD. Despite these limitations, to the
current findings do have some potential clinical implications for
this intelligent group of individuals.
The age-related differences observed in self-reported ASD
characteristics suggest that it would be meaningful to inquire
8 We verified whether the time of diagnosis was related to the
amount of self-reported ASD characteristics. AQ total, AQ subscale
and SSQ scores were negatively correlated to time of diagnosis (p’s
between − .147 and − .285, all p’s ≤ .029), but not to IRI scores (all
p’s ≥ .195). However, associations were weak
of diagnosis did not affect the main findings.
after the experience of symptoms at different time-points
within the adult lifespan instead of just assessing this at the
time of diagnosis. Even though such repeated assessment
might be challenging in some countries due to the (lack of)
access to mental health care for ASD adults, it is of
importance that ASD adults get the opportunity to have a regular
checkup in order to provide individually tailored care which
is age-appropriate. Moreover, the self-reported sex
differences on ASD traits and sensory sensitivities underline that
clinical professionals should be aware of symptomatic
differences between males and females. Finally, our findings also
suggest that it is important to rely on more than one source
for diagnostic assessment
(National Institute for Health and
Clinical Excellence 2012; Trimbos 2013)
. Whether the other
informant is a partner, family member, or friend may yield
subtle differences in the amount of reported ASD
characteristics. While friends reported less ASD traits and more
empathy compared to partners, discrepancies between
selfand other-report were the smallest for partners on the AQ,
for friends on the IRI, and for family members on the SSQ
(Online Resource 2). Associations between a clinician-rated
measure of ASD symptomatology (i.e., the ADOS) and
selfand other-reported questionnaires on ASD characteristics
were also very weak (Online Resource 3). In general, as
clients and proxies seem to perceive different aspects of ASD
symptomatology, the discrepancies may provide an
interesting contrast to discuss during assessment.
In this large cross-sectional study of adults with clinical
diagnoses of ASD, we demonstrated that adults with ASD
experience a significant degree of ASD characteristics,
empathic difficulties, and sensory sensitivities across
adulthood. However, in line with the suggestion that ASD
characteristics may fluctuate over the lifespan, age-related
differences in ASD traits and sensory sensitivities were observed.
Self-reported ASD traits and sensory sensitivities are highest
in middle adulthood, and lower in young and older
adulthood. Nevertheless, these age-related differences were not
reported by proxies who have known the participants for a
long time. Self and proxies may grasp distinct aspects of
symptomatology. Longitudinal follow-up studies should
reveal whether self-reported ASD symptoms are experienced
to change over time.
Acknowledgments We wish to express our gratitude to all participants
and their proxies for their dedicated time, to the mental health care
institutions and client organizations (Dr. Leo Kannerhuis, GGZ
NoordHolland-Noord, GGZ Breburg, NVA, PAS) for their help with
participant recruitment, to our research assistants (Nynke Dicke, Barbara van
Heijst) for their assistance with data collection, to Nancy Minshew and
Jessica Hobson for their permission to translate the SSQ, and to Mike
Cohen for back-translating the Dutch SSQ.
Author Contributions AGL participated in the design, execution and
coordination of the study, performed measurements and the statistical
analysis and interpretation of the data, and drafted the manuscript;
HMG supervised the study, participated in the design, the set-up of
the statistical plan and interpretation of the data, and helped to draft
the manuscript. Both authors read and approved the final manuscript.
Funding This study was funded by Innovational Research
Incentives Scheme Vidi (NWO-MagW) awarded to HMG (Grant Number
Compliance with Ethical Standards
Conflict of interest The authors declare that they have no conflict of
Ethical Approval All procedures performed in studies involving human
participants were in accordance with the ethical standards of the
institutional and/or national research committee and with the 1964 Helsinki
declaration and its later amendments or comparable ethical standards.
Informed Consent Informed consent was obtained from all individual
participants included in the study.
Open Access This article is distributed under the terms of the Creative
Commons Attribution 4.0 International License
(http://creativecommons.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.
Achenbach , T. M. , Krukowski , R. A. , Dumenci , L. , & Ivanova , M. Y. ( 2005 ). Assessment of adult psychopathology: Meta-analyses and implications of cross-informant correlations . Psychological Bulletin , 131 ( 3 ), 361 - 382 .
American Psychiatric Association. ( 2000 ). Diagnostic and statistical manual of mental disorders (4th ed ., text rev.) . Washington, DC: American Psychiatric Association.
American Psychiatric Association. ( 2013 ). The diagnostic and statistical manual of mental disorders (5th ed .). Washington, DC: American Psychiatric Association.
Arrindell , W. A. , & Ettema , J. H. M. ( 2005 ). SCL- 90 . Handleiding bij een multidimensionale psychopathologie-indicator [SCL-90: Manual for a multidimensional indicator of psychopathology] . Amsterdam: Pearson.
Baron-Cohen , S. , Cassidy , S. , Auyeung , B. , Allison , C. , Achoukhi , M. , Robertson , S. , …, & Lai , M. C. ( 2014 ). Attenuation of typical sex differences in 800 adults with autism vs. 3,900 controls . PloS one , 9 ( 7 ), e102251 .
Baron-Cohen , S. , Wheelwright , S. , Skinner , R. , Martin , J. , & Clubley , E. ( 2001 ). The autism-spectrum quotient (AQ): Evidence from Asperger syndrome/high-functioning autism, males and females, scientists and mathematicians . Journal of Autism and Developmental Disorders , 31 ( 1 ), 5 - 17 .
Bastiaansen , J. A. , Meffert , H. , Hein , S. , Huizinga , P. , Ketelaars , C. , Pijnenborg , M. , …, & de Bildt , A. ( 2011 ). Diagnosing autism spectrum disorders in adults: The use of autism diagnostic observation schedule (ADOS) module 4 . Journal of Autism and Developmental Disorders , 41 ( 9 ), 1256 - 1266 .
Bastiaansen , J. A. , Thioux , M. , Nanetti , L., van der Gaag , C. , Ketelaars , C. , Minderaa , R. , & Keysers , C. ( 2011 ). Age-related increase in inferior frontal gyrus activity and social functioning in autism spectrum disorder . Biological Psychiatry , 69 ( 9 ), 832 - 838 .
Bishop , S. L. , & Seltzer , M. M. ( 2012 ). Self-reported autism symptoms in adults with autism spectrum disorders . Journal of Autism and Developmental Disorders , 42 ( 11 ), 2354 - 2363 .
Broadbent , J. , Galic , I. , & Stokes , M. A. ( 2013 ). Validation of autism spectrum quotient adult version in an Australian sample . Autism Research and Treatment , 2013 , 984205 .
Brugha , T. S. , Spiers , N. , Bankart , J. , Cooper , S. A. , McManus , S. , Scott , F. J. , …, & Tyrer , F. ( 2016 ). Epidemiology of autism in adults across age groups and ability levels . The British Journal of Psychiatry , 209 ( 6 ), 498 - 503 .
Carlson , E. N. , Vazire , S. , & Oltmanns , T. F. ( 2013 ). Self-other knowledge asymmetries in personality pathology . Journal of Personality , 81 ( 2 ), 155 - 170 .
Christensen , D. L. , Bilder , D. A. , Zahorodny , W. , Pettygrove , S. , Durkin , M. S. , Fitzgerald , R. T., …, & Yeargin-Allsopp , M. ( 2016 ). Prevalence and characteristics of autism spectrum disorder among 4-year-old children in the autism and developmental disabilities monitoring network . Journal of Developmental & Behavioral Pediatrics , 37 ( 1 ), 1 - 8 .
Chung , Y. S. , Barch , D. , & Strube , M. ( 2014 ). A meta-analysis of mentalizing impairments in adults with schizophrenia and autism spectrum disorder . Schizophrenia Bulletin , 40 ( 3 ), 602 - 616 .
Cicchetti , D. V. ( 1994 ). Guidelines, criteria, and rules of thumb for evaluating normed and standardized assessment instruments in psychology . Psychological Assessment , 6 ( 4 ), 284 .
Cohen , J. ( 1988 ). Statistical power analysis for the behavioral sciences (2nd ed .). Hillsdale, NJ: Erlbaum.
Crane , L. , Goddard , L. , & Pring , L. ( 2009 ). Sensory processing in adults with autism spectrum disorders . Autism , 13 ( 3 ), 215 - 228 .
Davis , M. H. ( 1980 ). A multidimensional approach to individual differences in empathy . JSAS Catalog of Selected Documents in Psychology , 10 , 85 - 104 .
Davis , M. H. ( 1983 ). Measuring individual differences in empathy: Evidence for a multidimensional approach . Journal of Personality and Social Psychology , 44 ( 1 ), 113 - 126 .
de Bildt , A. , & de Jonge, M. V. ( 2008 ). Autisme diagnostisch observatie schema . Amsterdam: Hogrefe.
de Corte , K. , Buysse , A. , Verhofstadt , L. L. , Roeyers , H. , Ponnet , K. , & Davis , M. H. ( 2007 ). Measuring empathic tendencies: Reliability and validity of the Dutch version of the interpersonal reactivity index . Psychologica Belgica , 47 ( 4 ), 235 - 260 .
De la Marche , W. , Noens , I. , Kuppens , S. , Spilt , J. L. , Boets , B. , & Steyaert , J. ( 2015 ). Measuring quantitative autism traits in families: Informant effect or intergenerational transmission? European Child & Adolescent Psychiatry , 24 ( 4 ), 385 - 395 .
De Los Reyes , A. ( 2013 ). Strategic objectives for improving understanding of informant discrepancies in developmental psychopathology research . Development and Psychopathology , 25 ( 3 ), 669 - 682 .
Dean , M. , Harwood , R. , & Kasari , C. ( 2017 ). The art of camouflage: Gender differences in the social behaviors of girls and boys with autism spectrum disorder . Autism , 21 ( 6 ), 678 - 689 .
Derogatis , L. R. ( 1977 ). Administration, scoring, and procedures manual for the SCL- 90 -R. Baltimore , MD: Clinical Psychometrics Research.
Esbensen , A. J. , Seltzer , M. M. , Lam , K. S. , & Bodfish , J. W. ( 2009 ). Age-related differences in restricted repetitive behaviors in autism spectrum disorders . Journal of Autism and Developmental Disorders , 39 ( 1 ), 57 - 66 .
Eysenck , S. B. , Pearson , P. R. , Easting , G. , & Allsopp , J. F. ( 1985 ). Age norms for impulsiveness, venturesomeness and empathy in adults . Personality and Individual Differences , 6 ( 5 ), 613 - 619 .
Fozard , J. L. ( 1990 ). Vision and hearing in aging . In J. E. Birren & K. W. Schaie (Eds.), Handbook of the psychology of aging (3rd ed ., pp. 143 - 156 ). San Diego, CA: Academic Press.
Frith , U. ( 2004 ). Confusions and controversies about Asperger syndrome . Journal of Child Psychology and Psychiatry , 45 ( 4 ), 672 - 686 .
Geurts , H. M. , & Jansen , M. D. ( 2012 ). A retrospective chart study: The pathway to a diagnosis for adults referred for ASD assessment . Autism , 16 ( 3 ), 299 - 305 .
Grandin , T. ( 2011 ). The way I see it: A personal look at autism & Asperger's . Arlington, TX: Future Horizons.
Halladay , A. K. , Bishop , S. , Constantino , J. N. , Daniels , A. M. , Koenig , K. , Palmer , K. , …, & Szatmari , P. ( 2015 ). Sex and gender differences in autism spectrum disorder: Summarizing evidence gaps and identifying emerging areas of priority . Molecular Autism . https://doi.org/10.1186/s13229-015-0019-y.
Hallgren , K. A. ( 2012 ). Computing inter-rater reliability for observational data: An overview and tutorial . Tutorials in Quantitative Methods for Psychology , 8 ( 1 ), 23 - 34 .
Happé , F. G. , Mansour , H. , Barrett , P. , Brown , T., Abbott , P. , & Charlton , R. A. ( 2016 ). Demographic and cognitive profile of individuals seeking a diagnosis of autism spectrum disorder in adulthood . Journal of Autism and Developmental Disorders , 46 ( 11 ), 3469 - 3480 .
Happé , F. G. E. , & Charlton , R. A. ( 2012 ). Aging in autism spectrum disorders: A mini-review . Gerontology , 58 ( 1 ), 70 - 78 .
Hategan , A. , Bourgeois , J. A. , & Goldberg , J. ( 2016 ). Aging with autism spectrum disorder: An emerging public health problem . International Psychogeriatrics , 29 ( 4 ), 695 - 697 .
Helles , A. , Gillberg , I. C. , Gillberg , C. , & Billstedt , E. ( 2016 ). Asperger syndrome in males over two decades: Quality of life in relation to diagnostic stability and psychiatric comorbidity . Autism . https:// doi.org/10.1177/1362361316650090.
Hirschfeld , R. M. ( 1993 ). Personality disorders: Definition and diagnosis . Journal of Personality Disorders , 7 ( Suppl . 1), 9 - 17 .
Hoekstra , R. A. , Bartels , M. , Cath , D. C. , & Boomsma , D. I. ( 2008 ). Factor structure, reliability and criterion validity of the autismspectrum quotient (AQ): A study in Dutch population and patient groups . Journal of Autism and Developmental Disorders , 38 ( 8 ), 1555 - 1566 .
Howlin , P. , Moss , P. , Savage , S. , & Rutter , M. ( 2013 ). Social outcomes in mid-to later adulthood among individuals diagnosed with autism and average nonverbal IQ as children . Journal of the American Academy of Child & Adolescent Psychiatry , 52 ( 6 ), 572 - 581 .
Hull , L. , Mandy , W. , & Petrides , K. V. ( 2017 ). Behavioural and cognitive sex/gender differences in autism spectrum condition and typically developing males and females . Autism , 21 ( 6 ), 706 - 727 . https://doi.org/10.1177/1362361316669087.
Hus , V. , & Lord , C. ( 2014 ). The autism diagnostic observation schedule, module 4: Revised algorithm and standardized severity scores . Journal of Autism and Developmental Disorders , 44 ( 8 ), 1996 - 2012 .
IBM Corp. ( 2013 ). IBM SPSS statistics for Windows (Version 22 .0 ed.). Armonk, NY: IBM Corp.
John , O. P. , & Robins , R. W. ( 1993 ). Determinants of interjudge agreement on personality traits: The big five domains, observability, evaluativeness, and the unique perspective of the self . Journal of Personality , 61 ( 4 ), 521 - 551 .
Johnson , S. A. , Filliter , J. H. , & Murphy , R. R. ( 2009 ). Discrepancies between self-and parent-perceptions of autistic traits and empathy in high functioning children and adolescents on the autism spectrum . Journal of Autism and Developmental Disorders , 39 ( 12 ), 1706 - 1714 .
Jones , A. P. , Happé , F. G. , Gilbert , F. , Burnett , S. , & Viding , E. ( 2010 ). Feeling, caring, knowing: Different types of empathy deficit in boys with psychopathic tendencies and autism spectrum disorder . Journal of Child Psychology and Psychiatry , 51 ( 11 ), 1188 - 1197 .
Kern , J. K. , Trivedi , M. H. , Garver , C. R. , Grannemann , B. D. , Andrews , A. A. , Savla , J. S. , …, & Schroeder , J. L. ( 2006 ). The pattern of sensory processing abnormalities in autism . Autism , 10 ( 5 ), 480 - 494 .
Kievit , R. A. , & Geurts , H. M. ( 2011 ). Autism and perception of awareness in self and others: Two sides of the same coin or dissociated abilities? Cognitive Neuroscience , 2 ( 2 ), 119 - 120 .
Kooij , S. J. J. , Boonstra , M. A. , Swinkels , S. H. N. , Bekker , E. M. , de Noord , I. , & Buitelaar , J. K. ( 2008 ). Reliability, validity, and utility of instruments for self-report and informant report concerning symptoms of ADHD in adult patients . Journal of Attention Disorders , 11 ( 4 ), 445 - 458 .
Lachman , M. E. ( 2004 ). Development in midlife . Annual Review of Psychology , 55 , 305 - 331 .
Lai , M. C. , Lombardo , M. V. , Auyeung , B. , Chakrabarti , B. , & BaronCohen , S. ( 2015 ). Sex/gender differences and autism: Setting the scene for future research . Journal of the American Academy of Child & Adolescent Psychiatry , 54 ( 1 ), 11 - 24 .
Lai , M. C. , Lombardo , M. V. , Pasco , G. , Ruigrok , A. N. , Wheelwright , S. J. , Sadek , S. A. , …, & Baron-Cohen , S. ( 2011 ). A behavioral comparison of male and female adults with high functioning autism spectrum conditions . PLoS ONE , 6 ( 6 ), e20835 . https://doi. org/10.1371/journal.pone. 0020835 .
Lai , M. C. , Lombardo , M. V. , Ruigrok , A. N. , Chakrabarti , B. , Auyeung , B. , Szatmari , P. , …, & Baron-Cohen , S. ( 2016 ). Quantifying and exploring camouflaging in men and women with autism . Autism . https://doi.org/10.1177/1362361316671012.
Leising , D. , Erbs , J. , & Fritz , U. ( 2010 ). The letter of recommendation effect in informant ratings of personality . Journal of Personality and Social Psychology , 98 ( 4 ), 668 - 682 .
Lever , A. G. , & Geurts , H. M. ( 2012 ). Vragenlijst voor sensorische gevoeligheid [sensory sensitivity questionnaire] . Amsterdam: University of Amsterdam.
Lever , A. G. , & Geurts , H. M. ( 2016a ). Age-related differences in cognition across the adult lifespan in autism spectrum disorder . Autism Research , 9 ( 6 ), 666 - 676 . https://doi.org/10.1002/aur.1545.
Lever , A. G. , & Geurts , H. M. ( 2016b ). Psychiatric co-occurring symptoms and disorders in young, middle-aged, and older adults with autism spectrum disorder . Journal of Autism and Developmental Disorders , 46 ( 6 ), 1916 - 1930 .
Lever , A. G. , Ridderinkhof , K. R. , Marsman , M. , & Geurts , H. M. ( 2017 ). Reactive and proactive interference control in adults with autism spectrum disorder across the lifespan . Developmental Psychology , 53 ( 2 ), 379 - 395 .
Lever , A. G. , Werkle-Bergner , M. , Brandmaier , A. M. , Ridderinkhof , K. R. , & Geurts , H. M. ( 2015 ). Atypical working memory decline across the adult lifespan in autism spectrum disorder ? Journal of Abnormal Psychology , 124 ( 4 ), 1014 - 1026 .
Lord , C. , Risi , S. , Lambrecht , L. , Cook , E. H. Jr. , Leventhal , B. L. , DiLavore , P. C., …, & Rutter , M. ( 2000 ). The autism diagnostic observation schedule-generic: A standard measure of social and communication deficits associated with the spectrum of autism . Journal of Autism and Developmental Disorders , 30 ( 3 ), 205 - 223 .
Louwerse , A. , Eussen , M. L. J. M. , Van der Ende , J., de Nijs, P. F. A. , Van Gool , A. R. , Dekker , L. P. , …, & Greaves-Lord , K. ( 2015 ). ASD symptom severity in adolescence of individuals diagnosed with PDD-NOS in childhood: Stability and the relation with psychiatric comorbidity and societal participation . Journal of Autism and Developmental Disorders , 45 ( 12 ), 3908 - 3918 .
Magiati , I. , Tay , X. W. , & Howlin , P. ( 2014 ). Cognitive, language, social and behavioural outcomes in adults with autism spectrum disorders: A systematic review of longitudinal follow-up studies in adulthood . Clinical Psychology Review , 34 ( 1 ), 73 - 86 .
McGraw , K. O. , & Wong , S. P. ( 1996 ). Forming inferences about some intraclass correlation coefficients . Psychological Methods , 1 ( 1 ), 30 - 46 .
Minshew , N. J. , & Hobson , J. A. ( 2008 ). Sensory sensitivities and performance on sensory perceptual tasks in high-functioning individuals with autism . Journal of Autism and Developmental Disorders , 38 ( 8 ), 1485 - 1498 .
Möricke , E. , Buitelaar , J. K. , & Rommelse , N. N. ( 2016 ). Do we need multiple informants when assessing autistic traits? The degree of report bias on offspring, self, and spouse ratings . Journal of Autism and Developmental Disorders , 46 ( 1 ), 164 - 175 .
National Institute for Health and Clinical Excellence . ( 2012 ). Autism: Recognition, referral, diagnosis and management of adults on the autism spectrum . Retrieved from http://guidance.nice.org.uk/ CG142.
Noens , I. , De la Marche , W. , & Scholte , E. ( 2012 ). SRS-A-Screeningslijst voor autismespectrumstoornissen: Handleiding . Amsterdam: Hogrefe.
O'Brien , E. , Konrath , S. H. , Gruhn , D. , & Hagen , A. L. ( 2013 ). Empathic concern and perspective taking: Linear and quadratic effects of age across the adult life span . The Journals of Gerontology , Series B, 68 ( 2 ), 168 - 175 .
Perkins , E. A. , & Berkman , K. A. ( 2012 ). Into the unknown: Aging with autism spectrum disorders . American Journal on Intellectual and Developmental Disabilities , 117 ( 6 ), 478 - 496 .
Piven , J. , Harper , J. , Palmer , P. , & Arndt , S. ( 1996 ). Course of behavioral change in autism: A retrospective study of high-IQ adolescents and adults . Journal of the American Academy of Child & Adolescent Psychiatry , 35 ( 4 ), 523 - 529 .
Piven , J. , & Rabins , P. ( 2011 ). Autism spectrum disorders in older adults: Toward defining a research agenda . Journal of the American Geriatrics Society , 59 ( 11 ), 2151 - 2155 .
Pugliese , C. E. , Kenworthy , L. , Bal , V. H. , Wallace , G. L. , Yerys , B. E. , Maddox , B. B. , …, & Herrington , J. D. ( 2015 ). Replication and comparison of the newly proposed ADOS-2, module 4 algorithm in ASD without ID: A multi-site study . Journal of Autism and Developmental Disorders , 45 ( 12 ), 3919 - 3931 .
Robertson , A. E. , & Simmons , D. R. ( 2013 ). The relationship between sensory sensitivity and autistic traits in the general population . Journal of Autism and Developmental Disorders , 43 ( 4 ), 775 - 784 .
Rogers , K. , Dziobek , I. , Hassenstab , J. , Wolf , O. T. , & Convit , A. ( 2007 ). Who cares? revisiting empathy in Asperger syndrome . Journal of Autism and Developmental Disorders , 37 ( 4 ), 709 - 715 .
Ruzich , E. , Allison , C. , Smith , P. , Watson , P. , Auyeung , B. , Ring , H. , & Baron-Cohen , S. ( 2015 ). Measuring autistic traits in the general population: A systematic review of the autism-spectrum Quotient (AQ) in a nonclinical population sample of 6,900 typical adult males and females . Molecular Autism . https://doi. org/10.1186/2040-2392-6-2.
Rynkiewicz , A. , Schuller , B. , Marchi , E. , Piana , S. , Camurri , A. , Lassalle , A. , & Baron-Cohen , S. ( 2016 ). An investigation of the 'female camouflage effect'in autism using a computerized ADOS-2 and a test of sex/gender differences . Molecular Autism . https://doi.org/10.1186/s13229-016-0073-0.
Samuel , D. B. , Suzuki , T. , & Griffin , S. A. ( 2016 ). Clinicians and clients disagree: Five implications for clinical science . Journal of Abnormal Psychology , 125 ( 7 ), 1001 - 1010 .
Seltzer , M. M. , Shattuck , P. , Abbeduto , L. , & Greenberg , J. S. ( 2004 ). Trajectory of development in adolescents and adults with autism . Mental Retardation and Developmental Disabilities Research Reviews , 10 ( 4 ), 234 - 247 .
Shattuck , P. T. , Seltzer , M. M. , Greenberg , J. S. , Orsmond , G. I. , Bolt , D. , Kring , S. , …, & Lord , C. ( 2007 ). Change in autism symptoms and maladaptive behaviors in adolescents and adults with an autism spectrum disorder . Journal of Autism and Developmental Disorders , 37 ( 9 ), 1735 - 1747 .
Shrout , P. E. , & Fleiss , J. L. ( 1979 ). Intraclass correlations: Uses in assessing rater reliability . Psychological Bulletin , 86 ( 2 ), 420 - 428 .
Stevens , J. P. ( 2009 ). Applied multivariate statistics for the social sciences . New York: Routledge.
Trimbos. ( 2013 ). Multidisciplinaire richtlijn diagnostiek en behandeling van autismespectrumstoornissen bij volwassenen . Utrecht: De Tijdstroom.
Uterwijk , J. ( 2000 ). WAIS-III Nederlandstalige bewerking . Technische handleiding. Lisse , The Netherlands: Swets & Zeitlinger.
van der Ende , J., Verhulst , F. C. , & Tiemeier , H. ( 2012 ). Agreement of informants on emotional and behavioral problems from childhood to adulthood . Psychological Assessment , 24 ( 2 ), 293 - 300 .
van Wijngaarden-Cremers , P. J. M. , van Eeten , E. , Groen , W. B., van Deurzen, P. A. , Oosterling , I. J. , & van der Gaag , R. J. ( 2014 ). Gender and age differences in the core triad of impairments in autism spectrum disorders: A systematic review and meta-analysis . Journal of Autism and Developmental Disorders , 44 ( 3 ), 627 - 635 .
Vazire , S. ( 2010 ). Who knows what about a person? The self-other knowledge asymmetry (SOKA) model . Journal of Personality and Social Psychology , 98 ( 2 ), 281 - 300 .
Wechsler , D. ( 1997 ). Wechsler adult intelligence scale (WAIS-III) . San Antonio, TX: Psychological Corporation.
Woodbury-Smith , M. , Robinson , J. , Wheelwright , S. , & Baron-Cohen , S. ( 2005 ). Screening adults for asperger syndrome using the AQ: A preliminary study of its diagnostic validity in clinical practice . Journal of Autism and Developmental Disorders , 35 ( 3 ), 331 - 335 .
Wright , S. D. , Brooks , D. E. , & Grandin , T. ( 2013 ). The challenge and promise of autism spectrum disorders in adulthood and aging: A systematic review of the literature ( 1990 - 2013 ). Autism Insights , 5 , 21 - 73 . https://doi.org/10.4137/AUI.S11072.
Wright , S. D. , Wright , C. A. , D'Astous , V. , & Wadsworth , A. M. ( 2016 ). Autism aging . Gerontology & Geriatrics Education . https://doi.org/10.1080/02701960. 2016 . 1247073 .