Smithetal.2012.pdf

NEW RESEARCH

Developmental Trajectories in
Adolescents and Adults With Autism:

The Case of Daily Living Skills
Leann E. Smith, Ph.D., Matthew J. Maenner, Ph.D., Marsha Mailick Seltzer, Ph.D.

Objective: This study aimed to investigate the longitudinal course of daily living skills in a
large, community-based sample of adolescents and adults with autism spectrum disorders
(ASD) over a 10-year period. Method: Adolescents and adults with ASD (n � 397) were
drawn from an ongoing, longitudinal study of individuals with ASD and their families. A
comparison group of 167 individuals with Down syndrome (DS) were drawn from a linked
longitudinal study. The Waisman Activities of Daily Living Scale was administered four times
over a 10-year period. Results: We used latent growth curve modeling to examine change in
daily living skills. Daily living skills improved for the individuals with ASD during
adolescence and their early 20s, but plateaued during their late 20s. Having an intellectual
disability was associated with lower initial levels of daily living skills and a slower change over
time. Individuals with DS likewise gained daily living skills over time, but there was no
significant curvature in the change. Conclusions: Future research should explore what
environmental factors and interventions may be associated with continued gains in daily
living skills for adults with ASD. J. Am. Acad. Child Adolesc. Psychiatry, 2012;51(6):
622– 631. Key Words: daily living skills, autism, adolescence, adulthood, trajectories
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A utism spectrum disorders (ASDs) are life-long developmental disabilities that af-fect an estimated 1 in 110 children in the
United States.1 ASDs are characterized by im-
pairments in communication and social interac-
tion as well as the presence of repetitive behav-
iors. In recent years, increasing attention has
been given to understanding the behavioral phe-
notype of ASD during adolescence and adult-
hood. For instance, researchers have explored
how autism symptoms and behavior problems
change across adolescence and adulthood.2-4

Other work has focused on measuring educa-
tional and occupational outcomes for adults with
ASD, with results indicating that few individuals
reach high levels of independence.5,6 Virtually no
studies, however, have explored the develop-
ment of independence in daily living skills in
adolescents and adults with ASD, even though
such abilities are often cited as important factors

An interview with the author is available by podcast at
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for successful outcomes for adults with intellec-
tual and developmental disabilities (IDD).7,8 The

resent study addressed this gap by examining
rajectories of daily living skills over a 10-year
eriod in a large, community sample of adoles-
ents and adults with ASD.

aily Living Skills in Individuals With ASD
aily living skills constitute a critical domain of

daptive behaviors, which are defined as behav-
ors necessary for age-appropriate, independent
unctioning in social, communication, daily liv-
ng, or motor areas. Past research suggests that
he development of daily living skills may be
articularly challenging for individuals with
SD. Children with autism often have significant

mpairments in daily living skills compared with
ell-matched controls,9,10 and as early as 36

months of age such children display a greater
discrepancy between their adaptive behavior and
mental age than children with other develop-
mental delays.11 These delays in daily living
kills may become more pronounced over time.

n a validation study of the Vineland Adaptive

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DEVELOPMENTAL TRAJECTORIES AND AUTISM

Downloa
Behavior Scales’ supplemental norms for autism,
younger children with ASD had higher standard
scores than older children with ASD in all adap-
tive behavior domains, including daily living
skills, suggesting that as children with ASD
grow, they increasingly lag behind their same-
age peers.12 Similarly, in sample of 1,089 children
and adolescents with ASD, Kanne et al.13 recently
found that adolescents had a greater gap be-
tween their mental age and adaptive skills than
younger children, suggesting that individuals
with ASD may gain daily living skills at a pace
slower than the rate of their intellectual growth.
These cross-sectional findings highlight the need
for longitudinal studies to elucidate how daily
living skills change over time for individuals
with ASD and what factors are associated with
improvements in these skills.

Most studies that have examined within-person
change in daily living skills for individuals with
autism notably have focused on early childhood.
For instance, Freeman et al.14 explored change in
the Vineland Adaptive Behavior Scales in chil-
dren with ASD and found that daily living skills
improved with age. In addition, results indicated
that children with IQs at or above 70 improved at
a faster rate than children whose IQs were below
70.14 Similarly, in a longitudinal study of daily
living skills in preschoolers with ASD, Green and
Carter15 found a linear increase in daily living
skills over a 3-year period, with lower IQ scores
and higher levels of autism symptoms associated
with slower gains. In a recent study of children
with high-functioning autism, daily living skills
improved over time, although the rate of change
slowed as children entered adolescence.16 Taken
together, these studies suggest that daily living
skills improve during early childhood and into
adolescence, although the rate of change slows
over time, and that the presence of an intellectual
disability (ID) further slows the rate of growth.
Questions remain, however, regarding whether
daily living skills continue to improve through ado-
lescence and adulthood and the extent to which ID
may influence these later-life trajectories.

The literature on daily living skills for adults
with other types of IDD may offer insights into
possible patterns of change in daily living skills
for those with ASD. For example, Esbensen et
al.17 explored functional abilities (housekeeping,
personal care, meal-related activities, and mobil-
ity domains) over a nine-year period in a sample

of individuals with IDD, including a large sub-

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sample of individuals with Down syndrome
(DS). Results indicated that housekeeping skills
improved over time, whereas personal care and
mobility skills declined over the same period.
Improvements in housekeeping skills were fast-
est for younger individuals and declines in per-
sonal care skills were fastest for older individu-
als.17 However, this study did not examine the

ossibility of curvilinear change. It may be that
aily living skills improve for individuals with

DD during adolescence and early adulthood but
ecline later in adulthood. The present study
xamined this hypothesis by using latent growth
urve modeling to test for linear and curvilinear
hange in daily living skills for adolescents and
dults with ASD as well as for similarly aged
ndividuals with DS.

resent Study
he primary aim of the present study was to

nvestigate the longitudinal course of daily living
kills in a large, community sample of adoles-
ents and adults with ASD. Daily living skills
ere measured on four occasions over a 10-year
eriod, allowing for an examination of linear and
urvilinear change. Furthermore, due to the wide
ange of ages of participants in our study (10 –52
ears at Time 1), we were able to explore the
ffects of the age of the individual with ASD
termed “child age”) in addition to ID status on
nitial level of daily living skills as well as change
n daily living skills over time. Residential status
f the individual with ASD (living with parent
s. not living with parent) also was examined as
time-varying covariate. To provide a bench-
ark for interpreting trends among the adoles-

ents and adults with ASD, a secondary aim of
he present study was to examine change in daily
iving skills among similarly aged individuals

ith DS, again measured on four occasions over
10-year period. Although we did not conduct a
irect comparison given differences in the age
etween samples, we explored change in the DS
ample to provide additional context for inter-
reting scores in the ASD group.

Based on past studies documenting that au-
ism symptoms and behavior problems tend to
ecome less severe during adolescence and
dulthood,2 we hypothesized that there would
e concomitant improvements in daily living
kills over the course of the study. However,
ased on recent work by Taylor and Seltzer3
indicating that the rate of improvement in autism

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SMITH et al.
symptoms and behavior problems slows after
entering adulthood, we also hypothesized that
the change in daily living skills would be curvi-
linear; that is, that the rate of change would
decrease over time. Next, consistent with past
studies showing that daily living skills improve
with age for children with ASD,14,15 we hypoth-
esized that there would be a significant associa-
tion between age and initial level of daily living
skills. Given the association between intelligence
and daily living skills in other samples,10,13,18 we
hypothesized that having an ID would be associ-
ated with a lower initial level of daily living skills.
Based on the association between ID and growth in
daily living skills in studies of younger children
with ASD,14,15 we hypothesized that having an ID
would be associated with slower change in daily
living skills for adolescents and adults with ASD.

Regarding our secondary aim, based on past
work showing gains over time in functional
abilities for individuals with ID,17 we hypothe-
sized that there would be improvements in daily
living skills for individuals with DS. We also
hypothesized that individuals with DS would dis-
play curvilinear change, or a slowing of improve-
ment, consistent with findings that individuals
with DS are at risk for dementia as they age.19,20

METHOD
Autism Sample Participants
Participants were drawn an ongoing, multi-wave, lon-
gitudinal study of 406 individuals with ASD and their
families, the Adolescents and Adults with Autism
study (AAA).21 The present study focused on four of
eight points of data collection, Times 1, 4, 7, and 8.
Families were recruited via agencies, schools, diagnos-
tic clinics, and media announcements. At entry into the
AAA study, families met three criteria: the family
included a child 10 years of age or older; the child had
received a diagnosis of ASD from a medical, psycho-
logical, or educational professional; and scores on the
Autism Diagnostic Interview—Revised (ADI-R)22

were consistent with the parental report of an ASD.
Of the original sample of 406 individuals, nine

were excluded from the present study, as they did
not have complete data on activities of daily living at
Time 1. Excluded cases were not significantly differ-
ent from the full sample in child age, sex, family
income, or parental education. The individuals with
ASD in the present study ranged from 10 to 52 years
of age at the beginning of the study (Time 1: mean �
21.84 years, SD � 9.32 years; Time 4: mean � 26.25 years,
SD � 9.36 years; Time 7: mean � 29.87 years, SD � 9.19

years; and Time 8: mean � 31.23 years, SD � 9.02). The

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ajority of the sample was male (73%) and 70% of the
ample had a comorbid diagnosis of ID.

When the AAA study began in 1998, 65% of the
ndividuals with ASD lived with their families and
5% lived away from home. An increasing proportion
f individuals moved away from the family home at
ach subsequent point of data collection, such that at
imes 4, 7, and 8, 56%, 45%, and 47% were co-residing
ith their families, respectively. About half (52.2%) of
arent respondents had at least a bachelor’s degree,
nd the median annual household income was $50,000
o $59,000 in 1998 to 1999. The majority of participants
93%) were white. Most respondents were mothers
96.5%), with 14 fathers participating (3.5%).

There were no significant differences between fami-
ies who participated in all waves of data collection and
amilies with missing data in child sex or ID status.
owever, consistent with age-related morbidity and
ortality, families of older individuals were more likely

o end study participation than were their younger
ounterparts (F � 3.78, p � .05). Importantly, there were

no significant associations between complete study par-
ticipation and daily living skill scores at Time 1.

Down Syndrome Sample Participants
To benchmark changes in daily living skills in individ-
uals with ASD, a sample of individuals with DS was
drawn from a linked longitudinal study of 461 indi-
viduals with ID.23 Families were included in the study
f they met two criteria: the mother was between 55
nd 85 years of age and the son or daughter lived at
ome with her. Of the 461 target children in the study,
69 of the sons or daughters had a diagnosis of DS. Of
hese cases, 2 were excluded from the present study as
hey had missing data on activities of daily living at Time
. The individuals with DS in the present study ranged
rom 15 to 56 years of age at Time 1 (mean � 31.61 years,
D � 7.19 years). The majority were daughters (60.5%),
nd 28.8% of mothers had at least a bachelor’s degree.
he majority of participants (92%) were white.

When this longitudinal study began, all of the
ndividuals with DS lived at home with their families.

owever, some individuals changed residences at
ach subsequent point in data collection, such that at
imes 4, 7, and 8, 94%, 81%, and 92% were co-residing
ith their families, respectively. Families who partici-
ated in all waves of data collection were not signifi-
antly different from families with missing data on child
ex, but families of older individuals were more likely to
nd study participation than families of younger individ-
als (F � 6.94, p � .05). As with the ASD sample, there
as no association between complete study participation

nd Time 1 daily living skills scores.

Procedure and Measures
Procedures and measures were identical for both the

ASD and DS samples. At each time point (Times 1, 4,

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DEVELOPMENTAL TRAJECTORIES AND AUTISM

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7, and 8), mothers completed self-administered ques-
tionnaires and participated in a 2- to 3-hour in-home
interview. For the ASD sample, data collection be-
tween Times 1 and 4 occurred an average of 5.00 years
apart. Approximately 3.45 years occurred between
Times 4 and 7, and 1.99 years occurred between Times
7 and 8. For the DS sample, an average of 4.44 years
elapsed between Times 1 and 4, 4.47 years between
Times 4 and 7, and 1.72 years between Times 7 and 8.

Independence in activities of daily living was mea-
sured using the Waisman Activities of Daily Living
Scale (W-ADL; Maenner, Smith, Hong, Makuch,
Greenberg, and Seltzer, unpublished data, 2011) (Table
1). Parent respondents rated their son or daughter’s
level of independence on 17 items covering the do-
mains of personal care, housekeeping, and meal-
related activities. Each item was rated on a three-point
scale of independence 0 (does not perform the task at
all), 1 (performs the task with help), or 2 (performs the
task independently); and items were summed. Coeffi-

TABLE 1 Waisman Activities of Daily Living Scale

1. Making his/her own bed
2. Doing household tasks, including picking up around the

house, putting things away, light housecleaning, etc.
3. Doing errands, including shopping in stores
4. Doing home repairs, including simple repairs around

the house, non-technical in nature; for example,
changing light bulbs or repairing a loose screw

5. Doing laundry, washing and drying
6. Washing/bathing
7. Grooming, brushing teeth, combing and/or brushing

hair
8. Dressing and undressing
9. Toileting

10. Preparing simple foods requiring no mixing or cooking,
including sandwiches, cold cereal, etc.

11. Mixing and cooking simple foods, fry eggs, make
pancakes, heat food in microwave, etc.

12. Preparing complete meal
13. Setting and clearing table
14. Drinking from a cup
15. Eating from a plate
16. Washing dishes (including using a dishwasher)
17. Banking and managing daily finances, including

keeping track of cash, checking account, paying bills,
etc. (Note: if he/she can do a portion but not all circle
‘1’ with help.)

Note: Instructions that accompanied the items: “Next we would like to
know about your son or daughter’s current level of independence in
performing activities of daily living. For each activity please tell me the
number which best describes your son/daughter’s ability to do the
task. For example, Independent would mean your son/daughter is
able to do the task without any help or assistance.”
2 � independent or does on own; 1 � does with help; 0 � does not

do at all.

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cient � values for the total score in the ASD sample
ranged from 0.90 to 0.94 for Times 1, 4, 7, and 8; for the
DS sample, the � values ranged from 0.91 to 0.93.

Child characteristics of age (continuous) and ID
status (1 � yes, 0 � no) were included as predictors of

aily living skills scores in the ASD sample analyses.
rocedures for assessing the presence of ID in our
ample have been reported in detail in previous stud-
es24 and involved a clinical consensus process using
nformation drawn from sources including direct cog-
itive testing and educational records. Residential sta-

us (0 � co-residing with parent, 1 � not co-residing
ith parent) was also included as a time-varying

ovariate.

Data Analysis
To address our primary aim, we used latent growth
curve (LGC) modeling to examine daily living skills
over a 10-year period. LGC modeling integrates indi-
vidual growth modeling (i.e., hierarchical linear mod-
eling) and structural equation modeling (SEM) ap-
proaches25 and provides estimates of mean structure
intercept and slope), reflecting the average starting
oint for all individuals and average rate of change.26

It is also possible to model nonlinear change; by
adding a quadratic parameter to a model that already
includes an intercept and linear slope, the growth
trajectory becomes curvilinear. In a purely linear
model, the rate of change is presumed to be constant
over time; in contrast, a quadratic latent curve model
allows the rate of change either to increase or decrease
over time. As an example, the magnitude of change in
repeated measures may be larger in earlier years than
in later years.26 The addition of a quadratic trend also
lters the interpretation of the linear slope, such that
he linear slope coefficient is changed to reflect the
nstantaneous rate of change at a specific point in
ime.25 If the coefficient for the quadratic factor is
egative, then the trajectory is concave to the time axis.
onversely, the presence of a positive quadratic trend

ndicates that the trajectory is convex to the time axis.25

After preliminary analyses of variance confirmed
the presence of change over time in daily living skills
without controlling for age and ID status, a multivar-
iate LCG model was assessed in which age and ID
status were included as time-invariant predictors and
residential status was included as a time-varying co-
variate. To address our secondary aim of providing an
illustrative benchmark for interpreting the patterns of
daily living skills observed in our ASD sample, we
used LGC modeling to assess change in daily living
skills in a sample of individuals with DS over a similar
period of time. All models were evaluated in terms of
measures of goodness-of-fit using the Mplus modeling
program.27 A satisfactory fit is indicated by a compar-
ative fit index (CFI) close to one and a root mean
square error of approximation (RMSEA) less than or

equal to 0.08.

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SMITH et al.
RESULTS
Primary Aim: Daily Living Skills in Adolescents
and Adults With ASD
Activities of daily living were assessed at 4 time
points (Times 1, 4, 7, and 8) in the ASD sample.
We present means, standard deviations, ranges,
and intercorrelations among study variables in
Table 2. Figure 1 depicts a mixed-effects regres-
sion model showing individual scores by age and
intellectual disability status. By the end of the
study, the average score for the group was 20.59
(SD � 8.08) on a scale in which a score of 34
reflects complete independence. Only 16.5% of
the sample had scores of 30 or above at Time 8.
Scores at each time point were significantly cor-
related with scores at all other time points.

We evaluated an LGC model of daily living
skills that specified quadratic growth over time
and included age and ID status as predictors of
all latent factors. Residential status (co-residing
vs not co-residing) also was included as a time-
varying covariate (Figure 2). In this model, the
latent intercept, linear slope, and quadratic trend
were indicated by daily living scores at Times 1,
4, 7, and 8. The factor loadings for the intercept
factor were all set to 1. The loadings for the linear
slope factor were fixed at 0, 5.0, 8.45, and 10.44,
reflecting the average length of time between
waves of data collection. The loadings for the
quadratic slope factor were the linear values
squared.

This model displayed excellent fit [�2 (15, n �
406)� 12.69, p � .63; RMSEA� 0.00; CFI � 1.0].
There was a significant positive linear slope (est. �
1.25, SE� 0.19, p�.001) and a significant negative
quadratic trend (est.� �0.07, SE� 0.02, p � .001).
However, the linear trend in a model that in-
cludes a quadratic trend is interpreted as the
instantaneous rate of change. This means that for
different snapshots of time, the rate of change
may be different. As such, to determine how
daily living skills were changing across time, we
also examined the values for the linear slope
when time was centered at Times 4, 7, and 8,
respectively. At Time 4, the linear trend was
positive (est.� 0.56, SE� 0.07, p�.001), but at
Time 7 the linear trend was nonsignificant (est. �
0.07, SE �0.15, p � .57). At Time 8, however,
there was a significant negative linear trend
(est.� �0.89, SE� 0.27, p � .001). Taken together,
these findings suggest that, on average, scores
were increasing at Times 1 and 4 but were no

longer significantly changing at Time 7. By Time

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TA

T T T T C ID M R N *

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8, scores were beginning to decrease. In other
words, daily living skills were improving during
adolescence and the early 20s, plateaued around
the time of the late 20s, and started to decline
during the early 30s. However, we encourage
some caution in interpreting the exact nature of
change for older individuals, as the majority
of the sample was under the age of 30 at the end
of the study.

There also were significant relationships be-
tween age, ID status, and the latent factors. Age
was positively associated with the intercept of
daily living skills, with older individuals having
higher scores at the start of the study (��0.24, p
� .001). Age also was associated with the linear
factor (� � �0.31, p � .01) and the quadratic
factor (� � 0.22, p � .10), although this associa-
tion with the quadratic factor was not significant
at the .05 level. These age effects suggest that
older individuals displayed a faster rate of cur-
vature; that is, they were declining at a faster

FIGURE 1 Change in Waisman Activities of Daily Livin
sample, individual and group trajectories. Note: Quadrat
rate. In addition, ID status was a significant s

JOURNAL OF THE AMERICAN ACADEMY OF CHILD & ADOLESCENT PSYCHIATRY
VOLUME 51 NUMBER 6 JUNE 2012

ded for Anonymous User (n/a) at Florida International University – Florida state con
For personal use only. No other uses without permission. Copyright
predictor of the intercept of daily living skills,
with individuals with ID having lower initial
levels of daily living skills at the start of the study
(�� �0.52, p � .001). Having an ID was also

egatively associated with the linear factor (� �
�0.20, p � .01), suggesting that individuals with
D were gaining skills at a slower rate than
ndividuals without ID. Residential status was a
tatistically significant covariate of daily living
kills at Times 1 and 8, with coresidence between
arent and child associated with lower scores.

econdary Aim: Daily Living Skills in Individuals
ith Down Syndrome

o explore trajectories of daily living skills in the
S sample, daily living skills were assessed at

our time points (Times 1, 4, 7, and 8). We present
eans, standard deviations, ranges, and intercor-

elations among study variables in Table 3. Fig-
re 3 depicts a mixed-effects regression model

-ADL) scores over time for autism spectrum disorder
ge2) mixed-model paramaterizations displayed.
g (W
ic (a
howing individual scores by age. By the end of

627www.jaacap.org
sortium from ClinicalKey.com by Elsevier on January 04, 2018.

©2018. Elsevier Inc. All rights reserved.

1
T
S
l
a
I
p
q

w
s
p
l
a
f
c

SMITH et al.
the study, the average score for the group was
23.83 (SD � 6.33) on a scale in which a score of 34
reflects complete independence. Only 19.6% of
the sample had scores of 30 or above at Time 8.
Scores at each time point were significantly cor-
related with scores at all other time points.

FIGURE 2 Latent growth curve model of Waisman
Activities of Daily Living (ADL) scores for individuals with
autism spectrum disorders (N � 397). Note: ID �
intellectual disability. *p � .05, ��p � .01, ���p �
.001, †p � .10.

TABLE 3 Descriptive Statistics and Intercorrelations Amo

Time 1 W-ADL Time 4 W-ADL

Time 1 W-ADL 1 (n � 166)
Time 4 W-ADL 0.88*** (n � 124) 1 (n � 125)
Time 7 W-ADL 0.83*** (n � 98) 0.88*** (n � …

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