Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder that typically manifests in early childhood
as impaired social communication and restricted, repetitive behaviors which falls as a spectrum from mild to
severe. In the past 5 decades, ASD has gone from a narrowly defined, rare disorder of childhood onset to a wellresearched,
life-long condition which is relatively common and heterogeneous .The prevalence of ASD has been
increasing in the United States over the last two decades, which is most likely related to change in diagnostic
criteria, increased public awareness , and improved screening. The prognosis of ASD today is much brighter
than it was in the past and more people with the condition are able to speak, read and live independently in
the community. Early diagnosis is very important as early intensive behavioral interventions have shown to
improve functional outcomes and quality of life. Comprehensive, multidisciplinary evaluation is needed for the
diagnosis of ASD which should include the use of standardized measures as the Autism Diagnostic Interview-
Revised and the Autism Diagnostic Observation Schedule-second edition. High rate of medical and psychiatric
comorbidity have seen in individuals with ASD including epilepsy, depression, anxiety, and sleep difficulties.
Early and intensive behavior interventions have shown to be beneficial in improving social communication,
language and play. Pharmacological treatment is indicated for psychiatric comorbidity such as attention-deficit
hyperactivity disorder, emotional dysregulation, irritability and aggression.
“Autism” derived from the Greek word “autos, or “self”, refers to
someone who lives in a world of his own. Leo Kanner [1], first introduced
the term autism as a diagnostic label to define a specific syndrome
in young children characterized by early onset of impaired social
and emotional relationship. Since then, autism is now recognized
as Autism Spectrum Disorder (ASD) which is a neurodevelopmental
disorder defined by social communication impairments and restricted,
repetitive behaviors [2,3]. Early diagnosis is important because
early diagnosis and early intensive behavioral intervention programs
have been shown to improve functional outcomes and quality of life
[4,5]. Unfortunately, early diagnosis of ASD can be challenging and
despite much earlier concerns by caregivers for possible ASD, it is
often diagnosed after the age of three [6,7]. The challenges in early
diagnosis might be related to complexity and heterogeneity of ASD,
leading to different presentations of individuals with ASD. ASD is
also associated with significant psychiatric and medical comorbidity
including language disorder, intellectual disability, sleep problems,
anxiety, depression, obsessive compulsive disorder, attention deficit
hyperactivity disorder and epilepsy [8-10]. The exact etiology of ASD
is unknown but it is thought to have strong and complex genetic underpinnings
with environmental factors modulating the phenotypic
expression [11,12].
Among eight years old in the U.S., the prevalence is 2.3% in 2018
compared to 1.8% in 2008 with male to female ratio of 4:1 [13]. Black
children with ASD tend to present at older ages than white children
and often present with intellectual disability [14]. Several factors have
likely contributed to the increased prevalence rate which includes
change in the diagnostic criteria, increased awareness and increased
access to services [15-19]. Children who often receive a late diagnosis
include: females, ethnic minorities, low socioeconomic status, those
from families who do not English, and those without language delay
[20]. There is a concern that females are under-diagnosed and diagnosed at later age because of the belief that ASD occurs primarily in
males [21]. There is also a possibility that the current diagnostic procedures
are less sensitive to the presence of ASD among females or
that females are more able to minimize ASD symptoms including social
communication impairment (via camouflaging) [22,23]. Camouflaging
can, for example, include suppression of repetitive movement,
forcibly sustained eye contact or the use of learnt formulaic phrases
[24].
The key diagnostic features of ASD include deficit in social communication
and restricted, repetitive pattern of behavior, interest, or
activities. The presenting symptoms of ASD depend on age, language
level, and cognitive functions. Some signs and symptoms of ASD may
present between 6 and 12 months of age but reliable diagnosis, in
many cases, can be made around 24 months of age [25,26]. Spoken
language delay and social deficit are the most prominent features in
children with ASD who are younger than three years old. Language
delay without compensatory pointing or gesturing might help to
differentiate ASD from expressive language delay [27,28]. The inability
to coordinate one’s own attention between another person
and distant object to share attention (joint attention) by 15 months
of age should indicate the need for ASD evaluation [27,28]. Repetitive
behavior and restricted range of interest may be less apparent
in younger children. Many children with ASD have several coexisting
conditions that impact the presentation and the level of impairment.
The prevalence of ASD is higher in individuals with special health
needs including people with visual impairment, hearing impairment,
intellectual disability, and Fragile-X Syndrome [29-31]. Furthermore,
psychiatric and medical comorbidity are very common in ASD population,
particularly attention deficit hyperactivity disorder, anxiety,
depression, aggression, self-injury, sleep difficulties, feeding problem
and epilepsy [32-36]. Additionally, almost 30% of people with ASD
present with special skills that exceed what seems humanly possible
(savant skills) most commonly manifesting in mental arithmetic, art,
and memory skills [37,38].
Many public health systems have attempted to identify very young
children with ASD in the general population. However, screening tools
have not been sensitive enough to effectively identify most of children
with ASD in the general population in whom parents have not been
already recognized a delay [39]. When parent have expressed concern,
screening instruments become effective for predicting ASD in
children as young as 18 months of age [40]. The American Academy
of Pediatrics recommends that all children be screened for ASD at
18 and 24 months of age [41]. The modified-checklist for autism in
toddlers, revised (M-CHAT-R), a 20 item screening questionnaire, is
one of the frequently used ASD screening tools in primary care settings.
It is designed to identify children 16 to 30 months who are at
risk for ASD [42]. Children who have a positive screening test for ASD
should undergo a comprehensive evaluation and referral for developmental
services. Children who receive consistent pediatric care, are
in frequent contact with grandmothers, and who have older siblings
receive earlier diagnoses than those who do not [43,44].
For definitive diagnosis of ASD, a comprehensive assessment by
a multidisciplinary team using standardized diagnostic tools to exclude
other conditions, identifying any comorbid conditions and to
assess the child’s overall level of function [45-47]. The most widely
used diagnostic tools for ASD are the Autism Diagnostic Observation
Schedule, second edition (ADOS-2) and the Autism Diagnostic Interview,
Revised (ADI-R) [48]. The American Academy of Pediatrics and
The American College of Medical Genetics and Genomics recommend
genetic testing for individuals diagnosed with ASD [49]. In particular,
chromosomal microarray is recommended to scan the genome
for copy number variants. Adults seeking first diagnosis of ASD are
typically have comorbid psychiatric disorders but are not intellectually
disabled [50]. While brief self-reports do not have adequate specificity,
versions of ADOS, and Social Responsiveness Scale (SRS) are
appropriate for verbally fluent adults [51,52].
74-93% of ASD risk is heritable [53]. Models for genetic risk in
ASD propose that complex inheritance with additive contributions
from common variants that individually make small contributions
to risk as well as rare variants that have larger effect sizes [54]. Several
environmental risk factors have also been identified including
advanced maternal or paternal age, prenatal valproic acid exposure,
preterm birth, low birth weight, small for gestational age status, and
large for gestational age status [55-58].
Early behavioral intervention for at least 25 hours per week is
recommended for young children with ASD [59]. Applied Behavioral
Analysis is the cornerstone for early intensive behavioral interventions,
which utilize applied behavior analytic principles of learning
to teach children the appropriate skills in natural settings, have been
shown to improve children’s language, play, and social communications
[60,61]. Cognitive behavioral therapy can be very effective in
reducing anxiety and depressive symptoms in individuals with ASD
[62]. In school-age children without intellectual disabilities, social
skills training can be useful in improving social skills and emotional
dysfunctions [63]. Providing behavioral, speech, occupational and
physical therapy in the school setting together with parent training
resulted in improved language skills and decreased disruptive behavior
in children with ASD [64].
No medication is available to target core symptoms of ASD, but
medications can be useful to target specific maladaptive behaviors
which did not respond to intensive behavioral therapy. In addition
medications can be useful to target comorbid psychiatric conditions
[27]. Risperidone and aripiprazole have shown to improve symptoms
of irritability and agitation in children and adolescents with ASD and
are the only medications approved by the U.S. Food and Drug Administration
for the treatment of ASD-Associated Irritability [65,66]. Psychostimulants
(methylphenidate) and non-stimulants (atomoxetine
and guanfacine) have shown to be effective in the management of
ADHD symptoms in individuals with ASD [67]. Melatonin may also be
useful for sleep disturbances [68]. The current evidence does not support
the use of any supplement for the treatment of core ASD symptoms
but N-acetylcysteine and sulforaphane have demonstrated some
efficacy for behavioral and emotional symptoms associated with ASD
[69].
Current studies show that there has been a significant improvement
in outcomes of individuals with ASD in the current studies compared
to the old data [70]. However, adults with ASD continue to be
less likely to live independently or be employed and more likely to use
mental health services compared to individuals without ASD diagnosis
[71]. Better outcomes are reported in individuals with ASD with
higher cognitive abilities, had earlier referrals, more intensive early
behavioral interventions and fewer pharmacological interventions
[72,73]. Mortality rates are approximately 2-fold higher for individuals
with ASD compared to general populations and suicide rates are
much higher in this population compared to the general population
[74,75].
Life for many children and adults with ASD have improved compared
to when autism was first described by Leo Kanner. More individuals
with ASD can talk, read, graduate from school and live independently.
ASD affect over 2% of children and adults in the U.S.
The evidence continues to support early intensive behavioral interventions
delivered by a multidisciplinary team as a first-line therapy,
while comorbid mental health conditions such as ADHD, anxiety and
aggression may be treated by specific behavioral therapy or medicine.
Mayes SD, Zickgraf H (2019) Atypical eating behaviors in children and adolescents with autism, ADHD, other disorders, and typical development. Res Autism Spectr Disord 64: 76-83.
ISSN: 2574 -1241
Abstract
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