Autism in the School-Aged Child: Diagnostic Dilemma, Comorbid Condition—or Both?

Eastern Virginia Medical School

Dr Harrington is professor of pediatrics at Eastern Virginia Medical School and division director of general academic pediatrics at Children’s Hospital of The King’s Daughters in Norfolk, Va.

Author's note: Recently, my local television station chose my son with autism for their Student Athlete of the Week. He is a swimmer at his high school. I thought readers might enjoy viewing this video about him.

ABSTRACT: For diagnosing autism spectrum disorder (ASD), the Diagnostic Statistical Manual of Mental Disorders, Fifth Edition has added a caveat that “symptoms may not become fully manifest until social demands exceed limited capacities.”Recognizing ASD in older children can be challenging for the clinician, educator, and parent. The use of the Childhood Autism Screening Test may prove helpful in screening school-aged children for ASD. Some children with ASD will not have a diagnosis by the time they reach elementary school but may have been alternatively “labeled” as having behavioral concerns, social anxiety, or a learning disorder. The differential diagnosis for ASD is broad and consists of biological disorders and transient conditions. Biological disorders (genetic or metabolic disorders, deafness or hearing difficulties, heavy metal poisoning) can be evaluated objectively and ruled out on the basis of physical examination findings and test results, whereas transient conditions (post-traumatic stress disorder, child abuse, and mutism) generally can be identified over time after the child has had counseling and therapy. Comorbid conditions can highlight the most difficult aspects of ASD and can sometimes be more stigmatizing or socially isolating than autism. Of the different co-occurring conditions of ASD, anxieties/phobias and obsessive compulsive disorder (OCD) tend to be more common. Anxiety, attention-deficit/hyperactivity disorder, and disruptive behaviors are more likely to occur in elementary-school-aged children with ASD, and OCD is more often diagnosed in tweens and adolescents with ASD.

Author’s note: Autism spectrum disorder and autism will be used interchangeably in this article.



The American Academy of Pediatrics (AAP) has recommended that all 18- and 24-month-old children be screened for an autism spectrum disorder (ASD).1 Screening at these ages helps pediatric practitioners provide an early diagnosis of autism, which allows parents to access intensive behavioral treatments (ie, applied behavioral analysis) that can improve a child’s overall outcome in language, adaptive behaviors, academic performance, and IQ.2,3

Although research has confirmed that the diagnosis of an ASD can reliably be made in the second year of life, the stability of that diagnosis may lessen into the school years and beyond. This has been especially the case in children with a diagnosis of Asperger syndrome or pervasive developmental disorder-not otherwise specified (PDD-NOS).4

In this article, I review changes that will occur in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V), the screening tools used to identify ASD at different ages, and the differential diagnoses to consider in the evaluation of the child with behavioral concerns or a learning disorder. I also discuss the comorbid conditions most commonly associated with ASD, which can sometimes complicate the diagnosis and treatment of ASD in school-aged children.


Despite some debate about the proposed changes in the DSM-V scheduled for publication in May of 2013, the new ASD diagnostic criteria will hopefully be able to provide a comprehensive and stable diagnosis for children with ASD. Table 1 shows the pertinent changes to the DSM-V criteria compared with the DSM-IV-TR criteria. The new edition merges the communication and social interaction categories into one symptom category and increases the importance of repetitive and restrictive behaviors. In addition, a severity level for functional impairment in autism will be utilized. This will include 3 severity levels for 2 categories:

•Social communication.

•Restricted interests and repetitive

Level 1, being the least severe, will describe patients requiring support; level 3, the most severe, will describe those requiring very substantial support.

For diagnosing ASD, the DSM-V has added a caveat that symptoms may not become fully manifest until social demands exceed limited capacities.

autism diagnosis


As we move forward and primary care practitioners are called upon to provide care to children and adolescents with autism, they will also need to become more familiar with the available neurodevelopmental and mental health screening tools. This will in turn help provide timely screening, earlier diagnosis, and a comprehensive medical home for children with ASD.

The AAP’s Autism Toolkit—developed to support pediatricians and other health care professionals in the screening and identification, along with ongoing management of ASD in children—provides 3 autism screening tools to be used at different ages. In regard to these tools, the AAP states that “no tool is perfect and inclusion of these tools does not imply AAP endorsement; they were chosen because of their easy accessibility and reliability based on current available research.” Table 2 highlights the salient features of the screening devices.5-9


As stated earlier, the DSM-V will subsume all the previous classifications of autism (eg, autistic disorder, PDD-NOS, and Asperger syndrome) into ASD with severity functional levels. Autistic disorder, which likely would be categorized as an ASD and a severity of level 3, is easier to diagnose by 2 years of age; whereas, identifying lower severity functional levels of ASD, such as Asperger disorder and PDD-NOS, may take longer and may have less stability over time. In fact, a current diagnosis of ASD at age 2 years may change by age 7 years in up to 25% of patients.4

ASD may initially be missed in a child who speaks well and has a minimal degree of intellectual disability. Recognizing ASD in older children can be challenging for the clinician, educator, and parent. The use of the Childhood Autism Screening Test (CAST) may prove helpful in screening schoolchildren for ASD.

CAST consists of 37 yes/no questions related to social abilities and interest in being around others. For each ASD-relevant response, 1 point is scored, with a score of 15 or higher being positive and a maximum score of 31. Although only a screening test, CAST results can be helpful when responding to concerns by teachers and parents and when considering a second level proprietary screen, such as the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview Revised (ADIR).

autism screening


Some children with ASD will not have a diagnosis by the time they reach elementary school but may have been alternatively “labeled” as having behavioral concerns (such as hyperactivity, inattention, aggressiveness, mood disturbances) or a learning disorder.10 In some instances, children who were initially given a diagnosis of ASD may have another disorder that explains the reason for their behavior or they may lose the diagnosis over time, naturally or through therapy, and no longer meet the criteria for classification.

The differential diagnosis of ASD can include, but is not limited to, the following conditions:

•Genetic disorders.11

•Metabolic disorders.11

•Deafness or hearing difficulties.12,13

•Heavy metal poisoning.14

•Post-traumatic stress disorder.15

•Reactive attachment disorder.15

•Child abuse.15


These conditions can be misdiagnosed as ASD, or they may be related to ASD itself. They should be considered when making the diagnosis of ASD. Conceptually, it may be best to consider the differential diagnoses in 2 groupings: biological disorders and transient conditions.

Biological disorders. Genetic disorders that may be associated with ASD include monogenic disorders, such as fragile X syndrome, neurofibromatosis type 1, Rett syndrome, Down syndrome, myotonic dystrophy, and tuberous sclerosis. Although quite rare, the metabolic disorders phenylketonuria, organic acidemia, and mitochondrial disease should be considered when diagnosing ASD.

Because a genetic “syndrome” is typically a constellation of findings, one would say a child has Down syndrome and ASD, not the reverse. However, one may diagnose ASD, and after genetic testing find that the child has fragile X syndrome. It may also be that as more sophisticated testing with comparative genomic hybridization arrays are performed, deletions and duplications significantly associated with ASD may be detected.

In general, genetic and metabolic disorders are associated with autism and significant intellectual dysfunction, so the dilemma is in how to discern a diagnosis that explains ASD at a fairly early age. Toriello11 provides a helpful review on the approach one can take when considering a genetic or metabolic illness in a child with autism.

Deafness or hearing difficulties may cause some confusion early on, even when a child has frequent ear infections that may be contributing to hearing deficits. For this reason, it is very important to order a hearing assessment early in the process when evaluating a child who may have autism. This can be difficult and may ultimately require a sedated auditory brainstem response or a brainstem auditory evoked-response test.1

Heavy metal poisoning refers mostly to the relationship of autism with lead, as the evidence for other heavy metals causing autism is inconclusive. Lead poisoningwas considered a causative factor for autism at one point.14 However, children with autism tend to have a prolonged oral fixation phase, which increases the risk of lead poisoning. This is one reason why the AAP recommends lead testing for children with any developmental delay.

Biological conditions can be evaluated objectively and ruled out on the basis of physical examination findings and test results, including genetic and serological testing, urinalysis, biopsy, and audiology testing.

Transient conditions. Post-traumatic stress disorder, reactive attachment disorder, child abuse, and mutism generally can be identified over time after you have followed the child and he or she has had counseling and therapy. These conditions may require 6 months to 1 year to discern. A diagnosis of autism should be withheld until the child can be maintained in a stable environment.


It is helpful to be aware of the many co-occurring diagnoses of ASD. The following list of comorbid conditions is not meant to be all inclusive. ASD can present with a comorbid condition or a comorbid condition can manifest later, and children may have more than one comorbid condition. A co-occurring illness may sometimes be diagnosed before ASD. The comorbid condition can highlight the most difficult aspect of ASD and can be more stigmatizing or socially isolating than

The conditions most likely to coincide with a diagnosis of ASD and functional severity level 3 in young children are:

•Intellectual disability.

•Language delay.

•Learning disability.

Common co-occurring disorders in elementary school-aged children with ASD are:

•Anxiety (general, separation, panic,
agoraphobia, social).

•Attention-deficit/hyperactivity disorder (ADHD).

•Disruptive behaviors.

The following comorbid disorders are more likely to be diagnosed in tweens and adolescents with ASD:

•Obsessive compulsive disorder (OCD).

•Depression or dysthymia.

•Bipolar disorder and schizophrenia.

Anxiety and phobias. Anxieties and phobias are found in essentially half of all children with an ASD diagnosis. The majority of children have more than one phobia and/or anxiety related to objects or situations.17 The Spence Children’s Anxiety Scale can help determine whether the child has separation or generalized anxiety, along with social phobia and panic disorders. The Screen for Child Anxiety Related Disorders is a child and parent self-report used to identify 5 types of anxiety: general anxiety, separation anxiety, social phobia, school phobia, and physical symptoms of anxiety.

OCD. OCD is considered the second most common co-occurring condition with ASD and, in many cases, defines early behaviors in children based on their unwillingness to change routines. Over one third of children with ASD continue to have some type of obsession or compulsion that will limit their ability to interact socially. These behaviors are fairly easy to ask parents about and may not require any specific screening.

ADHD. ADHD is another very common co-occurring condition in children with ASD. Using the inclusive definition of all types of ADHD, ADHD can be diagnosed in up to 62% of children with ASD.18 Often, children with ADHD are treated with stimulants, such as methylphenidates or amphetamines, before a diagnosis of ASD is ever made. Some studies have even expressed the idea that ADHD may actually be considered somewhere along the continuum of the autism spectrum.19

The Vanderbilt Assessment Scales and Follow-up forms (for parents and teachers) can be helpful for evaluating children with ASD and suspected ADHD. These can be downloaded from the National Initiative for Children’s Healthcare Quality web site. The important caveat for children with autism who have ADHD is that they may be more likely to have side effects to ADHD medications than children without ASD. Therefore, the mantra is to “start low and go slow” with ADHD medications.

Depression. One point at which depression may manifest in older children with ASD is when they become more aware of their isolation and differences. In middle school, the pressure to conform is strong and there is a low tolerance for being different. Children with ASD may feel different, or worse, may be teased and taunted and find it difficult to fit in. They may begin to withdraw, and the early signs of moodiness and depression may develop if they feel they do not relate to a specific peer group.

The Pediatric Symptom Checklist (PSC) is sometimes useful for an overall screen in patients who may have more than one co-occurring disorder. It comes in 2 versions: the PSC-17 short form or longer form PSC-35.

Disruptive behaviors. Disruptive behavior generally encompasses aggression, self-injurious behaviors, and conduct problems that put the child at odds with teachers, assistants, peers, and parents. These behaviors may cause suspension from school and may not respond initially to behavioral therapy. This may also be the first time there is a consideration to treat with an antipsychotic medication, such as risperidone or aripiprazole.20 However, it is very important to  perform a thorough evaluation to identify and assess target behaviors before launching into pharmacological management. Myers and colleagues21 provide a comprehensive table that reviews the clinical approach to pharmacological management.

Bipolar disorder and schizophrenia. A recent retrospective review found a fairly strong association between autistic traits and later psychotic experiences in adolescence.22 Some children with ASD may cycle rapidly through their rages and have a decreased need for sleep along with a manic-like hyperactivity. If you are concerned about a bipolar diagnosis, it is best to refer the child to a psychiatrist for assessment and support. Children with autism have also been noted to speak to themselves and may have an “internal” conversation. However, if a child/adolescent with autism starts hearing voices or becomes delusional, consider that these may be the first manifestations of schizophrenia. This diagnosis also requires support from our psychiatric colleagues. 


A child with a language delay or learning disability may improve over time. The child in whom communication and socialization skills improve, and in whom restrictive and repetitive behaviors decrease, may no longer meet the criteria for ASD. This loss of an ASD diagnosis, or change along the continuum of an ASD diagnosis, has also been seen with children who have had significant intellectual disability as well. Factors that seemed to affect children who make rapid gains were higher socio-economic class, having a well-educated mother, and white race. Studying these trajectories in a longitudinal way may help us target specific interventions and improve treatment for all children with ASD.23

In some cases, as the child with ASD ages, a comorbid, or co-occurring, disorder may become the defining diagnosis and he may not actually have autism. These co-occurring disorders were more likely to be related to learning disabilities, speech/hearing problems, or moderate/severe anxiety.24


Pediatricians are on the front lines for autism screening, evaluation, diagnosis, and management. To provide a comprehensive medical home, clinicians will require more training and more experience with longitudinal follow-up of children with ASD. This will, in turn, help  affected children and families reach their full potential.