Autism and ADHD Overlap (What a New Study Says About Genetics)



Study of Siblings Shows Elevated ADHD and Autism Risks


A recent study has shown that younger siblings of children with ADHD and autism are far more likely to develop one of those conditions.

Younger siblings of children with autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) are at greater risk of developing those conditions.

A recent study published in JAMA Pediatrics found the odds of a sibling — born after a child diagnosed with ASD — being diagnosed with the same condition were 30 times higher than that of later-born siblings of non-diagnosed children.

The odds of a younger sibling of a child with ASD being diagnosed with ADHD were also 3.7 times higher when compared with siblings of non-diagnosed children.

For younger siblings of a child with ADHD, the odds of being diagnosed with the same condition were 13 times higher when compared with siblings of nondiagnosed children.

The odds of an ASD diagnosis for this group were 4.4 times higher.

Meghan Miller, PhD, author of the study and assistant professor in the Department of Psychiatry and Behavioral Sciences and at the UC Davis MIND Institute reported:


“Compared to younger siblings of non-diagnosed children, we found that younger siblings of children with ASD were more likely to be diagnosed with ASD themselves, which is consistent with prior research.”


“Also, as expected, we found that younger siblings of children with ADHD were more likely to be diagnosed with ADHD themselves. Perhaps most intriguingly, we found that younger siblings of children with ASD were at elevated risk for ADHD, and that younger siblings of children with ADHD were at elevated risk for ASD compared to younger siblings of nondiagnosed children.”


Shared Genetic Risk Factors


ADHD and ASD are thought to share various genetic risk factors.


Miller and her colleagues examined medical records from 730 younger siblings of children living with ADHD and 158 later-born siblings of children living with ASD.

They also examined the records of 14,287 younger siblings of children without any known diagnosis.

ADHD and ASD are thought to share various genetic risk factors. Miller says previous research has shown the rates of a child having both ADHD and ASD are as high as 70 percent.


Miller’s research supports the idea that ADHD and ASD may share underlying causes and are highly inheritable.


“Prior research has strongly suggested genetic links between ASD and ADHD, based on the high comorbidity rates between these two conditions and evidence of shared heritability of the disorders and their symptoms. The research on specific overlapping genetic markers is mixed, and there is still much to be learned about the ways in which these two disorders are linked,” Miller said.


Same Disorder, Different Manifestations?


ADHD and ASD may be different manifestation of the same overarching disorder.


Children or adults living with ADHD may be hyperactive, compulsive, and have trouble paying attention.

ASD is characterized by problems with social, communication, or emotional skills. Children and adults living with ASD may behave, interact, and learn in ways that are notably different from others. They may struggle with a change in routine and may repeat certain behaviors.

Dr. Rolanda Gott, a developmental-behavioral pediatrician at the University of California Los Angeles Mattel Children’s Hospital, isn’t surprised by the findings of Miller’s study.  She says:


“ADHD and ASD may be different manifestation of the same overarching disorder that may manifest differently in multiple family members. Many genes affect multiple brain functions and it is more common that we see both ASD and ADHD than ASD alone.”


“Many ADHD kids struggle with social skills deficits, inflexibility, sensory processing difficulties that are overlapping with ASD symptoms,” she added. “Both disorders are on a continuous spectrum and many times it is hard to draw the line between pure ADHD that also affects social communication and behavior versus ADHD plus ASD.”


Monitor and Intervene Early


Early intervention is important for children with ASD and ADHD.


Although ASD and ADHD may appear differently, Miller’s research highlights the overlapping risk of the conditions for younger siblings as well as the importance of early monitoring.

Geraldine Dawson, PhD, director of the Duke Center for Autism and Brain Development says:

“These findings suggest that younger siblings of children with ASD and ADHD should be monitored and screened for both disorders. We know that early intervention is important for children with ASD and those with ADHD.”


Siblings of children with ASD and ADHD should be monitored and screened for both disorders.


Scott Kollins, PhD, is a professor of psychiatry and behavioral sciences and director of the Duke ADHD Program. He says although much is known about the risk factors for both ADHD and ASD, there is still a lot to discover about the underlying causes of these conditions.

“There are many known genetic and non-genetic risk factors for both ASD and ADHD, including many common genetic variants, premature and/or low birthweight, and medical problems early in life. However, each of these known factors only contributes a very small amount of risk for having the disorders, so their actual clinical utility is limited.” he added.


No Medical Tests For ASD or ADHD


Diagnosis is based on behavior and development.


There’s no medical test to diagnose ASD. A diagnosis is made when a doctor looks at the behavior and development of a child.

Autism can be detected at 18 months, and by the time a child is 2, a diagnosis from an experienced doctor is very reliable.

However, many children are not diagnosed with ASD until they’re much older, and the delay in diagnosis means they may miss out on early help.

Similarly, there’s no single test for the diagnosis of ADHD. A diagnosis is made after an assessment of behavior against a set of criteria.


Should Parents Worry?

Well-child doctor visits should include autism screening.

David Mandell, ScD, associate director of the Center for Autism Research at the Children’s Hospital of Philadelphia, says monitoring of younger siblings is important and may also explain the level of diagnosis in this group.

“Younger children in families in which the older child has ADHD or ASD likely are subject to greater scrutiny. They may be more likely to get the diagnosis just because of increased surveillance, and the symptom bar may be lower than it is in other families,” Mandell says.

Although Miller’s research suggests a heightened risk for younger siblings, she says families with children who have the conditions who intend to have more children shouldn’t be worried.

“It’s important to note that most of the younger siblings of children with autism or ADHD did not receive diagnoses. So, although risk is increased among these younger siblings, most do not develop autism or ADHD.

We suggest that more careful monitoring of younger siblings of diagnosed children may be useful so that, if signs or symptoms do begin to emerge, these younger siblings can be referred for early intervention as early as possible,” she said.


Does Your Child Have ADHD?

There is no single test that can be used to diagnose attention deficit hyperactivity disorder in children and adults it’s diagnosed after a person has shown some or all of the symptoms of ADHD on a regular basis for more than six months.


In addition, symptoms must be present in more than one setting and have been present since before the age of 12.


Depending on the number and type of symptoms, a person will be diagnosed with one of three subtypes of ADHD: Primarily Inattentive, Primarily Hyperactive or Combined subtype.


Diagnosing ADHD in Children

Health care providers, such as pediatricians, psychiatrists, and child psychologists, can diagnose ADHD with the help of standard guidelines from the American Academy of Pediatrics or the American Psychiatric Association’s Diagnostic and Statistical Manual (DSM).


The diagnosis involves gathering information from several sources, including schools, caregivers, and parents.


The health care provider will consider how a child’s behavior compares with that of other children the same age, and he or she may use standardized rating scales to document these behaviors.



ADHD Symptoms

Some symptoms that suggest ADHD in children include inattention, hyperactivity, and/or impulsivity.

Many children with ADHD:

  • Are in constant motion
  • Squirm and fidget
  • Make careless mistakes
  • Often lose things
  • Do not seem to listen
  • Are easily distracted
  • Do not finish tasks

To diagnose ADHD, your child should receive a full physical exam, including vision and hearing screenings.

Also, the FDA has approved the use of the Neuropsychiatric EEG-Based Assessment Aid (NEBA) System, a noninvasive scan that measures theta and beta brain waves. The theta/beta ratio has been shown to be higher in children and adolescents with ADHD than in children without it.

The scan, approved for use in those aged 6 to 17 years, is meant to be used as a part of a complete medical and psychological exam.


Conditions That Mimic ADHD

The health care provider should take a complete medical history to screen for other conditions that may affect a child’s behavior. Certain conditions that could mimic ADHD or cause the ADHD-like behaviors are:

  • Recent major life changes (such as divorce, a death in the family, or a recent move)
  • Undetected seizures
  • Thyroid problems
  • Sleep problems
  • Anxiety
  • Depression
  • Lead toxicity


Does Your Child Have Autism Spectrum Disorder?

Diagnosing autism spectrum disorder (ASD) can be difficult, since again, there is no medical test for it. Doctors look at the child’s behavior and development to make a diagnosis.

ASD can sometimes be detected at 18 months or younger. By age 2, a diagnosis by an experienced professional can be considered very reliable. 

However, many children do not receive a final diagnosis until much older. This delay means that children with an ASD might not get the help they need.

Diagnosing an ASD takes two steps:

  • Developmental Screening
  • Comprehensive Diagnostic Evaluation


Developmental Screening For Autism

Developmental screening is a short test to tell if children are learning basic skills when they should, or if they might have delays.

During developmental screening, the doctor might ask the parent some questions or talk and play with the child during an exam to see how she learns, speaks, behaves, and moves. A delay in any of these areas could be a sign of a problem.

All children should be screened for developmental delays and disabilities during regular well-child doctor visits.

It’s important for doctors to screen all children for developmental delays, but especially to monitor those who are at a higher risk for developmental problems due to preterm birth, low birth weight, or having a brother or sister with an ASD.


Schedule Well-Child Doctor Visits at:
  • 9 months
  • 18 months
  • 24 or 30 months
  • Additional screening might be needed if a child is at high risk for developmental problems due to preterm birth, low birth weight or other reasons.


In addition, all children should be screened specifically for ASD during regular well-child doctor visits at specific intervals.


Screen Specifically for ASD at:
  • 18 months
  • 24 months
  • Additional screening might be needed if a child is at high risk for ASD (e.g., having a sister, brother or other family member with an ASD) or if behaviors sometimes associated with ASD are present


If your child’s doctor does not routinely check your child with this type of developmental screening test, ask that it be done.


If the doctor sees any signs of a problem, a comprehensive diagnostic evaluation is needed.


Full Diagnostic Evaluation For Autism

The second step of diagnosis is a comprehensive evaluation. This thorough review may include looking at the child’s behavior and development and interviewing the parents.

The full evaluation may also include a hearing and vision screening, genetic testing, neurological testing, and other medical testing.

In some cases, the primary care doctor might choose to refer the child and family to a specialist for further assessment and diagnosis.

Specialists who can do this type of evaluation include:

  • Developmental Pediatricians (doctors who have special training in child development and children with special needs)
  • Child Neurologists (doctors who work on the brain, spine, and nerves)
  • Child Psychologists or Psychiatrists (doctors who know about the human mind)


Recommended Book For Parents of an ADHD Child

Finally Focused provides proven natural and medical methods to easily treat problems such as nutritional deficiencies or excesses, dysbiosis (a microbial imbalance inside the body), sleeping difficulties, and food allergies, all of which surprisingly can cause or worsen the symptoms of ADHD.

Using Dr. Greenblatt’s effective Plus-Minus Healing Plan, parents will first understand the reasons behind their child’s symptoms, and then be able to eliminate them by addressing the child’s unique pattern of biological weakness. 

And if conventional medication is still necessary, this integrative approach will minimize or even eliminate troublesome side effects. Using Dr. Greenblatt’s expert advice, millions of children and adults with ADHD finally will get the help they need to achieve true wellness.


Recommended Book For Parents of an Autistic Child

Many tens of thousands of parents have found the facts they need about high-functioning autism spectrum disorder (ASD), including Asperger syndrome, in this indispensable guide.

In A Parent’s Guide to High-Functioning Autism Spectrum Disorder, leading experts show how you can work with your child’s unique impairments–and harness his or her capabilities.

Vivid stories and real-world examples illustrate ways to help kids with ASD relate more comfortably to peers, learn the rules of appropriate behavior, and succeed in school.

You’ll learn how ASD is diagnosed and what treatments and educational supports really work.

This second edition is updated with the latest research and resources, the second edition clearly explains the implications of the DSM-5 diagnostic changes.

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