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March 7, 2025

Updated Analysis of ADHD Prevalence in The United States

The National Health Interview Survey (NHIS) is conducted annually by the National Center for Health Statistics at the Centers for Disease Control and Prevention. The NHIS is done primarily through face-to-face computer-assisted interviews in the homes of respondents. But telephone interviews are substituted on request, or where travel distances make in-home visits impractical.  

For each interviewed family, only one sample child is randomly selected by a computer program.  

The total number of households with a child or adolescent aged 3-17 for the years 2018 through 2021 was 26,422. 

Based on responses from family members, 9.5% of the children and adolescents randomly surveyed throughout the United States had ADHD.  

This proportion varied significantly based on age, rising from 1.5% for ages 3-5 to 9.6% for ages 6-11 and to 13.4% for ages 12-17. 

There was an almost two-to-one gap between the 12.4% prevalence among males and the 6.6% prevalence among females. 

There was significant variation by race/ethnicity. While rates among non-Hispanic whites (11.1%) and non-Hispanic blacks (10.5%) did not differ significantly, these two groups differed significantly from Hispanics (7.2%) and Others (6.6%). 

There were no significant variations in ADHD prevalence based on highest education level of family members. 

But family income had a significant relationship with ADHD prevalence, especially at lower incomes. For family incomes under the poverty line, the prevalence was 12.7%. That dropped to 10.3% for family incomes above the poverty level but less than twice that level. For all others it dropped further to about 8.5%. Although that might seem like poverty causes ADHD, we cannot draw that conclusion.  Other data indicate that adults with ADHD have lower incomes.  That would lead to more ADHD in kids from lower income families.

There was also significant geographic variation in reported prevalence rates. It was highest in the South, at 11.3%, then the Midwest at 10%, the Northeast at 9.1%, with a jump down to 6.9% in the West. 

Overall ADHD prevalence did not vary significantly by year over the four years covered by this study. 

Study Conclusion:

This study highlights a consistently high prevalence of developmental disabilities among U.S. children and adolescents, with notable increases in other developmental delays and co-occurring learning and intellectual disabilities from 2018 to 2021. While the overall prevalence remained stable, these findings emphasize the need for continued research into potential risk factors and targeted interventions to address developmental challenges in youth.

It is also important to note that this study assessed the prevalence of ADHD being diagnosed by healthcare professionals.  Due to variations in healthcare accessibility across the country, the true prevalence of ADHD may differ still.

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Are you struggling to get the care you need to manage your ADHD? Support The ADHD Evidence Project and get this step-by-step guide to getting the treatment you deserve: https://bit.ly/41gIQE9

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What Can Doctors Do About Those Faking ADHD?

What can Doctors do about Fake ADHD?

ADHD is a serious disorder that requires treatment to prevent many adverse outcomes. But, because the diagnosis of ADHD is based on how the patient responds to questions, people can pretend that they have ADHD when they do not. If you Google "fake ADHD" you'll get many pages of links, including a Psychology Today article on the topic and bloggers describing how they were able to fool doctors into giving them ADHD medications. Is fake ADHD a serious problem? Not really. The Internetseems to be faking an epidemic of fake ADHD.I say that because we have decades of research that show many objective measures of abnormality and impairment in people who say they have ADHD. These include traffic accidents, abnormalities in brain imaging, and molecular genetic differences. Some studies even suggest that ADHD adults downplay their ADHD symptoms. For example, one study diagnosed ADHD in children and then contacted them many years later when they were young adults.When they were interviewed as young adults, their responses to questions about ADHD suggested that they did not have the disorder. But when the same questions about the patient were asked to someone who lived with the patient as a young adult, it was clear that they still had ADHD. So rather than faking ADHD, many ADHD adults do not recognize that they have symptoms of the disorder. That said, we also know from research studies that, when asked to pretend that they have ADHD, adults can fake the disorder. That means that they can learn about the symptoms of the disorder and makeup examples of how they have had them when they have not. The research discussed above suggests that this is not common, but we do know that some people have motives for faking ADHD.For example, some college students seek special accommodations for taking tests; others may want stimulants for abuse, misuse, or diversion. Fortunately, doctors can detect fake ADHD in several ways. If an adult itself-referred for ADHD and asks specifically for stimulant medication, that raises the possibility of fake ADHD and drug-seeking. Because the issue of stimulant misuse has been mostly a concern on college campuses, many doctors treating college students will require independent verification of the patient's ADHD symptoms by speaking with a parent, even over the phone if an in-person visit is not possible. Using ADHD rating scales will not detect fake ADHD, and it is easy to fake poor performance on tests of reading or math ability. Neuropsychological tests can sometimes be used to detect malingering, but require referral to a specialist. Researchers are developing methods to detect faking ADHD symptoms. These have shown some utility in studies of young adults, but are not ready for clinical practice. So, currently, doctors concerned about fake ADHD should look for objective indicators of impairment (e.g., documented traffic accidents; academic performance below expectation) and speak to a parent of the patient to document that impairing symptoms of the disorder were present before the age of twelve. Because the issue of fake ADHD is of most concern on college campuses, it can also be helpful to speak with a teacher who has had frequent contact with the patient. In an era of large lecture halls and broadcast lectures, that may be difficult. And don't be fooled by the Internet. We don't want to deny treatment to ADHD patients out of undocumented reports of an epidemic of fake ADHD.

April 27, 2021
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Attention Deficit Hyperactivity Disorder: Fact vs. Fiction

Attention Deficit Hyperactivity Disorder: Fact vs. Fiction

Many myths have been manufactured about attention deficit hyperactivity disorder (ADHD).  Facts that are clear and compelling to most scientists and doctors have been distorted or discarded from popular media discussions of the disorder.   Sometimes, the popular media seems motivated by the maxim "Never let the facts get in the way of a good story."  That's fine for storytellers, but it is not acceptable for serious and useful discussions about ADHD.

Myths about ADHD are easy to find.  These myths have confused patients and parents and undermined the ability of professionals to appropriately treat the disorder.   When patients or parents get the idea that the diagnosis of ADHD is a subjective invention of doctors, or that ADHD medications cause drug abuse, that makes it less likely they will seek treatment and will increase their chances of having adverse outcomes. 

Fortunately, as John Adams famously said of the Boston Massacre, "Facts are stubborn things."  And science is a stubborn enterprise; it does not tolerate shoddy research or opinions not supported by fact.   ADHD scientists have addressed many of the myths about the disorder in the International Consensus Statement on ADHD, a published summary of scientific facts about ADHD endorsed by 75 international ADHD scientists in2002.  The statement describes evidence for the validity of ADHD, the existence of genetic and neurobiological causes for the disorder, and the range and severity of impairments caused by the disorder.   

The Statement makes several key points:

  • The     U.S. Surgeon General, the American Medical Association, the American     Psychiatric Association, the American Academy of Child and Adolescent Psychiatry, the     American Psychological Association, and the American Academy of Pediatrics recognize ADHD as a valid disorder.
  • ADHD     involves a serious deficiency in a set of psychological abilities, and these deficiencies pose serious harm to most individuals possessing the disorder.
  • Many studies show that the psychological deficits in people with ADHD are associated with abnormalities in several specific brain regions.
  • The genetic contribution to ADHD is routinely found to be among the highest for any psychiatric disorder.
  • ADHD     is not a benign disorder. For those it afflicts, it can cause devastating problems.

The facts about ADHD will prevail if you take the time to learn about them. This can be difficult when faced with a media blitz of information and misinformation about the disorder. In future blogs, I'll separate the fact from the fiction by addressing several popular myths about ADHD.

April 25, 2021
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What is Evidenced-Based Medicine?

What is Evidenced-Based Medicine?

With the growth of the Internet, we are flooded with information about attention deficit hyperactivity disorder from many sources, most of which aim to provide useful and compelling "facts" about the disorder.  But, for the cautious reader, separating fact from opinion can be difficult when writers have not spelled out how they have come to decide that the information they present is factual. 

My blog has several guidelines to reassure readers that the information they read about ADHD is up-to-date and dependable. They are as follows:

Nearly all the information presented is based on peer-reviewed publications in the scientific literature about ADHD. "Peer-reviewed" means that other scientists read the article and made suggestions for changes and approved that it was of sufficient quality for publication. I say "nearly all" because in some cases I've used books or other information published by colleagues who have a reputation for high-quality science.

When expressing certainty about putative facts, I am guided by the principles of evidence-based medicine, which recognizes that the degree to which we can be certain about the truth of scientific statements depends on several features of the scientific papers used to justify the statements, such as the number of studies available and the quality of the individual studies. For example, compare these two types of studies.  One study gives drug X to 10 ADHD patients and reported that 7 improved.  Another gave drug Y to 100 patients and a placebo to 100 other patients and used statistics to show that the rate of improvement was significantly greater in the drug-treated group. The second study is much better and much larger, so we should be more confident in its conclusions. The rules of evidence are fairly complex and can be viewed at the Oxford Center for Evidenced Based Medicine (OCEBM;http://www.cebm.net/).


The evidenced-based approach incorporates two types of information: a) the quality of the evidence and b) the magnitude of the treatment effect. The OCEBM levels of evidence quality are defined as follows (higher numbers are better:

  1. Mechanism-based reasoning.  For example, some data suggest that oxidative stress leads to ADHD, and we know that omega-3 fatty acids reduce oxidative stress. So there is a reasonable mechanism whereby omega-3 therapy might help ADHD people.
  2. Studies of one or a few people without a control group, or studies that compare treated patients to those that were not treated in the past.

Non-randomized, controlled studies.    In these studies, the treatment group is compared to a group that receives a placebo treatment, which is a fake treatment not expected to work.  

  1. Non-randomized means that the comparison might be confounded by having placed different types of patients in the treatment and control groups.
  2. A single randomized trial.  This type of study is not confounded.
  3. Systematic review and meta-analysis of randomized trials. This means that many randomized trials have been completed and someone has combined them to reach a more accurate conclusion.

It is possible to have high-quality evidence proving that a treatment works but the treatment might not work very well. So it is important to consider the magnitude of the treatment effect, also called the "effect size" by statisticians. For ADHD, it is easiest to think about ranking treatments on a ten-point scale. The stimulant medications have a quality rating of 5 and also have the strongest magnitude of effect, about 9 or 10.Omega-3 fatty acid supplementation 'works' with a quality rating of 5, but the score for the magnitude of the effect is only 2, so it doesn't work very well. We have to take into account patient or parent preferences, comorbid conditions, prior response to treatment, and other issues when choosing a treatment for a specific patient, but we can only use an evidence-based approach when deciding which treatments are well-supported as helpful for a disorder.

April 23, 2021
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How do Stimulants Modulate the Brain to Improve ADHD Symptoms?

How do Stimulants Modulate the Brain to Improve ADHD Symptoms?

The stimulants methylphenidate and amphetamine are well known for their efficacy in treating symptoms of ADHD in both youth and adults.   Although these medications have been used for several decades, relatively little is known about the mechanisms of action that lead to their therapeutic effect.    

New data about the mechanism comes from a meta-analysis by Katya Rubia and colleagues. They analyzed 14 functional magnetic resonance imaging (fMRI) data sets comprising 212 youth with ADHD.  Each of these data sets assessed the short-term effects of stimulants on fMRI-assessed brain activations. In the fMRI paradigm, ADHD and control participants are asked to do a neurocognitive task while the activity of their brains is being measured. Dr. Rubia and colleagues analyzed data from fMRI assessments of time discrimination, inhibition, and working memory, each of which is known to be deficient in ADHD patients.    

The meta-analysis found that the most consistent brain activations were seen in a region comprising the right inferior frontal cortex(IFC) and insula, even when the analysis was limited to previously medication-naïve patients. The implicated region of the brain is known to mediate cognitive control, time estimation, and attention.  Dr.Rubia also notes that other studies show that the IFC/Insula is needed for updating information and allocating attention to relevant stimuli.  

Another region implicate by the meta-analysis was the right putamen, a region that is rich in dopamine transporters. This finding is consistent with the fact that the dopamine transporter is the main target of stimulant medications.    

What is the potential clinical implication of these findings?  As Dr. Rubia and colleagues note, it is possible that the fMRI anomalies they identified could be used as a biomarker for ADHD or a biomarker to select patients who should respond optimally to stimulant medication. Although fMRI cannot be used as a clinical tool at this time, research of this sort is opening up new horizons for how we understand the etiology of ADHD and the mechanisms whereby medications exert their effects.

April 21, 2021
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Cognitive Behavioral Therapy for ADHD: What is it? Does it work?

Cognitive Behavioral Therapy for ADHD: What is it? Does it work?

Cognitive Behavioral Therapy (CBT) is a one-to-one therapy, for adolescents or adults, where a therapist teaches an ADHD patient how thoughts, feelings, and behaviors are all interrelated and how each of these elements affects the others.  CBT emphasizes cognition or thinking because a major goal of this therapy is to help patients identify thinking patterns that lead to problem behaviors.  For example, the therapist might discover that the patient frequently has negative automatic thoughts such as "I'm stupid" in challenging situations. We call the thought 'automatic' because it invades the patient's consciousness without any effort. Thinking "I'm stupid" can cause anxiety and depression, which leads to failure. Thus, stopping the automatic thought will modify this chain of events and, hopefully, improve the outcome from failure to success.

CBT also educates patients about their ADHD and how it affects them in important daily activities.


For example, most ADHD patients need help with activity schedules, socializing, organizing their workspace, and controlling their distractibility. By teaching specific cognitive and behavioral skills, the therapist helps the patient deal with their ADHD symptoms productively. For example, some ADHD patients are very impulsive when conversing with others. They don't wait their turn during conversations and may blurt out irrelevant ideas. This can be annoying to others, especially in the context of school or business relationships. The CBT therapist helps the patient identify these behaviors and creates strategies for avoiding them.

So, does CBT work for ADHD? The evidence base is small, but when CBT has been used for adult ADHD, it has produced positive results in well-designed studies.   These studies typically compare patients taking ADHD medications with those taking ADHD medications and receiving CBT.  

So for now, it is best to consider CBT as an adjunct rather than a replacement for medication. There are even fewer studies of CBT for adolescents with ADHD.  These initial studies also suggest that CBT will be useful for adolescents with ADHD who are also taking ADHD medications.  Some data suggest that CBT can be successfully applied in the classroom, but the evidence base is very small.

How can this information be used by doctors and patients for treatment planning?  Current treatment guidelines suggest starting with an ADHD medication.  After a suitable medication and dose are found, the patient and doctor should determine if any problems remain.  If so, CBT should be considered an adjunct to ADHD medications.

April 19, 2021
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Is Cognitive Behavior Therapy Effective for Treating Adult ADHD?

Is Cognitive Behavior Therapy Effective for Treating Adult ADHD?

The term "cognitive behavior therapy (CBT)" refers to a type of talk therapy that seeks to change the way patients think about themselves, their disorder, and the world around them in a manner that will help them overcome symptoms and achieve life goals.

Because CBT is typically administered by a psychologist or other mental health professionals, CBT services are not available in primary care. Nonetheless, it is useful for primary care practitioners to know about CBT so that they can refer appropriately as needed. So, what can we say about the efficacy of CBT for treating adults with ADHD?

Based on a meta-analysis by Young and colleagues, we know for certain that the number of published trials of CBT for adult ADHD is small; only nine trials are available. Five of these compared CBT with waiting list controls; three compared CBT with appropriate placebo control groups. In all of these studies, patients in the CBT and control groups were also being treated with ADHD medications.

Thus, they speak to the efficacy of CBT when given as an adjunctive treatment. The meta-analysis examined the waiting list controlled studies and the placebo-controlled studies separately. For both types of study, the effect of CBT in reducing ADHD symptoms was statistically significant, with a standardized mean effect size of 0.4.

This effect size, albeit modest, is large enough to conclude that CBT will be useful for some patients being treated with ADHD medications. Given these results, a reasonable guideline would be to refer adults with ADHD to a CBT therapist if they are being maintained on an ADHD medication, but that medication is not leading to a complete remission of their symptoms and impairments. So listen to your patients. If, while on an appropriately titrated medication regime, they still complain about unresolved symptoms or impairments, you need to take action.  In some cases, changing their dose or shifting to another medication will be useful. If such approaches fail or are not feasible, you should consider referral to a CBT therapist.

April 17, 2021
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Can ADHD be a Deadly Disorder?

Can ADHD be a Deadly Disorder?

In the world of research, it is unusual for a single study to be definitive. A possible exception is a recent report in the highly esteemed Lancet, which concluded that people diagnosed with ADHD were about two times more likely to die early than people without ADHD. The data came from the medical registers of Denmark that include1.92 a million people, of which 32,061 have ADHD. The registers included the times and causes of deaths spanning 32 years.

It is a remarkable resource. We know that people with very severe ADHD are at high risk for substance use disorders and antisocial behaviors. In the Danish study, these disorders also increased the risk for premature death, but the risk was even higher if people with those disorders also had ADHD. ADHD also increased the risk for early death among people without these extra problems. This latter finding points to an ADHD-specific pathway to premature death. What is it?  Well, we know that ADHD people are at risk for injuries, traffic accidents, and traumatic brain injury.  We don't know for certain why, but two symptom clusters of ADHD, inattention, and impulsivity, would be expected to increase the risk for accidents and injuries. For example, adults who are distracted while driving are clearly at risk for accidents. Accidents accounted for most of the early deaths in the Danish study. But the study also found an increase in natural causes of death due to having ADHD. This may be due to the well-replicated association between ADHD and obesity, or the possibility that ADHD symptoms lead to poor health habits.

In the Danish study, the mean age at diagnosis was 12.3, which means that many of the ADHD people in the study were not treated for many years after the onset of symptoms. The risk for early death increased with the age at diagnosis. This suggests that failing to diagnose and treat ADHD early makes the disorder worse and increases the risk for the types of behaviors that lead to premature death. Will these data change public policy or clinician behavior? I hope so. Perhaps the media will stop trivializing ADHD and accept it as a bona fide disorder in need of early identification and treatment.  Policymakers should allocate ADHD people their fair share of healthcare and research resources. For clinicians, early identification and treatment should become the rule rather than the exception.

Talk of premature death will worry parents and patients. That is understandable, but such worries can be alleviated by focusing on two facts: the absolute risk for premature death is low, and this risk can be greatly reduced by seeking and adhering to evidence-based treatments for the disorder.

April 13, 2021
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A Brief History of ADHD

A Brief History of ADHD

I have too often seen on the Internet or media the statement that ADHD is a recent invention of psychiatrists and/or pharmaceutical companies. Such statements ignore the long history of ADHD that my colleague and I reviewed in our "Primer" about ADHD.  

ADHD has a long history. The first ADHD syndrome was described in a German medical textbook by Weikard in 1775. That's not a typo. The ADHD syndrome had been identified before the birth of the USA. Dr.Weikard did not use the term ADD or ADHD, yet he described a syndrome of hyperactivity and inattention that corresponds to what we call ADHD today.  

ADHD-like syndromes were described in Scotland in 1798 and in France in the late 19th century. The first description of an ADHD-like syndrome in a medical journal was by Dr. George Still in 1901 who described what he called a 'defect of moral control' in The Lancet. The discovery that stimulant drugs are effective in treating ADHD occurred in 1937 when Dr. Charles Bradley discovered that Benzedrine (an amphetamine compound) improved the behavior of children diagnosed with behavioral disorders. In subsequent years, several terms were used to describe children with ADHD symptoms. Examples are Kramer-Pollnow syndrome, minimal brain damage, minimal brain dysfunction, and hyperkinetic reaction.  

,It was not until the 1980s that the term Attention Deficit Disorder (ADD) came into widespread use with the publication of the American Psychiatric Association's Diagnostic and Statistical Manual (DSM).   During the ensuing decades, several changes were made to the diagnostic criteria and the term ADD was replaced with ADHD so as not to overemphasize either inattention or hyperactivity when diagnosing the disorder. And, as the graphic below describes, these new and better diagnostic criteria led to many breakthroughs in our understanding of the nature of the disorder and the efficacy of treatments. So, if you think that ADHD is an invention of contemporary society, think again. It has been with us for quite some time.

April 11, 2021
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The Goal of ADHD Diagnosis? Safe and Effective Treatment

The Goal of ADHD Diagnosis? Safe and Effective Treatment

The diagnosis of ADHD should only be done by a licensed clinician, and that clinician should have one goal in mind: to plan a safe and effective course of evidence-based treatment. The infographic gives a summary of this diagnostic approach which my colleagues and I prepared for our "Primer" about ADHD,http://rdcu.be/gYyV.  A key point that parents of ADHD youth and adults with ADHD should keep in mind is that there is only one way to diagnose ADHD.An expert clinician must document the criteria for the disorder as specified by either the Diagnostic and Statistical Manual of the American Psychiatric Association, which is now in its fifth edition (DSM-5), or the World Health Organization's International Classification of Diseases (ICD-10). The two sets of criteria are nearly identical. These criteria are most commonly applied by a clinician asking questions of the parent (for children) and/or patient (for adolescents and adults).For children, information from the teacher can be useful. Some clinicians get this information by having the parent ask the teacher to fill out a rating scale. This information can be very useful if it is available.  When diagnosing adults, it is also useful to collect information from a significant other, which can be a parent for young adults or a spouse for older adults. But when such informants are not available, diagnosing ADHD based on the patient's self-report is valid. As the infographic indicates, any diagnosis of ADHD should also assess for comorbid psychiatric disorders, as these have implications for which ADHD medications will be safe and effective. And because a prior history of cardiovascular disease or seizures frequently contraindicate stimulants. These must also be assessed.

April 9, 2021
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Adult Onset ADHD: Does it Exist? Is it Distinct from Youth Onset ADHD?

Adult Onset ADHD: Does it Exist? Is it Distinct from Youth Onset ADHD?

There is a growing interest (and controversy) in 'adult-onset ADHD. No current diagnostic system allows for the diagnosis of ADHD in adulthood, yet clinicians sometimes face adults who meet all criteria for ADHD, except for age at onset. Although many of these clinically referred adult-onset cases may reflect poor recall, several recent longitudinal population studies have claimed to detect cases of adult-onset ADHD that showed no signs of ADHD as a youth (Agnew-Blais, Polanczyk et al. 2016, Caye, Rocha, et al. 2016). They conclude, not only that ADHD can onset in adulthood, but that childhood-onset and adult-onset ADHD may be distinct syndromes(Moffitt, Houts, et al. 2015)

In each study, the prevalence of adult-onset ADHD was much larger than the prevalence of childhood-onset adult ADHD). These estimates should be viewed with caution.  The adults in two of the studies were 18-19 years old.  That is too small a slice of adulthood to draw firm conclusions. As discussed elsewhere (Faraone and Biederman 2016), the claims for adult-onset ADHD are all based on population as opposed to clinical studies.
Population studies are plagued by the "false positive paradox", which states that, even when false positive rates are low, many or even most diagnoses in a population study can be false.  

Another problem is that the false positive rate is sensitive to the method of diagnosis. The child diagnoses in the studies claiming the existence of adult-onset ADHDused reports from parents and/or teachers but the adult diagnoses were based on self-report. Self-reports of ADHD in adults are less reliable than informant reports, which raises concerns about measurement error.   Another longitudinal study found that current symptoms of ADHD were under-reported by adults who had had ADHD in childhood and over-reported by adults who did not have ADHD in childhood(Sibley, Pelham, et al. 2012).   These issues strongly suggest that the studies claiming the existence of adult-onset ADHD underestimated the prevalence of persistent ADHD and overestimated the prevalence of adult-onset ADHD.  Thus, we cannot yet accept the conclusion that most adults referred to clinicians with ADHD symptoms will not have a history of ADHD in youth.

The new papers conclude that child and adult ADHD are "distinct syndromes", "that adult ADHD is more complex than a straightforward continuation of the childhood disorder" and that adult ADHD is "not a neurodevelopmental disorder". These conclusions are provocative, suggesting a paradigm shift in how we view adulthood and childhood ADHD.   Yet they seem premature.  In these studies, people were categorized as adult-onset ADHD if full-threshold add had not been diagnosed in childhood.  Yet, in all of these population studies, there was substantial evidence that the adult-onset cases were not neurotypical in adulthood (Faraone and Biederman 2016).  Notably, in a study of referred cases, one-third of late adolescent and adult-onset cases had childhood histories of ODD, CD, and school failure(Chandra, Biederman, et al. 2016).   Thus, many of the "adult onsets" of ADHD appear to have had neurodevelopmental roots. 

Looking through a more parsimonious lens, Faraone and Biederman(2016)proposed that the putative cases of adult-onset ADHD reflect the existence of subthreshold childhood ADHD that emerges with full threshold diagnostic criteria in adulthood.   Other work shows that subthreshold ADHD in childhood predicts onsets of full-threshold ADHD in adolescence(Lecendreux, Konofal, et al. 2015).   Why is onset delayed in subthreshold cases? One possibility is that intellectual and social supports help subthreshold ADHD youth compensate in early life, with decompensation occurring when supports are removed in adulthood or the challenges of life increase.  A related possibility is that the subthreshold cases are at the lower end of a dimensional liability spectrum that indexes risk for onset of ADHD symptoms and impairments.  This is consistent with the idea that ADHD is an extreme form of a dimensional trait, which is supported by twin and molecular genetic studies(Larsson, Anckarsater, et al. 2012, Lee, Ripke, et al. 2013).  These data suggest that disorders emerge when risk factors accumulate over time to exceed a threshold.  Those with lower levels of risk at birth will take longer to accumulate sufficient risk factors and longer to onset.

In conclusion, it is premature to accept the idea that there exists an adult-onset form of ADHD that does not have its roots in neurodevelopment and is not expressed in childhood.   It is, however, the right time to carefully study apparent cases of adult-onset ADHD to test the idea that they are late manifestations of a subthreshold childhood condition.

April 7, 2021
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